The potential energy surfaces of the six lowest singlet states of HOCl: global optimization of parameters for an extended anti-Morse function and a diatomics-in-molecules (DIM) model

Abstract

The potential energy function of the electronic ground state and the five lowest excited singlet states of HOCl are described by analytical functions. The parameters contained in these functions were optimized through a global fit to abinitio data from Nanbu and Iwata (J. Phys. Chem., 1992, 96, 2103), employing a genetic algorithm. An improved parametrization of the functional form originally proposed by Nanbu and Iwata was found, which uses 12 parameters for each surface. A fit of equal quality was obtained with functions derived with the diatomics-in-molecules (DIM) approach. These describe all 6 singlet states simultaneously with a common parameter set of only 20 parameters. Within this model the extension for including the O–H distance as an additional coordinate is straightforward.