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Subsections
6.27 LoProp
The program
LoProp
is a tool to compute molecular properties based on the oneelectron density
or transitiondensity and oneelectron integrals like charges, dipole moments and polarizabilities.
LoProp allows to partition such properties into atomic and interatomic
contributions. The method requires a subdivision of the atomic orbitals into
occupied and virtual basis functions for each atom in the molecular system.
It is a requirement for the approach to have any physical significance that the
basis functions which are classified as "occupied" essentially are the atomic
orbitals of each species. It is therefore advisable to use an ANO type basis set,
or at least a basis set with general contraction.
The localization procedure is organized into a series of orthogonalizations of
the original basis set, which will have as a final result a localized
orthonormal basis set.
Note that this module does not operate with symmetry.
A static property, which can be evaluated as an expectation value, like a charge,
a component of the dipole moment or an exchangehole dipole moment,
is localized by transforming the integrals
of the property and the oneelectron density matrix to the new basis and
restricting the trace to the subspace of functions of a single center or the
combination of two centers.
The molecular polarizability is the first order derivative of the dipole moment
with respect to an electric field and the localized molecular polarizability
can be expressed in terms of local responses. In practical terms a calculation
of localized polarizabilities will require to run seven energy calculations. The
first one is in the absence of the field and the other six calculations are in
the presence of the field in the x,y,z axis respectively.
For a detailed description of the method and its implementation see
[61].
6.27.1 Dependencies
The dependencies of the LoProp module is the union
of the dependencies of the SEWARD, and
the program used to perform the energy calculation, namely
the SCF, MBPT2,
RASSCF, or CASPT2 module. The user
can also provide LoProp with a density matrix as input; then
LoProp only depends on SEWARD. The oneelectron
transition density matrix can also be localized to compute, for
example, Förster transition probabilities; then LoProp
depends on RASSI to compute the transition density.
6.27.2 Files
The files of the LoProp module is the union
of the files of the SEWARD module,
and the SCF or MBPT2,
or RASSCF, or CASPT2 module.
An exception is if a density matrix is given as input or
when a transition density matrix is localized, see below.
File  Contents

USERDEN  The density matrix given as input when the keyword USERdensity is
included in the input. The density matrix should be of the following
form: triangularly stored ((1,1),(2,1),(2,2),(3,1) etc.) with
all offdiagonal elements multiplied by two.

USERDEN1  The density matrix for a fieldperturbed calculation (X = +delta)

USERDEN2  The density matrix for a fieldperturbed calculation (X = delta)

USERDEN3  The density matrix for a fieldperturbed calculation (Y = +delta)

USERDEN4  The density matrix for a fieldperturbed calculation (Y = delta)

USERDEN5  The density matrix for a fieldperturbed calculation (Z = +delta)

USERDEN6  The density matrix for a fieldperturbed calculation (Z = delta)

TOFILE  The oneelectron transition density matrix, which optionally can be
put to disk by RASSI, see its manual pages.

In addition to the standard output unit LoProp will generate the following
file.
File  Contents

MpProp  File with the input for NEMO.

6.27.3 Input
This section describes the input to the
LoProp program. The program name is:
&LOPROP
There are no compulsory keywords.
Keyword  Meaning

NOFIeld  The calculation is run in the absence of a field and only static properties
like charges and dipole moments are computed. The default is to go beyond the
static properties.

DELTa  The magnitude of the electric field in the finite field perturbation
calculations to determine the polarizabilities. Default value is 0.001 au.

ALPHa  A parameter in the penalty function used for determining the
charge fluctuation contribution to the polarizabilities. See eq. 17 in
[61]. The default value of 7.14 is good for small molecules
(less than 50 atoms). For larger molecules, a smaller alpha (e.g. 2.0)
may be needed for numerical stability.

BOND  Defines the maximum allowed bond length based on the ratio compared to
BraggSlater radii. All contributions in bonds longer than this radius will
be redistributed to the two atoms involved in the bond, so the the total
molecular properties are left unaltered. The default value is 1.5.

MPPRop  Defines the maximum l value for the multipole moments written to the MpProp
file. If the value specified is larger than the highest multipole moment
calculated it will be reset to this value, which is also the default value.
The 'MULTipoles' keyword in Seward can change the default value.

EXPAnsion center  Defines which points will be used as the expansion centers for the bonds. The
next line must contain either 'MIDPoint' in order just to use the midpoint of
the bond or 'OPTImized' in order to let LoProp move the expansion center along
the bond. The latter is still highly experimental!

USERdensity  No density matrix is computed instead it is read as an input from the file
USERDEN. This enables LoProp to obtain localized
properties for densities that currently can not be computed with MOLCAS.
If the keyword NOFIeld is not given, six additional files are
required (USERDEN1USERDEN6), each containing the density matrix of
a perturbed calculation, see above. Observe the form
of USERDEN, see above.

TDENsity  This keyword signals that the oneelectron density matrix which is to
be read comes from the TOFILE file generated by RASSI. The
keyword is followed by two integers that gives number of initial and
final state of the transition. For example, if it is the transition
density between the first and second state which should be localized,
the integers should be 1 and 2. The keyword implies NOFIeld

XHOLe  The exchange hole dipole moment is computed, localized and given
as additional output.
This quantity can be used to compute local dispersion coefficients
according to Becke and Johnson.[62] The numerical integration
routine in MOLCASis used.

Below follows an example input to determine the localized charges, and dipole
moments of acetone at the CASSCF level of theory.
&GATEWAY
Title = acetone
Coord = $MOLCAS/Coord/Acetone.xyz
Basis = ANOLVDZP
Group = C1
&SEWARD
&SCF
Occupation = 15
&RASSCF
SPIN = 1
SYMMETRY = 1
NACTEL = 4 0 0
INACTIVE = 13
RAS2 = 4
&LOPROP
NoField
Expansion Center
Optimized
Bond = 1.5
MpProp = 2
In case the density matrix is given as input the input is of the
form below (where $CurrDir is a variable defined by the user pointing
to the directory where the input density is).
&Gateway
Coord = Water.xyz
Basis = 631G*
Group = C1
&Seward
>>COPY $CurrDir/Density $WorkDir/$Project.UserDen
&LoProp
UserDensity
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