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.

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

ngrid

Description: Number of gridpoints in each dimension
Datatype: Array of 3 integers
Default: 61 gridpoints in each direction
Recommendation: It is often reasonable to reduce this parameter, perhaps to [41, 41, 41], in order to lower the time needed to write and read cube files.

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 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: If “start_pos” is not specified, an increment is chosen so that all atoms are at least \(4 a_0\) from the edges of the box.
Otherwise, the default is \(0.25 a_0\) 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)

Example

Sample input

Write molecular orbitals:

{ "bagel" : [

.... energy calculation....

{
  "title" : "moprint",
  "ngrid" : [ 41, 41, 41 ],
  "orbitals" : [ 14, 15, 16, 17, 18, 19, 20, 21, 22 ]
}

]}