Quantum-mechanical calculations of the dynamic polarizability of atoms and molecules

Abstract

Two variants of nonstationary perturbation theory are commonly used in the quantum-mechanical calculations of the dynamic polarizability of atomic and molecular systems within the one-electron approximation. These are the nonstationary bound Hartree-Fock perturbation theory and nonstationary variational perturbation theory combined with the method of superposition of singly excited configurations. In order to obtain stable results for dynamic polarizability for small as opposed to polyatomic molecules in nonempirical calculations atomic orbital basis sets containing several tens of Gaussian functions are required. The spectral decomposition method in this case requires requires a vast amount of computer time. In this paper the authors have developed an iterative method of solution for the two perturbation theory variants in which the transformation of integrals has to be performed only for two indices and consequently results in a reduction of computer time required. In addition, they have successfully used basis sets containing more than forty Gaussian orbitals in their simulation of the dynamic polarizability of small molecules.