MOLCAS manual: Bibliography 1 Björn O. Roos, Valera Veryazov, and Per-Olof Widmark. Relativistic atomic natural orbital type basis sets for the alkaline and alkaline-earth atoms applied to the ground-state potentials for the corresponding dimers. Theor. Chem. Acc., 111:345–351, 2004. 2 Björn O. Roos, Roland Lindh, Per-Åke Malmqvist, Valera Veryazov, and Per-Olof Widmark. Main group atoms and dimers studied with a new relativistic ANO basis set. J. Phys. Chem. A, 108:2851–2858, 2004. 3 Björn O. Roos, Roland Lindh, Per-Åke Malmqvist, Valera Veryazov, and Per-Olof Widmark. New relativistic ANO basis sets for transition metal atoms. J. Phys. Chem. A, 109:6575–6579, 2005. 4 Björn O. Roos, Roland Lindh, Per-Åke Malmqvist, Valera Veryazov, and Per-Olof Widmark. New relativistic ANO basis sets for actinide atoms. Chem. Phys. Letters, 409:295–299, 2005. 5 Björn O. Roos, Roland Lindh, Per-Åke Malmqvist, Valera Veryazov, Per-Olof Widmark, and Antonio Carlos Borin. New relativistic atomic natural orbital basis sets for lanthanide atoms with applications to the $\ce{Ce}$ diatom and $\ce{LuF3}$. J. Phys. Chem. A, 112:11431–11435, 2008. 6 Björn O. Roos, Per-Åke Malmqvist, and Laura Gagliardi. Heavy element quantum chemistry – the multiconfigurational approach. In Erkki J. Brändas and Eugene S. Kryachko, editors, Fundamental World of Quantum Chemistry. Vol. II, pages 425–442. Kluwer Academic Publishers, Dordrecht, Netherlands, 2003. 7 Francesco Aquilante, Roland Lindh, and Thomas Bondo Pedersen. Unbiased auxiliary basis sets for accurate two-electron integral approximations. J. Chem. Phys., 127:114107, 2007. 8 Francesco Aquilante, Per-Åke Malmqvist, Thomas Bondo Pedersen, Abhik Ghosh, and Björn O. Roos. Cholesky decomposition-based multiconfiguration second-order perturbation theory (CD-CASPT2): Application to the spin-state energetics of $\ce{Co^{III}(diiminato)(NPh)}$. J. Chem. Theory Comput., 4:694–702, 2008. 9 Francesco Aquilante, Thomas Bondo Pedersen, Björn O. Roos, Alfredo Sánchez de Merás, and Henrik Koch. Accurate ab initio density fitting for multiconfigurational self-consistent field methods. J. Chem. Phys., 129:024113, 2008. 10 Quan Manh Phung, Sebastian Wouters, and Kristine Pierloot. Cumulant approximated second-order perturbation theory based on the density matrix renormalization group for transition metal complexes: A benchmark study. J. Chem. Theory Comput., 12(9):4352–4361, 2016. 11 Sebastian Wouters, Veronique Van Speybroeck, and Dimitri Van Neck. DMRG-CASPT2 study of the longitudinal static second hyperpolarizability of all-trans polyenes. J. Chem. Phys., 145(5):054120, 2016. 12 Naoki Nakatani and Sheng Guo. Density matrix renormalization group (DMRG) method as a common tool for large active-space CASSCF/CASPT2 calculations. J. Chem. Phys., 146(9):094102, 2017. 13 Dongxia Ma, Giovanni Li Manni, and Laura Gagliardi. The generalized active space concept in multiconfigurational self-consistent field methods. J. Chem. Phys., 135:044128, 2011. 14 Björn O. Roos. The multiconfigurational (MC) self-consistent field (SCF) theory. In Björn O. Roos, editor, Lecture Notes in Quantum Chemistry. European Summer School in Quantum Chemistry, volume 58 of Lecture Notes in Chemistry, pages 177–254. Springer-Verlag, Berlin, Germany, 1992. 15 James Finley, Per-Åke Malmqvist, Björn O. Roos, and Luis Serrano-Andrés. The multi-state CASPT2 method. Chem. Phys. Letters, 288:299–306, 1998. 16 John D. Watts, Jürgen Gauss, and Rodney J. Bartlett. Coupled-cluster methods with noniterative triple excitations for restricted open-shell Hartree–Fock and other general single determinant reference functions. Energies and analytical gradients. J. Chem. Phys., 98:8718–8733, 1993. 17 Pavel Neogrády and Miroslav Urban. Spin-adapted restricted Hartree–Fock reference coupled-cluster theory for open-shell systems: Noniterative triples for noncanonical orbitals. Int. J. Quantum Chem., 55:187–203, 1995. 18 Roland Lindh. The reduced multiplication scheme of the Rys–Gauss quadrature for 1st order integral derivatives. Theor. Chim. Acta, 85:423–440, 1993. 19 Shervin Fatehi and Joseph E. Subotnik. Derivative couplings with built-in electron-translation factors: Application to benzene. J. Phys. Chem. Lett., 3(15):2039–2043, 2012. 20 Michael Stenrup, Roland Lindh, and Ignacio Fdez. Galván. Constrained numerical gradients and composite gradients: Practical tools for geometry optimization. J. Comput. Chem., 36(22):1698–1708, 2015. 21 Kerstin Andersson, Per-Åke Malmqvist, Björn O. Roos, Andrzej Sadlej, and Krzysztof Wolinski. Second-order perturbation theory with a CASSCF reference function. J. Phys. Chem., 94:5483–5486, 1990. 22 Kerstin Andersson, Per-Åke Malmqvist, and Björn O. Roos. Second-order perturbation theory with a complete active space self-consistent field reference function. J. Chem. Phys., 96:1218–1226, 1992. 23 Per Åke Malmqvist, Kristine Pierloot, Abdul Rehaman Moughal Shahi, Christopher J. Cramer, and Laura Gagliardi. The restricted active space followed by second-order perturbation theory method: Theory and application to the study of $\ce{CuO2}$ and $\ce{Cu2O2}$ systems. J. Chem. Phys., 128:204109, 2008. 24 Vicenta Sauri, Luis Serrano-Andrés, Abdul Rehaman Moughal Shahi, Laura Gagliardi, Steven Vancoillie, and Kristine Pierloot. Multiconfigurational second-order perturbation theory restricted active space (RASPT2) method for electronic excited states: A benchmark study. J. Chem. Theory Comput., 7:153–168, 2011. 25 Björn O. Roos, Markus P. Fülscher, Per-Åke Malmqvist, Manuela Merchán, and Luis Serrano-Andrés. Theoretical studies of the electronic spectra of organic molecules. In Stephen R. Langhoff, editor, Quantum Mechanical Electronic Structure Calculations with Chemical Accuracy, volume 13 of Understanding Chemical Reactivity, pages 357–438. Kluwer Academic Publishers, Dordrecht, Netherlands, 1995. 26 Björn O. Roos, Kerstin Andersson, Markus P. Fülscher, Per-Åke Malmqvist, Luis Serrano-Andrés, Kristine Pierloot, and Manuela Merchán. Multiconfigurational perturbation theory: Applications in electronic spectroscopy. In I. Prigogine and Stuart A. Rice, editors, New Methods in Computational Quantum Mechanics, volume 93 of Advances in Chemical Physics, pages 213–331. John Wiley & Sons, Hoboken, NJ, USA, 1996. 27 Kerstin Andersson and Björn O. Roos. Multiconfigurational second-order perturbation theory: A test of geometries and binding energies. Int. J. Quantum Chem., 45:591–607, 1993. 28 Giovanni Ghigo, Björn O. Roos, and Per-Åke Malmqvist. A modified definition of the zeroth-order Hamiltonian in multiconfigurational perturbation theory (CASPT2). Chem. Phys. Letters, 396:142–149, 2004. 29 K. Andersson. Different forms of the zeroth-order Hamiltonian in second-order perturbation theory with a complete active space self-consistent field reference function. Theor. Chim. Acta, 91:31–46, 1995. 30 Björn O. Roos and Kerstin Andersson. Multiconfigurational perturbation theory with level shift — the $\ce{Cr2}$ potential revisited. Chem. Phys. Letters, 245:215–223, 1995. 31 Björn O. Roos, Kerstin Andersson, Markus P. Fülscher, Luis Serrano-Andrés, Kristine Pierloot, Manuela Merchán, and Vicent Molina. Applications of level shift corrected perturbation theory in electronic spectroscopy. J. Mol. Struct. Theochem, 388:257–276, 1996. 32 Niclas Forsberg and Per-Åke Malmqvist. Multiconfiguration perturbation theory with imaginary level shift. Chem. Phys. Letters, 274:196–204, 1997. 33 Thorstein Thorsteinsson, David L. Cooper, Joseph Gerratt, Peter B. Karadakov, and Mario Raimondi. Modern valence bond representations of CASSCF wavefunctions. Theor. Chim. Acta, 93:343–366, 1996. 34 David L. Cooper, Thorstein Thorsteinsson, and Joseph Gerratt. Fully variational optimization of modern VB wave functions using the CASVB strategy. Int. J. Quantum Chem., 65:439–451, 1997. 35 David L. Cooper, Thorstein Thorsteinsson, and Joseph Gerratt. Modern VB representations of CASSCF wave functions and the fully-variational optimization of modern VB wave functions using the CASVB strategy. Adv. Quantum Chem., 32:51–67, 1998. 36 T. Thorsteinsson and D. L. Cooper. An overview of the CASVB approach to modern valence bond calculations. In Alfonso Hernández-Laguna, Jean Maruani, Roy McWeeny, and Stephen Wilson, editors, Quantum Systems in Chemistry and Physics. Vol. 1: Basic problems and models systems, pages 303–326. Kluwer Academic Publishers, Dordrecht, Netherlands, 2000. 37 Pavel Neogrády, Miroslav Urban, and Ivan Hubač. Spin adapted restricted Hartree–Fock reference coupled cluster theory for open shell systems. J. Chem. Phys., 100:3706–3716, 1994. 38 Pavel Neogrády, Miroslav Urban, and Ivan Hubač. Spin adapted restricted open shell coupled cluster theory. Linear version. J. Chem. Phys., 97:5074–5080, 1992. 39 Peter J. Knowles, Claudia Hampel, and Hans-Joachim Werner. Coupled cluster theory for high spin, open shell reference wave functions. J. Chem. Phys., 99:5219–5227, 1993. 40 Miroslav Urban, Jozef Noga, Samuel J. Cole, and Rodney J. Bartlett. Towards a full CCSDT model for electron correlation. J. Chem. Phys., 83:4041–4046, 1985. 41 Krishnan Raghavachari, Gary W. Trucks, John A. Pople, and Martin Head-Gordon. A fifth-order perturbation comparison of electron correlation theories. Chem. Phys. Letters, 157:479–483, 1989. 42 Reinhart Ahlrichs, Peter Scharf, and Claus Ehrhardt. The coupled pair functional (CPF). A size consistent modification of the CI(SD) based on an energy functional. J. Chem. Phys., 82:890–898, 1985. 43 Delano P. Chong and Stephen R. Langhoff. A modified coupled pair functional approach. J. Chem. Phys., 84:5606–5610, 1986. 44 Robert J. Gdanitz and Reinhart Ahlrichs. The averaged coupled-pair functional (ACPF): A size-extensive modification of MR CI(SD). Chem. Phys. Letters, 143:413–420, 1988. 45 B. Roos. A new method for large-scale CI calculations. Chem. Phys. Letters, 15:153–159, 1972. 46 Isaiah Shavitt. Graph theoretical concepts for the unitary group approach to the many-electron correlation problem. Int. J. Quantum Chem., 12-S11:131–148, 1977. 47 Per E. M. Siegbahn. Generalizations of the direct CI method based on the graphical unitary group approach. II. Single and double replacements from any set of reference configurations. J. Chem. Phys., 72:1647–1656, 1980. 48 William C. Swope, Hans C. Andersen, Peter H. Berens, and Kent R. Wilson. A computer simulation method for the calculation of equilibrium constants for the formation of physical clusters of molecules: Application to small water clusters. J. Chem. Phys., 76:637–649, 1982. 49 I. V. Abarenkov. Unit cell for a lattice electrostatic potential. Phys. Rev. B, 76:165127, 2007. 50 Peter V. Sushko and Igor V. Abarenkov. General purpose electrostatic embedding potential. J. Chem. Theory Comput., 6:1323–1333, 2010. 51 Jorge M. del Campo and Andreas M. Köster. A hierarchical transition state search algorithm. J. Chem. Phys., 129:024107, 2008. 52 Richard C. Raffenetti. General contraction of Gaussian atomic orbitals: Core, valence, polarization, and diffuse basis sets; molecular integral evaluation. J. Chem. Phys., 58:4452–4458, 1973. 53 Jan Almlöf and Peter R. Taylor. General contraction of Gaussian basis sets. I. Atomic natural orbitals for first- and second-row atoms. J. Chem. Phys., 86:4070–4077, 1987. 54 Per-Olof Widmark, Per-Åke Malmqvist, and Björn O. Roos. Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions. I. First row atoms. Theor. Chim. Acta, 77:291, 1990. 55 Per-Olof Widmark, B. Joakim Persson, and Björn O. Roos. Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions. II. Second row atoms. Theor. Chim. Acta, 79:419–432, 1991. 56 Rosendo Pou-Amérigo, Manuela Merchán, Ignacio Nebot-Gil, Per-Olof Widmark, and Björn O. Roos. Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions. III. First row transition metal atoms. Theor. Chim. Acta, 92:149–181, 1995. 57 Kristine Pierloot, Birgit Dumez, Per-Olof Widmark, and Björn O. Roos. Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions. IV. Medium size basis sets for the atoms $\ce{H}$–$\ce{Kr}$. Theor. Chim. Acta, 90:87–114, 1995. 58 Victor P. Vysotskiy, Jonas Boström, and Valera Veryazov. A new module for constrained multi-fragment geometry optimization in internal coordinates implemented in the MOLCAS package. J. Comput. Chem., 34:2657–2665, 2013. 59 Yubin Wang, Gaohong Zhai, Binbin Suo, Zhengting Gan, and Zhenyi Wen. Hole–particle correspondence in CI calculations. Chem. Phys. Letters, 375:134–140, 2003. 60 Bing Suo, Gaohong Zhai, Yubin Wang, Zhenyi Wen, Xiangqian Hu, and Lemin Li. Parallelization of MRCI based on hole–particle symmetry. J. Comput. Chem., 26:88–96, 2005. 61 János Pipek and Paul G. Mezey. A fast intrinsic localization procedure applicable for ab initio and semiempirical linear combination of atomic orbital wave functions. J. Chem. Phys., 90:4916–4926, 1989. 62 S. F. Boys. Construction of some molecular orbitals to be approximately invariant for changes from one molecule to another. Rev. Mod. Phys., 32:296–299, 1960. 63 J. M. Foster and S. F. Boys. Canonical configurational interaction procedure. Rev. Mod. Phys., 32:300–302, 1960. 64 Clyde Edmiston and Klaus Ruedenberg. Localized atomic and molecular orbitals. Rev. Mod. Phys., 35:457–465, 1963. 65 Francesco Aquilante, Thomas Bondo Pedersen, Alfredo Sánchez de Merás, and Henrik Koch. Fast noniterative orbital localization for large molecules. J. Chem. Phys., 125:174101, 2006. 66 Joseph E. Subotnik, Yihan Shao, WanZhen Liang, and Martin Head-Gordon. An efficient method for calculating maxima of homogeneous functions of orthogonal matrices: Applications to localized occupied orbitals. J. Chem. Phys., 121:9220–9229, 2004. 67 Laura Gagliardi, Roland Lindh, and Gunnar Karlström. Local properties of quantum chemical systems: The LoProp approach. J. Chem. Phys., 121:4494–4500, 2004. 68 Axel D. Becke and Erin R. Johnson. Exchange-hole dipole moment and the dispersion interaction. J. Chem. Phys., 122:154104, 2005. 69 Anders Bernhardsson, Roland Lindh, Jeppe Olsen, and Markus Fülscher. A direct implementation of the second-order derivatives of multiconfigurational SCF energies and an analysis of the preconditioning in the associated response equation. Mol. Phys., 96:617–628, 1999. 70 Jonna Stålring, Anders Bernhardsson, and Roland Lindh. Analytical gradients of a state average MCSCF state and a state average diagnostic. Mol. Phys., 99:103–114, 2001. 71 Jeppe Olsen, Björn O. Roos, Poul Jørgensen, and Hans Jørgen Aa. Jensen. Determinant based configuration interaction algorithms for complete and restricted configuration interaction spaces. J. Chem. Phys., 89:2185–2192, 1988. 72 Giovanni Li Manni, Rebecca K. Carlson, Sijie Luo, Dongxia Ma, Jeppe Olsen, Donald G. Truhlar, and Laura Gagliardi. Multi-configuration pair-density functional theory. J. Chem. Theory Comput., 10:3669–3680, 2014. 73 Rebecca K. Carlson, Giovanni Li Manni, Andrew L. Sonnenberger, Donald G. Truhlar, and Laura Gagliardi. Multiconfiguration pair-density functional theory: Barrier heights and main group and transition metal energetics. J. Chem. Theory Comput., 11:82–90, 2015. 74 Rebecca K. Carlson, Donald G. Truhlar, and Laura Gagliardi. Multiconfiguration pair-density functional theory: A fully translated gradient approximation and its performance for transition metal dimers and the spectroscopy of $\ce{Re2Cl8^{2-}}$. J. Chem. Theory Comput., 11(9):4077, 2015. 75 Philip W. Anderson. New approach to the theory of superexchange interactions. Phys. Rev., 115(1):2–13, Jul 1959. 76 Philip W. Anderson. Theory of magnetic exchange interactions: Exchange in insulators and semiconductors. In Frederick Seitz and David Turnbull, editors, Solid State Physics, volume 14, pages 99–214. Academic Press, 1963. 77 M. E. Lines. Orbital angular momentum in the theory of paramagnetic clusters. J. Chem. Phys., 55(6):2977–2984, 1971. 78 A. Wallqvist, P. Ahlström, and G. Karlström. New intermolecular energy calculation scheme: Applications to potential surface and liquid properties of water. J. Phys. Chem., 94:1649–1656, 1990. 79 Nigel W. Moriarty and Gunnar Karlström. Electronic polarization of a water molecule in water. A combined quantum chemical and statistical mechanical treatment. J. Phys. Chem., 100:17791–17796, 1996. 80 Anders Öhrn and Gunnar Karlström. A theoretical study of the solvent shift to the $n\to\pi^*$ transition in formaldehyde with an effective discrete quantum chemical solvent model including non-electrostatic perturbation. Mol. Phys., 104:3087–3099, 2006. 81 Anders Öhrn and Francesco Aquilante. p-benzoquinone in aqueous solution: Stark shifts in spectra, asymmetry in solvent structure. Phys. Chem. Chem. Phys., 9:470–480, 2007. 82 Anders Öhrn. Development and Application of a First Principle Molecular Model for Solvent Effects. PhD thesis, Lunds Universitet, Theor. Chemistry, Chem. Center, P.O.B. 124,S-221 00 Lund, Sweden, 2008. 83 Per-Åke Malmqvist, Alistair Rendell, and Björn O. Roos. The restricted active space self-consistent-field method, implemented with a split graph unitary group approach. J. Phys. Chem., 94:5477–5482, 1990. 84 Björn O. Roos, Peter R. Taylor, and Per E. M. Siegbahn. A complete active space SCF method (CASSCF) using a density matrix formulated super-CI approach. Chem. Phys., 48:157–173, 1980. 85 Björn O. Roos. The complete active space self-consistent field method and its applications in electronic structure calculations. In K. P. Lawley, editor, Ab Initio Methods in Quantum Chemistry Part II, volume 69 of Advances in Chemical Physics, pages 399–445. John Wiley & Sons, Hoboken, NJ, USA, 1987. 86 Björn O. Roos. The complete active space SCF method in a Fock-matrix-based super-CI formulation. Int. J. Quantum Chem., 18-S14:175–189, 1980. 87 Francesco Aquilante, Thomas Bondo Pedersen, and Roland Lindh. Low-cost evaluation of the exchange Fock matrix from Cholesky and density fitting representations of the electron repulsion integrals. J. Chem. Phys., 126:194106, 2007. 88 Per-Åke Malmqvist. Calculation of transition density matrices by nonunitary orbital transformations. Int. J. Quantum Chem., 30:479–494, 1986. 89 Per-Åke Malmqvist and Björn O. Roos. The CASSCF state interaction method. Chem. Phys. Letters, 155:189–194, 1989. 90 Steven Vancoillie, Per-Åke Malmqvist, and Kristine Pierloot. Calculation of EPR g tensors for transition-metal complexes based on multiconfigurational perturbation theory (CASPT2). ChemPhysChem, 8:1803–1815, 2007. 91 Steven Vancoillie, Lubomír Rulíšek, Frank Neese, and Kristine Pierloot. Theoretical description of the structure and magnetic properties of nitroxide–Cu(II)–nitroxide spin triads by means of multiconfigurational ab initio calculations. J. Phys. Chem. A, 113:6149–6157, 2009. 92 Chad E. Hoyer, Xuefei Xu, Dongxia Ma, Laura Gagliardi, and Donald G. Truhlar. Diabatization based on the dipole and quadrupole: The DQ method. J. Chem. Phys., 141(11):114104, 2014. 93 Joseph E. Subotnik, Sina Yeganeh, Robert J. Cave, and Mark A. Ratner. Constructing diabatic states from adiabatic states: extending generalized Mulliken–Hush to multiple charge centers with Boys localization. J. Chem. Phys., 129(24):244101, 2008. 94 J. Almlöf, K. Faegri, Jr., and K. Korsell. Principles for a direct SCF approach to LICAO–MO ab-initio calculations. J. Comput. Chem., 3:385–399, 1982. 95 Dieter Cremer and Jürgen Gauss. An unconventional SCF method for calculations on large molecules. J. Comput. Chem., 7:274–282, 1986. 96 Marco Häser and Reinhart Ahlrichs. Improvements on the direct SCF method. J. Comput. Chem., 10:104–111, 1989. 97 Gunnar Karlström. Dynamical damping based on energy minimization for use ab initio molecular orbital SCF calculations. Chem. Phys. Letters, 67:348–350, 1979. 98 Harrell Sellers. The C2-DIIS convergence acceleration algorithm. Int. J. Quantum Chem., 45:31–41, 1993. 99 Thomas H. Fischer and Jan Almlöf. General methods for geometry and wave function optimization. J. Phys. Chem., 96:9768–9774, 1992. 100 S. H. Vosko, L. Wilk, and M. Nusair. Accurate spin-dependent electron liquid correlation energies for local spin density calculations: A critical analysis. Can. J. Phys., 58:1200–1211, 1980. 101 A. D. Becke. Density-functional exchange-energy approximation with correct asymptotic behavior. Phys. Rev. A, 38:3098–3100, 1988. 102 P. Hohenberg and W. Kohn. Inhomogeneous electron gas. Phys. Rev., 136:B864–B871, 1964. 103 W. Kohn and L. J. Sham. Self-consistent equations including exchange and correlation effects. Phys. Rev., 140:A1133–A1138, 1965. 104 J. C. Slater. Quantum Theory of Molecular and Solids. Vol. 4. The Self-Consistent Field for Molecular and Solids. McGraw–Hill, New York, NY, USA, 1974. 105 A. D. Becke. Density functional calculations of molecular bond energies. J. Chem. Phys., 84:4524–4529, 1986. 106 Axel D. Becke and Erin R. Johnson. A unified density-functional treatment of dynamical, nondynamical, and dispersion correlations. J. Chem. Phys., 127:124108, 2007. 107 Nicholas C. Handy and Aron J. Cohen. Left–right correlation energy. Mol. Phys., 99:403–412, 2001. 108 Chengteh Lee, Weitao Yang, and Robert G. Parr. Development of the Colle–Salvetti correlation-energy formula into a functional of the electron density. Phys. Rev. B, 37:785–789, 1988. 109 Burkhard Miehlich, Andreas Savin, Hermann Stoll, and Heinzwerner Preuss. Results obtained with the correlation energy density functionals of Becke and Lee, Yang and Parr. Chem. Phys. Letters, 157:200–206, 1989. 110 John P. Perdew, Kieron Burke, and Matthias Ernzerhof. Generalized gradient approximation made simple. Phys. Rev. Letters, 77:3865–3868, 1996. 111 Axel D. Becke. Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys., 98:5648–5652, 1993. 112 Stefan Grimme. Semiempirical hybrid density functional with perturbative second-order correlation. J. Chem. Phys., 124:034108, 2006. 113 Phillip A. Stewart and Peter M. W. Gill. Becke–Wigner: A simple but powerful density functional. J. Chem. Soc. Faraday Trans., 91:4337–4341, 1995. 114 Peter M. W. Gill. A new gradient-corrected exchange functional. Mol. Phys., 89:433–445, 1996. 115 Wee-Meng Hoe, Aaron J. Cohen, and Nicholas C. Handy. Assessment of a new local exchange functional OPTX. Chem. Phys. Letters, 341:319–328, 2001. 116 Mark J. Allen, Thomas W. Keal, and David J. Tozer. Improved NMR chemical shifts in density functional theory. Chem. Phys. Letters, 380:70–77, 2003. 117 Thomas W. Keal and David J. Tozer. A semiempirical generalized gradient approximation exchange-correlation functional. J. Chem. Phys., 121:5654–5660, 2004. 118 John P. Perdew, Matthias Ernzerhof, and Kieron Burke. Rationale for mixing exact exchange with density functional approximations. J. Chem. Phys., 105:9982–9985, 1996. 119 Adrienn Ruzsinszky, Gábor I. Csonka, and Gustavo E. Scuseria. Regularized gradient expansion for atoms, molecules, and solids. J. Chem. Theory Comput., 5:763–769, 2009. 120 Vincent Tognetti, Pietro Cortona, and Carlo Adamo. A new parameter-free correlation functional based on an average atomic reduced density gradient analysis. J. Chem. Phys., 128:034101, 2008. 121 Marcel Swart, Miquel Solà, and F. Matthias Bickelhaupt. A new all-round density functional based on spin states and SN2 barriers. J. Chem. Phys., 131:049103, 2009. 122 Yan Zhao and Donald G. Truhlar. A new local density functional for main-group thermochemistry, transition metal bonding, thermochemical kinetics, and noncovalent interactions. J. Chem. Phys., 125:194101, 2006. 123 Yan Zhao and Donald G. Truhlar. Density functional for spectroscopy: No long-range self-interaction error, good performance for Rydberg and charge-transfer states, and better performance on average than B3LYP for ground states. J. Phys. Chem. A, 110:13126–13130, 2006. 124 Yan Zhao and Donald G. Truhlar. The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: Two new functionals and systematic testing of four M06-class functionals and 12 other functionals. Theor. Chem. Acc., 120:215–241, 2008. 125 Yan Zhao and Donald G. Truhlar. Density functionals with broad applicability in chemistry. Acc. Chem. Res., 41:157–167, 2008. 126 R. Lindh, U. Ryu, and B. Liu. The reduced multiplication scheme of the Rys quadrature and new recurrence relations for auxiliary function based two-electron integral evaluation. J. Chem. Phys., 95:5889–5897, 1991. 127 Ernest R. Davidson. Use of double cosets in constructing integrals over symmetry orbitals. J. Chem. Phys., 62:400–403, 1975. 128 Benny G. Johnson, Peter M. W. Gill, and John A. Pople. The performance of a family of density functional methods. J. Chem. Phys., 98:5612–5626, 1993. 129 Nicholas C. Handy, David J. Tozer, Gregory J. Laming, Christopher W. Murray, and Roger D. Amos. Analytic second derivatives of the potential energy surface. Isr. J. Chem., 33:331–344, 1993. 130 Jon Baker, Jan Andzelm, Andrew Scheiner, and Bernard Delley. The effect of grid quality and weight derivatives in density functional calculations. J. Chem. Phys., 101:8894–8902, 1994. 131 Michael E. Mura and Peter J. Knowles. Improved radial grids for quadrature in molecular density-functional calculations. J. Chem. Phys., 104:9848–9858, 1996. 132 A. D. Becke. A multicenter numerical integration scheme for polyatomic molecules. J. Chem. Phys., 88:2547–2553, 1988. 133 Christopher W. Murray, Nicholas C. Handy, and Gregory J. Laming. Quadrature schemes for integrals of density functional theory. Mol. Phys., 78:997–1014, 1993. 134 Oliver Treutler and Reinhart Ahlrichs. Efficient molecular numerical integration schemes. J. Chem. Phys., 102:346–354, 1995. 135 Roland Lindh, Per-Åke Malmqvist, and Laura Gagliardi. Molecular integrals by numerical quadrature. I. Radial integration. Theor. Chem. Acc., 106:178–187, 2001. 136 Daoling Peng and Markus Reiher. Exact decoupling of the relativistic Fock operator. Theor. Chem. Acc., 131:1081, 2012. 137 Daoling Peng and Kimihiko Hirao. An arbitrary order Douglas–Kroll method with polynomial cost. J. Chem. Phys., 130:044102, 2009. 138 Markus Reiher and Alexander Wolf. Exact decoupling of the Dirac Hamiltonian. I. General theory. J. Chem. Phys., 121:2037–2047, 2004. 139 Markus Reiher and Alexander Wolf. Exact decoupling of the Dirac Hamiltonian. II. The generalized Douglas–Kroll–Hess transformation up to arbitrary order. J. Chem. Phys., 121:10945–10956, 2004. 140 Markus Reiher. Douglas–Kroll–Hess theory: a relativistic electrons-only theory for chemistry. Theor. Chem. Acc., 116:241–252, 2006. 141 Alexander Wolf, Markus Reiher, and Bernd Artur Hess. The generalized Douglas–Kroll transformation. J. Chem. Phys., 117:9215–9226, 2002. 142 Alexander Wolf and Markus Reiher. Exact decoupling of the Dirac Hamiltonian. III. Molecular properties. J. Chem. Phys., 124:064102, 2006. 143 Alexander Wolf and Markus Reiher. Exact decoupling of the Dirac Hamiltonian. IV. Automated evaluation of molecular properties within the Douglas–Kroll–Hess theory up to arbitrary order. J. Chem. Phys., 124:064103, 2006. 144 Werner Kutzelnigg and Wenjian Liu. Quasirelativistic theory equivalent to fully relativistic theory. J. Chem. Phys., 123:241102, 2005. 145 Wenjian Liu and Daoling Peng. Infinite-order quasirelativistic density functional method based on the exact matrix quasirelativistic theory. J. Chem. Phys., 125:044102, 2006. 146 Daoling Peng, Wenjian Liu, Yunlong Xiao, and Lan Cheng. Making four- and two-component relativistic density functional methods fully equivalent based on the idea of "from atoms to molecule". J. Chem. Phys., 127:104106, 2007. 147 Maria Barysz, Andrzej J. Sadlej, and Jaap G. Snijders. Nonsingular two/one-component relativistic Hamiltonians accurate through arbitrary high order in $\alpha^2$. Int. J. Quantum Chem., 65:225–239, 1997. 148 Dariusz Kędziera and Maria Barysz. Non-iterative approach to the infinite-order two-component (IOTC) relativistic theory and the non-symmetric algebraic Riccati equation. Chem. Phys. Letters, 446:176–181, 2007. 149 Daoling Peng and Markus Reiher. Local relativistic exact decoupling. J. Chem. Phys., 136:244108, 2012. 150 Liviu F. Chibotaru, Liviu Ungur, and Alessandro Soncini. The origin of nonmagnetic Kramers doublets in the ground state of dysprosium triangles: Evidence for a toroidal magnetic moment. Angew. Chem. Int. Ed., 47:4126–4129, 2008. 151 Liviu F. Chibotaru, Liviu Ungur, Christophe Aronica, Hani Elmoll, Guillaume Pillet, and Dominique Luneau. Structure, magnetism, and theoretical study of a mixed-valence $\ce{Co^{II}_3Co^{III}_4}$ heptanuclear wheel: Lack of SMM behavior despite negative magnetic anisotropy. J. Am. Chem. Soc., 130:12445–12455, 2008. 152 Liviu F. Chibotaru and Liviu Ungur. Ab initio calculation of anisotropic magnetic properties of complexes. I. Unique definition of pseudospin Hamiltonians and their derivation. J. Chem. Phys., 137:064112, 2012. 153 Liviu Ungur and Liviu F. Chibotaru. Ab initio crystal field for lanthanides. Chem. Eur. J., 23(15):3708–3718, 2017. 154 Czeslaw Rudowicz. Transformation relations for the conventional okq and normalised o'kq Stevens Operator Equivalents with k=1 to 6 and $-k \le q \le k$. J. Phys. C: Solid State Phys., 18(7):1415, 1985. 155 C. Rudowicz and C. Y. Chung. Generalization of the extended Stevens operators to higher ranks and spins and systematic review of the tables of the tensor operators and their matrix elements. J. Phys.: Condens. Matter, 16(32):5825, 2004. 156 Czeslaw Rudowicz and Miroslav Karbowiak. Disentangling intricate web of interrelated notions at the interface between the physical (crystal field) Hamiltonians and the effective (spin) Hamiltonians. Coord. Chem. Rev., 287:28, 2015. 157 Roland Lindh, Anders Bernhardsson, Gunnar Karlström, and Per-Åke Malmqvist. On the use of a Hessian model function in molecular geometry optimizations. Chem. Phys. Letters, 241:423–428, 1995. 158 Chunyang Peng, Philippe Y. Ayala, H. Bernhard Schlegel, and Michael J. Frisch. Using redundant internal coordinates to optimize equilibrium geometries and transition states. J. Comput. Chem., 17:49–56, 1996. 159 P. Pulay and G. Fogarasi. Geometry optimization in redundant internal coordinates. J. Chem. Phys., 96:2856–2860, 1992. 160 Jon Baker, Alain Kessi, and Bernard Delley. The generation and use of delocalized internal coordinates in geometry optimization. J. Chem. Phys., 105:192–212, 1996. 161 Roland Lindh, Anders Bernhardsson, and Martin Schütz. Force-constant weighted redundant coordinates in molecular geometry optimizations. Chem. Phys. Letters, 303:567–575, 1999. 162 Jon Baker. Techniques for geometry optimization: A comparison of Cartesian and natural internal coordinates. J. Comput. Chem., 14:1085–1100, 1993. 163 M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. A. Keith, G. A. Petersson, J. A. Montgomery, Jr., K. Raghavachari, M. A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, J. Cioslowski, B. B. Stefanov, A. Nanayakkara, M. Challacombe, C. Y. Peng, P. Y. Ayala, W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez, and J. A. Pople. Gaussian 94 (Revision A.1). Gaussian, Inc., Pittsburgh, PA, USA, 1995. 164 Josep Maria Bofill. Updated Hessian matrix and the restricted step method for locating transition structures. J. Comput. Chem., 15:1–11, 1994. 165 Josep Maria Bofill. Remarks on the updated Hessian matrix methods. Int. J. Quantum Chem., 94:324–332, 2003. 166 Ajit Banerjee, Noah Adams, Jack Simons, and Ron Shepard. Search for stationary points on surfaces. J. Phys. Chem., 89:52–57, 1985. 167 Emili Besalú and Josep Maria Bofill. On the automatic restricted-step rational-function-optimization method. Theor. Chem. Acc., 100:265–274, 1998. 168 Pál Császár and Péter Pulay. Geometry optimization by direct inversion in the iterative subspace. J. Mol. Struct., 114:31–34, 1984. 169 Péter Pulay. Convergence acceleration of iterative sequences. The case of SCF iteration. Chem. Phys. Letters, 73:393–398, 1980. 170 P. Pulay. Improved SCF convergence acceleration. J. Comput. Chem., 3:556–560, 1982. 171 Charles J. Cerjan and William H. Miller. On finding transition states. J. Chem. Phys., 75:2800–2806, 1981. 172 Satoshi Maeda, Koichi Ohno, and Keiji Morokuma. Updated branching plane for finding conical intersections without coupling derivative vectors. J. Chem. Theory Comput., 6(5):1538–1545, 2010. 173 John C. Tully. Molecular dynamics with electronic transitions. J. Chem. Phys., 93(2):1061–1071, 1990. 174 Sharon Hammes-Schiffer and John C. Tully. Proton transfer in solution: Molecular dynamics with quantum transitions. J. Chem. Phys., 101(6):4657–4667, 1994. 175 Giovanni Granucci and Maurizio Persico. Critical appraisal of the fewest switches algorithm for surface hopping. J. Chem. Phys., 126(13):134114, 2007. 176 F. Plasser, M. Wormit, S. A. Mewes, B. Thomitzni, and A. Dreuw. libwfa: Wave-function analysis tool library for quantum chemical applications. 177 Felix Plasser, Stefanie A. Mewes, Andreas Dreuw, and Leticia González. Detailed wave function analysis for multireference methods: Implementation in the Molcas program package and applications to tetracene. J. Chem. Theory Comput., 13(11):5343–5353, 2017. 178 Richard L. Martin. Natural transition orbitals. J. Chem. Phys., 118(11):4775–4777, 2003. 179 Felix Plasser, Michael Wormit, and Andreas Dreuw. New tools for the systematic analysis and visualization of electronic excitations. I. Formalism. J. Chem. Phys., 141(2):024106, 2014. 180 Felix Plasser, Stefanie A. Bäppler, Michael Wormit, and Andreas Dreuw. New tools for the systematic analysis and visualization of electronic excitations. II. Applications. J. Chem. Phys., 141(2):024107, 2014. 181 Stefanie A. Bäppler, Felix Plasser, Michael Wormit, and Andreas Dreuw. Exciton analysis of many-body wave functions: Bridging the gap between the quasiparticle and molecular orbital pictures. Phys. Rev. A, 90(5):052521, 2014. 182 Felix Plasser, Benjamin Thomitzni, Stefanie A. Bäppler, Jan Wenzel, Dirk R. Rehn, Michael Wormit, and Andreas Dreuw. Statistical analysis of electronic excitation processes: Spatial location, compactness, charge transfer, and electron-hole correlation. J. Comput. Chem., 36(21):1609–1620, 2015. 183 Felix Plasser and Hans Lischka. Analysis of excitonic and charge transfer interactions from quantum chemical calculations. J. Chem. Theory Comput., 8(8):2777–2789, 2012. 184 F. Plasser. TheoDORE: a package for theoretical density, orbital relaxation, and exciton analysis. 185 Martin Head-Gordon. Characterizing unpaired electrons from the one-particle density matrix. Chem. Phys. Letters, 372(3-4):508–511, 2003. 186 Felix Plasser. Entanglement entropy of electronic excitations. J. Chem. Phys., 144(19):194107, 2016. 187 Andrzej J. Sadlej. Medium-size polarized basis sets for high-level correlated calculations of molecular electric properties. Collect. Czech. Chem. Commun., 53:1995–2016, 1988. 188 Andrzej J. Sadlej. Medium-size polarized basis sets for high-level-correlated calculations of molecular electric properties. II. Second-row atoms: $\ce{Si}$ through $\ce{Cl}$. Theor. Chim. Acta, 79:123–140, 1991. 189 Andrzej J. Sadlej and Miroslav Urban. Medium-size polarized basis sets for high-level-correlated calculations of molecular electric properties: III. Alkali ($\ce{Li}$, $\ce{Na}$, $\ce{K}$, $\ce{Rb}$) and alkaline-earth ($\ce{Be}$, $\ce{Mg}$, $\ce{Ca}$, $\ce{Sr}$) atoms. J. Mol. Struct. Theochem, 234:147–171, 1991. 190 Andrzej J. Sadlej. Medium-size polarized basis sets for high-level-correlated calculations of molecular electric properties. IV. Third-row atoms: $\ce{Ge}$ through $\ce{Br}$. Theor. Chim. Acta, 81:45–63, 1991. 191 Andrzej J. Sadlej. Medium-size polarized basis sets for high-level-correlated calculations of molecular electric properties. V. Fourth-row atoms: $\ce{Sn}$ through $\ce{I}$. Theor. Chim. Acta, 81:339–354, 1992. 192 Vladimir Kellö and Andrzej J. Sadlej. Estimates of relativistic contributions to molecular properties. J. Chem. Phys., 93:8122–8132, 1990. 193 Andrzej J. Sadlej and Miroslav Urban. Mutual dependence of relativistic and electron correlation contributions to molecular properties: The dipole moment of $\ce{AgH}$. Chem. Phys. Letters, 176:293–302, 1991. 194 Sigeru Huzinaga, Luis Seijo, Zoila Barandiarán, and Mariusz Klobukowski. The ab initio model potential method. Main group elements. J. Chem. Phys., 86:2132–2145, 1987. 195 Zoila Barandiarán and Luis Seijo. The ab initio model potential representation of the crystalline environment. Theoretical study of the local distortion on $\ce{NaCl{:}Cu^+}$. J. Chem. Phys., 89:5739–5746, 1988. 196 Zoila Barandiarán, Luis Seijo, and Sigeru Huzinaga. The ab initio model potential method. Second series transition metal elements. J. Chem. Phys., 93:5843–5850, 1990. 197 Christina Wittborn and Ulf Wahlgren. New relativistic effective core potentials for heavy elements. Chem. Phys., 201:357–362, 1995. 198 Frank Rakowitz, Christel M. Marian, Luis Seijo, and Ulf Wahlgren. Spin-free relativistic no-pair ab initio core model potentials and valence basis sets for the transition metal elements $\ce{Sc}$ to $\ce{Hg}$. Part I. J. Chem. Phys., 110:3678–3686, 1999. 199 Frank Rakowitz, Christel M. Marian, and Luis Seijo. Spin-free relativistic no-pair ab initio core model potentials and valence basis sets for the transition metal elements $\ce{Sc}$ to $\ce{Hg}$. II. J. Chem. Phys., 111:10436–10443, 1999. 200 Z. Barandiarán and L. Seijo. Local properties of imperfect crystals. In S. Fraga, editor, Computational Chemistry: Structure, Interactions and Reactivity, volume 77B of Studies in Physical and Theoretical Chemistry, pages 435–461. Elsevier, Amsterdam, Netherlands, 1992. 201 James C. Phillips and Leonard Kleinman. New method for calculating wave functions in crystals and molecules. Phys. Rev., 116:287–294, 1959. 202 S. Huzinaga and A. A. Cantu. Theory of separability of many-electron systems. J. Chem. Phys., 55:5543–5549, 1971. 203 Sigeru Huzinaga, Dennis McWilliams, and Antonio A. Cantu. Projection operators in Hartree–Fock theory. Adv. Quantum Chem., 7:187–220, 1973. 204 José Luis Pascual, Luis Seijo, and Zoila Barandiarán. Ab initio model potential study of environmental effects on the Jahn–Teller parameters of $\ce{Cu^{2+}}$ and $\ce{Ag^{2+}}$ impurities in $\ce{MgO}$, $\ce{CaO}$, and $\ce{SrO}$ hosts. J. Chem. Phys., 98:9715–9724, 1993. 205 M. Pelissier, N. Komiha, and J.-P. Daudey. One-center expansion for pseudopotential matrix elements. J. Comput. Chem., 9:298–302, 1988. 206 P. Jeffrey Hay and Willard R. Wadt. Ab initio effective core potentials for molecular calculations. Potentials for the transition metal atoms $\ce{Sc}$ to $\ce{Hg}$. J. Chem. Phys., 82:270–283, 1985. 207 P. Jeffrey Hay and Willard R. Wadt. Ab initio effective core potentials for molecular calculations. Potentials for main group elements $\ce{Na}$ to $\ce{Bi}$. J. Chem. Phys., 82:284–298, 1985. 208 P. Jeffrey Hay and Willard R. Wadt. Ab initio effective core potentials for molecular calculations. Potentials for $\ce{K}$ to $\ce{Au}$ including the outermost core orbitals. J. Chem. Phys., 82:299–310, 1985. 209 Patricio Fuentealba, Heinzwerner Preuss, Hermann Stoll, and László Von Szentpály. A proper account of core-polarization with pseudopotentials: Single valence-electron alkali compounds. Chem. Phys. Letters, 89:418–422, 1982. 210 P. Fuentealba, L. von Szentpály, H. Preuss, and H. Stoll. Pseudopotential calculations for alkaline-earth atoms. J. Phys. B: At. Mol. Phys., 18:1287–1296, 1985. 211 G. Igel-Mann, H. Stoll, and H. Preuss. Pseudopotentials for main group elements (IIIa through VIIa). Mol. Phys., 65:1321–1328, 1988. 212 Andreas Bergner, Michael Dolg, Wolfgang Küchle, Hermann Stoll, and Heinzwerner Preuß. Ab initio energy-adjusted pseudopotentials for elements of groups 13–17. Mol. Phys., 80:1431–1441, 1993. 213 P. Fuentealba, H. Stoll, L. von Szentpály, P. Schwerdtfeger, and H. Preuss. On the reliability of semi-empirical pseudopotentials: Simulation of Hartree–Fock and Dirac–Fock results. J. Phys. B: At. Mol. Phys., 16:L323–L328, 1983. 214 M. Kaupp, P. v. R. Schleyer, H. Stoll, and H. Preuss. Pseudopotential approaches to $\ce{Ca}$, $\ce{Sr}$, and $\ce{Ba}$ hydrides. Why are some alkaline earth $\ce{MX2}$ compounds bent? J. Chem. Phys., 94:1360–1366, 1991. 215 M. Dolg, U. Wedig, H. Stoll, and H. Preuss. Energy-adjusted ab initio pseudopotentials for the first row transition elements. J. Chem. Phys., 86:866–872, 1987. 216 Ulrich Wedig, Michael Dolg, Hermann Stoll, and Heinzwerner Preuss. Energy-adjusted pseudopotentials for transition-metal elements. In A. Veillard, editor, Quantum Chemistry: The Challenge of Transition Metals and Coordination Chemistry, volume 176 of NATO ASI Series, pages 79–89. D. Reidel, Dordrecht, Netherlands, 1986. 217 László Von Szentpály, Patricio Fuentealba, Heinzwerner Preuss, and Hermann Stoll. Pseudopotential calculations on $\ce{Rb2^+}$, $\ce{Cs2^+}$, $\ce{RbH^+}$, $\ce{CsH^+}$ and the mixed alkali dimer ions. Chem. Phys. Letters, 93:555–559, 1982. 218 D. Andrae, U. Häußermann, M. Dolg, H. Stoll, and H. Preuß. Energy-adjusted ab initio pseudopotentials for the second and third row transition elements. Theor. Chim. Acta, 77:123–141, 1990. 219 H. Stoll, P. Fuentealba, P. Schwerdtfeger, J. Flad, L. v. Szentpály, and H. Preuss. $\ce{Cu}$ and $\ce{Ag}$ as one-valence-electron atoms: CI results and quadrupole corrections for $\ce{Cu2}$, $\ce{Ag2}$, $\ce{CuH}$, and $\ce{AgH}$. J. Chem. Phys., 81:2732–2736, 1984. 220 W. Küchle, M. Dolg, H. Stoll, and H. Preuss. Ab initio pseudopotentials for $\ce{Hg}$ through $\ce{Rn}$. I. Parameter sets and atomic calculations. Mol. Phys., 74:1245–1263, 1991. 221 Gudrun Igel-Mann. Semiempirische Pseudopotentiale; Untersuchungen an Hauptgruppenelementen und Nebengruppenelementen mit abgeschlossener d-Schale. PhD thesis, Universität Stuttgart, Institut für Theoretische Chemie, 1987. 222 M. Dolg, H. Stoll, and H. Preuss. A combination of quasirelativistic pseudopotential and ligand field calculations for lanthanoid compounds. Theor. Chim. Acta, 85:441–450, 1993. 223 M. Dolg, H. Stoll, and H. Preuss. Energy-adjusted ab initio pseudopotentials for the rare earth elements. J. Chem. Phys., 90:1730–1734, 1989. 224 Michael Dolg, Peter Fulde, Wolfgang Küchle, Carl-Stefan Neumann, and Hermann Stoll. Ground state calculations of di-${\pi}$-cyclooctatetraene cerium. J. Chem. Phys., 94:3011–3017, 1991. 225 M. Dolg, H. Stoll, A. Savin, and H. Preuss. Energy-adjusted pseudopotentials for the rare earth elements. Theor. Chim. Acta, 75:173–194, 1989. 226 Michael Dolg, Hermann Stoll, Heinz-Jürgen Flad, and Heinzwerner Preuss. Ab initio pseudopotential study of $\ce{Yb}$ and $\ce{YbO}$. J. Chem. Phys., 97:1162–1173, 1992. 227 Michael Dolg, Hermann Stoll, Heinzwerner Preuss, and Russell M. Pitzer. Relativistic and correlation effects for element 105 (hahnium, $\ce{Ha}$): A comparative study of $\ce{M}$ and $\ce{MO}$ ($\ce{M}$ = $\ce{Nb}$, $\ce{Ta}$, $\ce{Ha}$) using energy-adjusted ab initio pseudopotentials. J. Phys. Chem., 97:5852–5859, 1993. 228 Peter Schwerdtfeger, Michael Dolg, W. H. Eugen Schwarz, Graham A. Bowmaker, and Peter D. W. Boyd. Relativistic effects in gold chemistry. I. Diatomic gold compounds. J. Chem. Phys., 91:1762–1774, 1989. 229 U. Häussermann, M. Dolg, H. Stoll, H. Preuss, P. Schwerdtfeger, and R. M. Pitzer. Accuracy of energy-adjusted quasirelativistic ab initio pseudopotentials. All-electron and pseudopotential benchmark calculations for $\ce{Hg}$, $\ce{HgH}$ and their cations. Mol. Phys., 78:1211–1224, 1993. 230 W. Küchle, M. Dolg, H. Stoll, and H. Preuss. Energy-adjusted pseudopotentials for the actinides. Parameter sets and test calculations for thorium and thorium monoxide. J. Chem. Phys., 100:7535–7542, 1994. 231 Andreas Nicklass, Michael Dolg, Hermann Stoll, and Heinzwerner Preuss. Ab initio energy-adjusted pseudopotentials for the noble gases $\ce{Ne}$ through $\ce{Xe}$: Calculation of atomic dipole and quadrupole polarizabilities. J. Chem. Phys., 102:8942–8952, 1995. 232 Thierry Leininger, Andreas Nicklass, Hermann Stoll, Michael Dolg, and Peter Schwerdtfeger. The accuracy of the pseudopotential approximation. II. A comparison of various core sizes for indium pseudopotentials in calculations for spectroscopic constants of $\ce{InH}$, $\ce{InF}$, and $\ce{InCl}$. J. Chem. Phys., 105:1052–1059, 1996. 233 Xiaoyan Cao, Michael Dolg, and Hermann Stoll. Valence basis sets for relativistic energy-consistent small-core actinide pseudopotentials. J. Chem. Phys., 118:487–496, 2003. 234 L. R. Kahn and W. A. Goddard, III. A direct test of the validity of the use of pseudopotentials in molecules. Chem. Phys. Letters, 2:667–670, 1968. 235 Phillip A. Christiansen, Yoon S. Lee, and Kenneth S. Pitzer. Improved ab initio effective core potentials for molecular calculations. J. Chem. Phys., 71:4445–4450, 1979. 236 Philippe Durand and Jean-Claude Barthelat. A theoretical method to determine atomic pseudopotentials for electronic structure calculations of molecules and solids. Theor. Chim. Acta, 38:283–302, 1975. 237 Chris-Kriton Skylaris, Laura Gagliardi, Nicholas C. Handy, Andrew G. Ioannou, Steven Spencer, Andrew Willetts, and Adrian M. Simper. An efficient method for calculating effective core potential integrals which involve projection operators. Chem. Phys. Letters, 296:445–451, 1998. 238 Harry Partridge, Stephen R. Langhoff, and Charles W. Bauschlicher, Jr. Electronic spectroscopy of diatomic molecules. In Stephen R. Langhoff, editor, Quantum Mechanical Electronic Structure Calculations with Chemical Accuracy, volume 13 of Understanding Chemical Reactivity, pages 209–260. Kluwer Academic Publishers, Dordrecht, Netherlands, 1995. 239 Peter R. Taylor. Molecular symmetry and quantum chemistry. In Björn O. Roos, editor, Lecture Notes in Quantum Chemistry. European Summer School in Quantum Chemistry, volume 58 of Lecture Notes in Chemistry, pages 89–176. Springer-Verlag, Berlin, Germany, 1992. 240 Margareta R. A. Blomberg, Per E. M. Siegbahn, and Björn O. Roos. A theoretical study of $\ce{NiH}$ optical spectrum and potential curves. Mol. Phys., 47:127–143, 1982. 241 Rosendo Pou-Amérigo, Manuela Merchán, Ignacio Nebot-Gil, Per-Åke Malmqvist, and Björn O. Roos. The chemical bonds in $\ce{CuH}$, $\ce{Cu2}$, $\ce{NiH}$, and $\ce{Ni2}$ studied with multiconfigurational second order perturbation theory. J. Chem. Phys., 101:4893–4902, 1994. 242 Kerstin Andersson and Björn O. Roos. Excitation energies in the nickel atom studied with the complete active space SCF method and second-order perturbation theory. Chem. Phys. Letters, 191:507–514, 1992. 243 Gerhard Herzberg. Molecular Spectra and Molecular Structure. Vol I. Spectra of Diatomic Molecules. D. Van Nostrand, Princeton, NJ, USA, 2nd edition, 1966. 244 Peter R. Taylor. Accurate calculations and calibration. In Björn O. Roos, editor, Lecture Notes in Quantum Chemistry. European Summer School in Quantum Chemistry, volume 58 of Lecture Notes in Chemistry, pages 325–412. Springer-Verlag, Berlin, Germany, 1992. 245 Remedios González-Luque, Manuela Merchán, and Björn O. Roos. A theoretical determination of the dissociation energy of the nitric oxide dimer. Theor. Chim. Acta, 88:425–435, 1994. 246 M. Perić, B. Engels, and S. D. Peyerimhoff. Theoretical spectroscopy on small molecules: Ab initio investigations of vibronic structure, spin–orbit splittings and magnetic hyperfine effects in the electronic spectra of triatomic molecules. In Stephen R. Langhoff, editor, Quantum Mechanical Electronic Structure Calculations with Chemical Accuracy, volume 13 of Understanding Chemical Reactivity, pages 261–356. Kluwer Academic Publishers, Dordrecht, Netherlands, 1995. 247 Trygve Helgaker. Optimization of minima and saddle points. In Björn O. Roos, editor, Lecture Notes in Quantum Chemistry. European Summer School in Quantum Chemistry, volume 58 of Lecture Notes in Chemistry, pages 295–324. Springer-Verlag, Berlin, Germany, 1992. 248 Mercedes Rubio, Manuela Merchán, Enrique Ortí, and Björn O. Roos. A theoretical study of the electronic spectrum of naphthalene. Chem. Phys., 179:395–409, 1994. 249 Luis Serrano-Andrés, Manuela Merchán, Ignacio Nebot-Gil, Roland Lindh, and Björn O. Roos. Towards an accurate molecular orbital theory for excited states: Ethene, butadiene, and hexatriene. J. Chem. Phys., 98:3151–3162, 1993. 250 Luis Serrano-Andrés and Björn O. Roos. Theoretical study of the absorption and emission spectra of indole in the gas phase and in a solvent. J. Am. Chem. Soc., 118:185–195, 1996. 251 Christopher S. Page, Manuela Merchán, Luis Serrano-Andrés, and Massimo Olivucci. A theoretical study of the low-lying excited states of trans- and cis-urocanic acid. J. Phys. Chem. A, 103:9864–9871, 1999. 252 Rosendo Pou-Amérigo, Manuela Merchán, and Enrique Ortí. Theoretical study of the electronic spectrum of p-benzoquinone. J. Chem. Phys., 110:9536–9546, 1999. 253 C. E. Blom and A. Bauder. Microwave spectrum, rotational constants and dipole moment of s-cis acrolein. Chem. Phys. Letters, 88:55–58, 1982. 254 Vicent Molina and Manuela Merchán. Theoretical analysis of the electronic spectra of benzaldehyde. J. Phys. Chem. A, 105:3745–3751, 2001. 255 Francis Ford, Tetsuro Yuzawa, Matthew S. Platz, Stephan Matzinger, and Markus Fülscher. Rearrangement of dimethylcarbene to propene: Study by laser flash photolysis and ab Initio molecular orbital theory. J. Am. Chem. Soc., 120:4430–4438, 1998. 256 Timothy J. Lee and Peter R. Taylor. A diagnostic for determining the quality of single-reference electron correlation methods. Int. J. Quantum Chem., 36-S23:199–207, 1989. 257 Timothy J. Lee and Gustavo E. Scuseria. Achieving chemical accuracy with coupled-cluster theory. In Stephen R. Langhoff, editor, Quantum Mechanical Electronic Structure Calculations with Chemical Accuracy, volume 13 of Understanding Chemical Reactivity, pages 47–108. Kluwer Academic Publishers, Dordrecht, Netherlands, 1995. 258 S. Matzinger and M. P. Fülscher. Methyl substitution in carbenes. A theoretical prediction of the singlet–triplet energy separation of dimethylcarbene. J. Phys. Chem., 99:10747–10751, 1995. 259 David J. Tozer, Roger D. Amos, Nicholas C. Handy, Björn O. Roos, and Luis Serrano-Andrés. Does density functional theory contribute to the understanding of excited states of unsaturated organic compounds? Mol. Phys., 97:859–868, 1999. 260 Luis Serrano-Andrés, Markus P. Fülscher, Björn O. Roos, and Manuela Merchán. Theoretical study of the electronic spectrum of imidazole. J. Phys. Chem., 100:6484–6491, 1996. 261 Luis Serrano-Andrés. Estudio teórico del espectro electrónico de sistemas orgánicos. PhD thesis, Universitat de València, 1994. 262 Luis Serrano-Andrés, Manuela Merchán, Markus Fülscher, and Björn O. Roos. A theoretical study of the electronic spectrum of thiophene. Chem. Phys. Letters, 211:125–134, 1993. 263 Karl Kaufmann, Werner Baumeister, and Martin Jungen. Universal Gaussian basis sets for an optimum representation of Rydberg and continuum wavefunctions. J. Phys. B: At. Mol. Opt. Phys., 22:2223–2240, 1989. 264 M. P. Fülscher and B. O. Roos. The excited states of pyrazine: A basis set study. Theor. Chim. Acta, 87:403–413, 1994. 265 Kerstin Andersson. Multiconfigurational perturbation theory. PhD thesis, Lunds Universitet, 1992. 266 Markus P. Fülscher, Luis Serrano-Andrés, and Björn O. Roos. A theoretical study of the electronic spectra of adenine and guanine. J. Am. Chem. Soc., 119:6168–6176, 1997. 267 Luis Serrano-Andrés and Markus P. Fülscher. Theoretical study of the electronic spectroscopy of peptides. 1. The peptidic bond: Primary, secondary, and tertiary amides. J. Am. Chem. Soc., 118:12190–12199, 1996. 268 Manuela Merchán, Enrique Ortí, and Björn O. Roos. Theoretical determination of the electronic spectrum of free base porphin. Chem. Phys. Letters, 226:27–37, 1994. 269 Luis Serrano-Andrés and Björn O. Roos. A theoretical study of the indigoid dyes and their chromophore. Chem. Eur. J., 3:717–725, 1997. 270 K. Pierloot, E. Van Praet, L. G. Vanquickenborne, and B. O. Roos. Systematic ab initio study of the ligand field spectra of hexacyanometalate complexess. J. Phys. Chem., 97:12220–12228, 1993. 271 Kristine Pierloot, Jan O. A. De Kerpel, Ulf Ryde, and Björn O. Roos. Theoretical study of the electronic spectrum of plastocyanin. J. Am. Chem. Soc., 119:218–226, 1997. 272 Kristine Pierloot, Eftimios Tsokos, and Björn O. Roos. 3p–3d intershell correlation effects in transition metal ions. Chem. Phys. Letters, 214:583–590, 1993. 273 Manuela Merchán and Remedios González-Luque. Ab initio study on the low-lying excited states of retinal. J. Chem. Phys., 106:1112–1122, 1997. 274 Luis Serrano-Andrés, Manuela Merchán, Björn O. Roos, and Roland Lindh. Theoretical study of the internal charge transfer in aminobenzonitriles. J. Am. Chem. Soc., 117:3189–3204, 1995. 275 Manuela Merchán, Rosendo Pou-Amérigo, and Björn O. Roos. A theoretical study of the dissociation energy of $\ce{Ni2^+}$. A case of broken symmetry. Chem. Phys. Letters, 252:405–414, 1996. 276 M. P. Fülscher, S. Matzinger, and T. Bally. Excited states in polyene radical cations. An ab initio theoretical study. Chem. Phys. Letters, 236:167–176, 1995. 277 Mercedes Rubio, Manuela Merchán, Enrique Ortí, and Björn O. Roos. A theoretical study of the electronic spectra of the biphenyl cation and anion. J. Phys. Chem., 99:14980, 1995. 278 Vincenzo Barone and Maurizio Cossi. Quantum calculation of molecular energies and energy gradients in solution by a conductor solvent model. J. Phys. Chem. A, 102:1995–2001, 1998. 279 Maurizio Cossi, Nadia Rega, Giovanni Scalmani, and Vincenzo Barone. Polarizable dielectric model of solvation with inclusion of charge penetration effects. J. Chem. Phys., 114:5691–5701, 2001. 280 Gunnar Karlström. New approach to the modeling of dielectric media effects in ab initio quantum chemical calculations. J. Phys. Chem., 92:1315–1318, 1988. 281 Luis Serrano-Andrés, Markus P. Fülscher, and Gunnar Karlström. Solvent effects on electronic spectra studied by multiconfigurational perturbation theory. Int. J. Quantum Chem., 65:167–181, 1997. 282 Jacopo Tomasi and Maurizio Persico. Molecular interactions in solution: An overview of methods based on continuous distributions of the solvent. Chem. Rev., 94:2027–2094, 1994. 283 Maurizio Cossi and Vincenzo Barone. Solvent effect on vertical electronic transitions by the polarizable continuum model. J. Chem. Phys., 112:2427–2435, 2000. 284 Anders Bernhardsson, Roland Lindh, Gunnar Karlström, and Björn O. Roos. Direct self-consistent reaction field with Pauli repulsion: Solvation effects on methylene peroxide. Chem. Phys. Letters, 251:141–149, 1996. 285 W. F. Forbes and R. Shilton. Electronic spectra and molecular dimensions. III. Steric effects in methyl-substituted ${\alpha}$,${\beta}$-unsaturated aldehydes. J. Am. Chem. Soc., 81:786–790, 1959. 286 Marvin Douglas and Norman M. Kroll. Quantum electrodynamical corrections to the fine structure of helium. Ann. Phys., 82:89–155, 1974. 287 Bernd A. Hess. Relativistic electronic-structure calculations employing a two-component no-pair formalism with external-field projection operators. Phys. Rev. A, 33:3742–3748, 1986. 288 Per-Åke Malmqvist, Björn O. Roos, and Bernd Schimmelpfennig. The restricted active space (RAS) state interaction approach with spin–orbit coupling. Chem. Phys. Letters, 357:230–240, 2002. 289 Bernd A. Heß, Christel M. Marian, Ulf Wahlgren, and Odd Gropen. A mean-field spin–orbit method applicable to correlated wavefunctions. Chem. Phys. Letters, 251:365–371, 1996. 290 B. Schimmelpfennig. AMFI, an atomic mean-field spin–orbit integral program. Computer code, 1996. University of Stockholm. 291 Björn O. Roos and Per-Åke Malmqvist. On the effects of spin–orbit coupling on molecular properties: Dipole moment and polarizability of $\ce{PbO}$ and spectroscopic constants for the ground and excited states. Adv. Quantum Chem., 47:37–49, 2004. 292 Ulf Wahlgren. The effective core potential method. In Björn O. Roos, editor, Lecture Notes in Quantum Chemistry. European Summer School in Quantum Chemistry, volume 58 of Lecture Notes in Chemistry, pages 413–421. Springer-Verlag, Berlin, Germany, 1992. 293 Luis Seijo and Zoila Barandiarán. The Ab Initio model potential method: A common strategy for effective core potential and embedded cluster calculations. In Jerzy Leszczynski, editor, Computational Chemistry: Reviews of Current Trends, volume 4, pages 55–152. World Scientific, Singapore, 1999. 294 A. D. Buckingham. Permanent and induced molecular moments and long-range intermolecular forces. Adv. Chem. Phys., 12:107–142, 1967. 295 Guido Raos, Joseph Gerratt, David L. Cooper, and Mario Raimondi. Spin correlation in ${\pi}$-electron systems from spin-coupled wavefunctions. I. Theory and first applications. Chem. Phys., 186:233–250, 1994. 296 Guido Raos, Joseph Gerratt, David L. Cooper, and Mario Raimondi. Spin correlation in ${\pi}$-electron systems from spin-coupled wavefunctions. II. Further applications. Chem. Phys., 186:251–273, 1994. 297 R. Fletcher. A new approach to variable metric algorithms. Comput. J., 13:317–322, 1970. 298 Gunnar Karlström, Roland Lindh, Per-Åke Malmqvist, Björn O. Roos, Ulf Ryde, Valera Veryazov, Per-Olof Widmark, Maurizio Cossi, Bernd Schimmelpfennig, Pavel Neogrády, and Luis Seijo. MOLCAS: a program package for computational chemistry. Comput. Mater. Sci., 28:222–239, 2003. 299 G. A. Gallup and J. M. Norbeck. Population analyses of valence-bond wavefunctions and $\ce{BeH2}$. Chem. Phys. Letters, 21:495–500, 1973. 300 Thomas A. Halgren and William N. Lipscomb. The synchronous-transit method for determining reaction pathways and locating molecular transition states. Chem. Phys. Letters, 50:225–232, 1977. 301 Ola Engkvist, Per-Olof Åstrand, and Gunnar Karlström. Accurate intermolecular potentials obtained from molecular wave functions: Bridging the gap between quantum chemistry and molecular simulations. Chem. Rev., 100:4087–4108, 2000. 302 Isaiah Shavitt. Matrix element evaluation in the unitary group approach to the electron correlation problem. Int. J. Quantum Chem., 14-S12:5–32, 1978. 303 David L. Cooper, Robert Ponec, Thorstein Thorsteinsson, and Guido Raos. Pair populations and effective valencies from ab initio SCF and spin-coupled wave functions. Int. J. Quantum Chem., 57:501–518, 1996. 304 Thorstein Thorsteinsson and David L. Cooper. Modern valence bond descriptions of molecular excited states: An application of CASVB. Int. J. Quantum Chem., 70:637–650, 1998. 305 Ulf Ryde and Mats H. M. Olsson. Structure, strain, and reorganization energy of blue copper models in the protein. Int. J. Quantum Chem., 81:335–347, 2001. 306 Valera Veryazov, Per-Olof Widmark, Luis Serrano-Andrés, Roland Lindh, and Björn O. Roos. MOLCAS as a development platform for quantum chemistry software. Int. J. Quantum Chem., 100:626–635, 2004. 307 Ulf Ryde, Mats H. M. Olsson, Björn O. Roos, Jan O. A. De Kerpel, and Kristine Pierloot. On the role of strain in blue copper proteins. J. Biol. Inorg. Chem., 5:565–574, 2000. 308 Per E. M. Siegbahn, Jan Almlöf, J. Heiberg, and Björn O. Roos. The complete active space SCF (CASSCF) method in a Newton–Raphson formulation with application to the HNO molecule. J. Chem. Phys., 74:2384–2396, 1981. 309 C. G. Broyden. The convergence of a class of double-rank minimization algorithms 2. The new algorithm. J. Inst. Math. Appl., 6:222–231, 1970. 310 Ulf Ryde, Mats H. M. Olsson, Kristine Pierloot, and Björn O. Roos. The cupric geometry of blue copper proteins is not strained. J. Mol. Biol., 261:586–596, 1996. 311 Thorstein Thorsteinsson and David L. Cooper. Nonorthogonal weights of modern VB wavefunctions. Implementation and applications within CASVB. J. Math. Chem., 23:105–106, 1998. 312 Giovanni Li Manni, Simon D. Smart, and Ali Alavi. Combining the complete active space self-consistent field method and the full configuration interaction quantum Monte Carlo within a super-CI framework, with application to challenging metal-porphyrins. J. Chem. Theory Comput., 12:1245–1258, 2016. 313 Giovanni Li Manni and Ali Alavi. Understanding the mechanism stabilizing intermediate spin states in $\ce{Fe(II)}$-porphyrin. J. Phys. Chem. A, 122(22):4935–4947, 2018. 314 Giovanni Li Manni, Daniel Kats, David P. Tew, and Ali Alavi. Role of valence and semicore electron correlation on spin gaps in $\ce{Fe(II)}$-porphyrins. J. Chem. Theory Comput., 15:1492–1497, 2019. 315 George H. Booth, Alex J. W. Thom, and Ali Alavi. Fermion Monte Carlo without fixed nodes: A game of life, death and annihilation in Slater determinant space. J. Chem. Phys., 131:054106, 2009. 316 Catherine Overy, George H. Booth, N. S. Blunt, James J. Shepherd, Deidre Cleland, and Ali Alavi. Unbiased reduced density matrices and electronic properties from full configuration interaction quantum Monte Carlo. J. Chem. Phys., 141:244117, 2014. 317 Donald Goldfarb. A family of variable-metric methods derived by variational means. Math. Comput., 24:23–26, 1970. 318 D. F. Shanno. Conditioning of quasi-Newton methods for function minimization. Math. Comput., 24:647–656, 1970. 319 M. J. D. Powell. Recent advances in unconstrained optimization. Math. Program., 1:26–57, 1971. 320 Ove Christiansen, Jürgen Gauss, and Bernd Schimmelpfennig. Spin–orbit coupling constants from coupled-cluster response theory. Phys. Chem. Chem. Phys., 2:965–971, 2000. 321 B. H. Chirgwin and C. A. Coulson. The electronic structure of conjugated systems. VI. Proc. Roy. Soc. Lond. A, 201:196–209, 1950. 322 J. E. Dennis, Jr. and R. B. Schnabel. Least change secant updates for quasi-Newton methods. SIAM Rev., 21:443–459, 1979. 323 Thorstein Thorsteinsson, David L. Cooper, Joseph Gerratt, and Mario Raimondi. Symmetry adaptation and the utilization of point group symmetry in valence bond calculations, including CASVB. Theor. Chim. Acta, 95:131–150, 1997. 324 Martin Schütz and Roland Lindh. An integral direct, distributed-data, parallel MP2 algorithm. Theor. Chim. Acta, 95:13–34, 1997. 325 H. Bernhard Schlegel. Optimization of equilibrium geometries and transition structures. In K. P. Lawley, editor, Ab Initio Methods in Quantum Chemistry Part I, volume 67 of Advances in Chemical Physics, pages 249–286. John Wiley & Sons, Hoboken, NJ, USA, 1987. 326 R. Fletcher. Practical Methods of Optimization. John Wiley & Sons, Chichester, West Sussex, England, 2nd edition, 1987. 327 Warren J. Hehre. Practical Strategies for Electronic Structure Calculations. Wavefunction, Irvine, CA, USA, 1995. 328 Francesco Aquilante, Jochen Autschbach, Rebecca K. Carlson, Liviu F. Chibotaru, Mickaël G. Delcey, Luca De Vico, Ignacio Fdez. Galván, Nicolas Ferré, Luis Manuel Frutos, Laura Gagliardi, Marco Garavelli, Angelo Giussani, Chad E. Hoyer, Giovanni Li Manni, Hans Lischka, Dongxia Ma, Per Åke Malmqvist, Thomas Müller, Artur Nenov, Massimo Olivucci, Thomas Bondo Pedersen, Daoling Peng, Felix Plasser, Ben Pritchard, Markus Reiher, Ivan Rivalta, Igor Schapiro, Javier Segarra-Martí, Michael Stenrup, Donald G. Truhlar, Liviu Ungur, Alessio Valentini, Steven Vancoillie, Valera Veryazov, Victor P. Vysotskiy, Oliver Weingart, Felipe Zapata, and Roland Lindh. Molcas 8: New capabilities for multiconfigurational quantum chemical calculations across the periodic table. J. Comput. Chem., 37(5):506–541, 2016. 329 Alessio Valentini, Daniel Rivero, Felipe Zapata, Cristina García-Iriepa, Marco Marazzi, Raúl Palmeiro, Ignacio Fdez. Galván, Diego Sampedro, Massimo Olivucci, and Luis Manuel Frutos. Optomechanical control of quantum yield in Trans–Cis ultrafast photoisomerization of a retinal chromophore model. Angew. Chem. Int. Ed., 56(14):3842–3846, 2017. 330 Patrick Kimber and Felix Plasser. Toward an understanding of electronic excitation energies beyond the molecular orbital picture, 2020. 331 S. Knecht, S. Keller, J. Autschbach, and M. Reiher. A nonorthogonal state-interaction approach for matrix product state wave functions. J. Chem. Theory Comput., 12:5881–5894, 2016. 332 S. Keller, M. Dolfi, M. Troyer, and M. Reiher. An efficient matrix product operator representation of the quantum-chemical Hamiltonian. J. Chem. Phys., 143:244118, 2015. 333 S. Keller and M. Reiher. Spin-adapted matrix product states and operators. J. Chem. Phys., 144:134101, 2016. 334 S. Knecht, E. D. Hedegård, S. Keller, A. Kovyrshin, Y. Ma, A. Muolo, C. J. Stein, and M. Reiher. New approaches for ab initio calculations of molecules with strong electron correlation. Chimia, 70:244–251, 2016. 335 A. A. Granovsky. Extended multi-configuration quasi-degenerate perturbation theory: The new approach to multi-state multi-reference perturbation theory. J. Chem. Phys., 134:214113, 2011. 336 T. Shiozaki, W. Győrffy, P. Celani, and H.-J. Werner. Communication: Extended multi-state complete active space second-order perturbation theory: Energy and nuclear gradients. J. Chem. Phys., 135:081106, 2011. 337 Per Åke Malmqvist and Valera Veryazov. The binatural orbitals of electronic transitions. Mol. Phys., 110(19-20):2455–2464, 2012. 338 Attila Szabo and Neil S. Ostlund. Modern Quantum Chemistry. McGraw-Hill, New York, NY, USA, 1989. 339 S. Battaglia and R. Lindh. Extended dynamically weighted CASPT2: The best of two worlds. J. Chem. Theory Comput., 16:1555–1567, 2020. 340 Gerardo Raggi, Ignacio Fdez. Galván, Christian L. Ritterhoff, Morgane Vacher, and Roland Lindh. Restricted-variance molecular geometry optimization based on gradient-enhanced Kriging. J. Chem. Theory Comput., 16:3989–4001, 2020.