INDO/S Excited-State Calculations in MOPAC

Rebecca Gieseking

Abstract

The INDO/S Hamiltonian is parametrized specifically for spectroscopic (excited state) properties. I will highlight the capabilities of the INDO/S code that I recently incorporated into MOPAC2016. The new code enables the calculation of excited states using the INDO/S Hamiltonian combined with a configuration interaction (CI) approach using single excitations (CIS), single and double excitations (CISD), or multiple reference determinants (MRCI). INDO/CI is one of the few low-cost computational methods capable of accurately modeling states with substantial double-excitation character. Solvent corrections to the ground-state and excited-state energies can be computed using the COSMO implicit solvent model, incorporating state-specific corrections to the excited states based on the solvent refractive index. This code produces physically reasonable electronic structures, absorption spectra, solvatochromic shifts, and nonlinear optical properties for systems up to hundreds of atoms, and for both organic molecules and metal clusters.