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Subsections

8.20 `GRID_IT`

8.20.1 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 LUSCUS program.

8.20.2 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.

8.20.3 Files

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

8.20.3.1 Input files

File Contents
RUNFILE File for communication of auxiliary information generated by the program GATEWAY.
INPORB SCFORB 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.

8.20.3.2 Output files

File Contents
LUS Output file in LUSCUS format, with default extension .lus — the only file needed for drawing program. In the case of UHF calculation, GRID_IT produces two files: a.lus and b.lus with grids for alpha and beta electrons. LUSCUS code could be used to combine grid files for visualization of total or spin density.
GRID Obsolete format of the grid file, can be converted to Cube files using the grid2cube tool. In order to generate a file with data written in grid format, keyword NOLUSCUS should be used.

8.20.4 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:
&GRID_IT

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

8.20.4.1 Optional general keywords

Keyword	Meaning
TITLe	One line following this one is regarded as title.
NAME	One line following this one is used for generation of grid filename in the form: ``Project.Name.lus''.
FILE	On the following line user can specify the filename, which will be used instead of INPORB (default). For example: FileOrb=$CurrDir/$Project.ScfOrb.
SPARse	Set 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.
DENSe	Set 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.
GAP	Keyword, 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.
ORBItal	Direct 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.
SELEct	Direct specification of orbitals to show. Follows by one line in the format: symmetry:first_orbital-last_orbital (Ex: 1:2-7 2:5-8)
MULLiken	Compute Mulliken charges separately for each occupied MO specified in the GRID_IT input. "LONG print" is an optional argument for more detailed printout.
NoSort	Do not sort orbitals by occupation numbers and orbital energies
ORANge	Followed by 2 numbers, to limit the interval of orbitals by occupation numbers.
ERANge	Followed by 2 numbers, to limit the interval of orbitals by one-electron energies
ALL	Calculate grids for all molecular orbitals. Using this keyword you can produce a huge output file!
TOTAl	Request 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.
VB	This keyword enables plotting of the orbitals from the latest `CASVB` orbitals. Note that the appropriate `RASORB` orbitals must be available in the `INPORB` file.
ATOM	Calculate density at the position of atoms.
ASCII	Obsolete keyword for ASCII format of output file. This option can only be used in combination with NOLUSCUS. This keyword is useful if a calculation of the grid file and visualization should be done on computers with different architectures.
NPOInts	Keyword, followed by 3 integers equal to number of grid points in x, y, z directions. Using for non-automatic choice of grid network.
GRID	Keyword 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.)
GORI	Keyword to set manually the parallelepiped spanning a grid. Followed by four lines of three columns each. The first line defines the x y z location of the origin, the next three lines are three linearly independent vectors that span the parallelepiped of the grid. This keyword requires NPOINTS to build up the lattice of gridpoints.
NOLUSCUS	Produce data file in obsolete format (which can be read by old (before 2015) versions of `GV`).
XFIELD	Use `Grid_It` it in a special mode (to produce the grid for non-cartesian points).

8.20.4.2 Input example

An example for high quality picture, containing selected orbitals (from symmetry 1 and 4):
&GRID_IT Dense Select 1:10-20,4:3-7

An example for screen quality picture, containing all orbitals:
&GRID_IT SPARSE ALL

An example for selection orbitals with partial occupation
&GRID_IT ORange = 0.01 1.99

Program Grid_it also can do simple arithmetic operations with produces luscus files. In this case the input is different from the described above.

User have to specify two compusory keywords (LUS1 and LUS2) with teh file name as a parameter, and an operation PLUS or MINUS (the latter is default). It is also possible to specify a name of the output file by using keyword name.

An example. The first two runs generate two luscus files: $Project.STO.lus and $Project.ANO.lus , which later are transformed into the third file: $Project.Difference.lus

&GATAWAY coord=$MOLCAS/Coord/Benzene.xyz Basis=STO-3G &SEWARD &SCF &GRID_IT ALL NAME=STO &GATAWAY coord=$MOLCAS/Coord/Benzene.xyz Basis=ANO-S-VDZP &SEWARD &SCF &GRID_IT ALL NAME=ANO &GRID_IT LUS1=$CurrDir/STO.lus LUS2=$CurrDir/ANO.lus MINUS NAME=Difference