INDO/X: A new semiempirical method for excited states of organic and biological molecules

he 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 moleculesThis work has been supported by grants CTQ2011-26573 from Ministry of Science and Innovation, Spain (MICINN