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Updated: Mar 30, 2026

Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
INDO/X: A New Semiempirical Method for Excited States of Organic and Biological Molecules
1Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Barcelona, Spain.
Abstract:
The semiempirical method INDO/S is a well-known computational tool for calculating spectroscopic properties of molecular systems. This scheme has been modified and reparameterized using the TBE-2 benchmark excitation energies and oscillator strengths. The developed method referred to as INDO/X provides significant improvements over INDO/S. The mean absolute deviations of the INDO/X excitation energies relative to the TBE-2 data is 0.26 eV for singlet states and 0.33 eV for triplet states. The corresponding values for INDO/S are 0.56 and 0.64 eV. Also, the oscillator strengths estimated with INDO/X are in good agreement with the benchmark data. The proposed method is very fast and may be applied to large organic and biological molecules.
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