INDO in MOPAC2016

INDO code

We have implemented the INDO/S Hamiltonian into the public release of MOPAC2016, now available as an open-source package (https://github.com/openmopac/mopac). The INDO/S Hamiltonian (or equivalently, ZINDO/S) has parameters designed specifically to reproduce vertical excited-state energies using a configuration interaction approach with single excitations (CIS). We have shown that the solvatochromic shifts computed using INDO/S and the COSMO solvent model are in good agreement with experimental results and comparable to the accuracy of typical DFT functionals. The INDO/S Hamiltonian has also shown success in understanding excited states with large double-excitation character using either single and double excitations (CISD) or a multi-reference approach (MRCI). The code also includes our INDO/S parameters that reproduce the optical properties of silver clusters.

The key features we have implemented in this code are:

• • INDO/S Hamiltonian for main-group elements and transition metals (note that parameters for many transition metals are relatively untested)

  • All default INDO/S parameters can be modified by reading in parameters from an external file

  • INDO/CI using single excitations (CIS), single and double excitations (CISD), and multiple reference determinants (MRCI)

  • COSMO implicit solvation with state-specific excited-state corrections for all CI methods

  • Electric field effects on ground and excited states

Several examples of typical input and output files are available from http://openmopac.net/manual/INDO_Examples.html.

Analysis Scripts

We have also released several Python scripts to analyze INDO output files from MOPAC2016. These scripts are available at https://github.com/gieseking-lab/indo-analysis.

The scripts are:

• absorption.py: Computes a Lorentzian-broadened absorption spectrum.

• cubegen.py: Computes cube files in Gaussian .cub format for visualization of molecular orbitals, transition densities, and changes in electron density.

• polarizability.py: Computes the polarizability of the system at a given frequency.

• displace.py: Creates a MOPAC input file for a geometry displaced along a normal mode. 

• raman.py: Computes the frequency-specific Raman intensity of vibrational modes.