Multiconfiguration SCF and CI calculations on the open and closed forms of the ozone molecule

Abstract

The open and closed forms of the ozone molecule have been studied by SCF, MC SCF and MC CI calculations with a number of different basis sets and choices of configurations. It has been found that a double-zeta basis, augmented with polarisation functions, is needed to obtain an accurate description. The most accurate calculations give a bond length of 1.259 Å and a bond angle of 116.1° for the geometry of the open form, close to the experimental values 1.271 Å and 116.8°. The energy difference between the closed and open forms is calculated to be 128 and 120 kJ/mol at the MC SCF and MC CI levels respectively. The transition-state for the reaction between the two forms lies 156 kJ/mol above the open form within the MC SCF approximation: this barrier increases to 226 kJ/mol when the dynamical correlation is included.