# 4.2.22. GRID_IT¶

Warning

This program requires a submodule

## 4.2.22.1. 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.

## 4.2.22.2. 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.

## 4.2.22.3. Files¶

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

### 4.2.22.3.1. Input files¶

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.

### 4.2.22.3.2. Output files¶

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.

## 4.2.22.4. 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.

### 4.2.22.4.1. Optional general keywords¶

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 in a special mode (to produce the grid for non-cartesian points).

### 4.2.22.4.2. 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; PACK
ALL


An example for selection orbitals with partial occupation:

&GRID_IT
ORange = 0.01 1.99