Generating Localised Orbitals

orto can generate localised orbital gbw and molden files using orto gen loc.

This wraps orca_loc and generates cube files without the time need to write input files.

Setup

To use this feature, you need to first set the orto_orca_load environment variable - this specifies the command used to load the ORCA module on your system.

Typically a module system like Lmod or Environment Modules is used to manage software on HPC systems, and you will need to set this variable accordingly.

For example, when using Environment Modules, this may be set as

    export orto_orca_load="orca/6.1.1"

We advise that you set this to the version of ORCA you use most frequently.

Alternatively, you can provide the --orca_load optional argument in orto gen loc and specify the command to load ORCA - this overrides the environment variable and so can be used to submit jobs with different versions of ORCA.

Usage

To generate cube files for your canonical MOs, run

    orto gen loc <gbw_file> <method> <orb_range> [options]

where <gbw_file> is the path to your ORCA .gbw file, <metod> is indicates which localisation method to use (see below), and <orb_range> indicates the range of orbitals to localise as two numbers separated by a hyphen.

This will then submit a batch job to generate the localised orbitals.

Methods

All methods of orca_loc are available, and are referred to as

  • fb: Foster-Boys

  • fb_new: ORCA’s NEWBOYS Foster-Boys algorithm

  • fb_aug: ORCA’s Augmented Hessian Foster-Boys (AHFB) algorithm

  • pm: Pipek-Mezey

  • iaoibo: Knizia’s original IAOIBO using PM functional

  • iaoibo_boys: Knizia’s IAOIBO using FB functional

Memory

The amount of memory to use in the cube file generation job can be specified using the --memory keyword argument, by default, 1 GB is used.

Alpha and Beta MOs

By default, the alpha MOs will be localised.

To use beta MOs, use the --spin beta flag in orto gen loc.

Other Arguments

Additional command line arguments for orto gen orbs can be listed by running

orto gen orbs -h

Example - Benzene Orbitals

From this file, you can use orto to localise the occupied canonical MOs of benzene using the IAOIBO method.

orto gen loc benzene.gbw iaoibo 0-20

This creates a jobscript (benzene_loc_job.sh) which is then submitted to the scheduler. All output from orca_loc will be written to benzene_loc.%d.o.

After this job finishes, the files benzene_loc.gbw and benzene_loc.molden will be present in the same directory as benzene.gbw.