# Printing orbital densities to cube files¶

## Description¶

This module prints molecular orbital densities in the Gaussian Cube format. It can be used to view the shape and extent of relativistic or gauge-including molecular orbitals, which cannot be viewed in Molden due to the use of complex basis functions or the four-component framework.

A separate .cub file is generated for each printed orbital, plus one for the total electron density. The axis vectors are simply the Cartesian x, y, and z axes.

In addition, one can print the relaxed electron density in MP2, SA-CASSCF, and CASPT2 force calculations as well. See nuclear gradient and derivative coupling and the example below.

Command: moprint

## Keywords¶

paired

Description: Determined whether we plot spatial MOs (true) or spin MOs.
Datatype: bool
Default: True, unless we are printing 4-component orbitals generated with an external magnetic field.
Recommendation: Use the default.

orbitals

Description: Indices of the molecular orbitals to be printed.
Datatype: Vector of integers
Default: Prints the active orbitals from CASSCF, and the frontier orbitals from Hartree–Fock

start_pos

Description: Coordinates for one corner of the box within which densities are printed.
Datatype: Array of 3 doubles
Default: A position is chosen so that all atoms (except the dummy atoms) are at least $$4 a_0$$ from the edges of the box.
Recommendation: Use the default.

inc_size

Description: Distances between adjacent gridpoints in each of the three dimensions.
Datatype: Array of 3 doubles
Default: $$0.25 a_0$$ in each direction.
Recommendation: Use the default.

angstrom

Description: Unit of the “inc_size” parameter
Datatype: bool
Default: False (meaning Bohr; set to true for angstrom)

mo_filename

Description: Name of the MO cube file
Datatype: string
Default: “mo”

density_filename

Description: Name of the density cube file
Datatype: string
Default: “density”

## Example¶

### Sample input: Print MO¶

Write molecular orbitals:

{ "bagel" : [

.... energy calculation....

{
"title" : "moprint",
"inc_size" : [ 0.20, 0.20, 0.20 ],
"orbitals" : [ 14, 15, 16, 17, 18, 19, 20, 21, 22 ]
}

]}


### Sample input: Print relaxed density¶

Write relaxed density to the file density_0.cub from the XMS-CASPT2 force calculation:

{ "bagel" : [

{
"title" : "molecule",
"basis" : "svp",
"df_basis" : "svp-jkfit",
"geometry" : [
{ "atom" : "Li", "xyz" : [ 0.000000, 0.000000, 6.000000] },
{ "atom" : "F",  "xyz" : [ 0.000000, 0.000000, 0.000000] }
]
},

{
"title" : "force",
"target" : 0,
"density_print" : true,
"moprint" : {
"density_filename" : "density_0",
"inc_size" : [ 0.20, 0.20, 0.20 ]
},
"method" : [ {
"title" : "caspt2",
"smith" : {
"method" : "caspt2",
"shift" : 0.2,
"frozen" : true
},
"nstate" : 4,
"nact" : 4,
"nclosed" : 3
} ]
}

]}