New efficient algorithm for the calculation of energy levels of AB3 type molecules

Abstract

This paper illustrates a method for the construction of a symmetry-adapted contracted angular basis set for AB3 molecules. Simple formulas that use this basis set for calculations of the angular matrix elements of the kinetic energy (KE) operator and angular matrix elements of potential energy surface (PES) are reported. The efficient recursive algorithm based on the tensorial formalism is used for the calculation of vibrational matrix elements. The symmetric form of vibration KE operators without the sin(q)−2 type singularity is applied. A good basis set convergence for the calculations of vibrational levels of the PH3 molecule is demonstrated.