MOLCAS manual:

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6.21 GRID_IT

6.21.1 Description

GRID_IT is an interface program for calculations of molecular orbitals and density in a set of cartesian grid points. The calculated grid can be visualized by GV program.

6.21.2 Dependencies

The GRID_IT program requires the communication file RUNFILE, produced by GATEWAY and an orbital file INPORB: SCFORB, RASORB, PT2ORB, generated by program SCF(calculated with RHF or UHF hamiltonian), RASSCF, or CASPT2, respectively.

6.21.3 Files

Below is a list of the files that are used/created by the program GRID_IT. Input files

RUNFILEFile for communication of auxiliary information generated by the program GATEWAY, or SEWARD.
INPORBSCFORB or another orbitals file (RASORB, CIORB, CPFORB, SIORB, PT2ORB) containing calculated orbitals. If used after SCF run, the information about one-electron energies is also retrieved. Output files

GRIDOutput grid file, with default extension grid - the only file needed for drawing program. By default this file is binary. In the case of UHF calculation, GRID_IT produces two files: a.grid and b.grid with grids for alpha and beta electrons. GV code could be used to combine grid files for visualization of total or spin density.

6.21.4 Input

Normally, it is no reason to change any default setting of calculated grid - the choice of appropriate grid size, net frequency, as well as choice of MO can be done automatically.

If user did not specified the selection of orbitals, GRID_IT makes a decision based on information in the InpOrb file. For example, if InpOrb contains data after SCF calculation, a set of orbitals around HOMO-LUMO gap will be used. If InpOrb contains active orbitals, they will be used as a default set.

Below follows a description of the input to GRID_IT. The keywords are always significant to four characters, but in order to make the input more transparent, it is recommended to use the full keywords. The GRID_IT program section of the MOLCAS input starts with the standard reference to the code:


Argument(s) to a keyword are always supplied on the next line of the input file, except when explicitly stated otherwise. Optional general keywords

TITLeOne line following this one is regarded as title.
NAMEOne line following this one is used for generation of grid filename in the form: 'Project.Name.grid'.
FILEOn the following line user can specify the filename, which will be used instead of INPORB (default).

SPARseSet up sparse cartesian net with 1 grid point per a.u. Note that quality of the grid can be poor. Default (without Sparse or Dense) is 3 points per a.u.
DENSeSet up net with 10 grid points per a.u. Note that using this option without choice of orbitals to draw you can produce very large output file.
GAPKeyword, followed by real equals to distance between the atomic nuclei in the molecule and the border of grid. Default value is 4.0 a.u.
ORBItalDirect specification of orbitals to show. Next line set up number of calculated grids. And at next line(s) pairs of integers - symmetry and orbital within this symmetry is given.
SELEctDirect specification of orbitals to show. Follows by one line in the format: symmetry:first_orbital-last_orbital (Ex: 1:2-7 2:5-8)

MULLikenCompute Mulliken charges separately for each occupied MO specified in the GRID_IT input. "LONG print" is an optional argument for more detailed printout.

NoSortDo not sort orbitals by occupation numbers and orbital energies

ORANgeFollowed by 2 numbers, to limit the interval of orbitals by occupation numbers.
ERANgeFollowed by 2 numbers, to limit the interval of orbitals by one-electron energies
ALLCalculate grids for all molecular orbitals. Using this keyword you can produce a huge output file!
TOTAlRequest to calculate a grid for the (correct) total density computed from contributions of all orbitals, instead of (default) just from the orbitals chosen by user.
VBThis keyword enables plotting of the orbitals from the latest CASVB orbitals. Note that the appropriate RASORB orbitals must be available in the INPORB file.
ATOMCalculate density at the position of atoms.
ASCIIKeyword for ASCII format of output file. NOTE that GV automatically recognizes both (binary and ASCII) formats. This keyword is useful if a calculation of the grid file and visualization should be done on computers with different architecture. Also note, that if you use native MS Windows compilers to build GV you have to pass resulting grid file via unix2dos.

CUBEKeyword to produce a set of ASCII files for MOLDEN visualization. To import the file to MOLDEN, select 'Read Cube' in density mode.
NPOIntsKeyword, followed by 3 integers equal to number of grid points in x, y, z directions. Using for non-automatic choice of grid network.
GRIDKeyword to set manually coordinates of a grid. Followed by number of cartesian coordinates, and on next lines - x y z coordinates of a grid (in a.u.) Input example

An example for high quality picture, containing selected orbitals (from symmetry 1 and 4):


An example for screen quality picture, containing all orbitals:


An example for selection orbitals with partial occupation

ORange  =  0.01  1.99

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Next: 6.22 guessorb Up: 6. Programs Previous: 6.20 geo