Calculation of atomic polarisabilities by finite-difference methods. Part 2.—Study of the beryllium isoelectronic sequence

Abstract

Finite–difference methods are used in a study of the polarisabilities of the beryllium isoelectronic sequence Li^– to Ne⁶⁺. Two approximations to the Coupled Perturbed Hartree–Fock scheme are considered for the evaluation of static dipole and quadrupole polarisabilities, it being demonstrated that, provided the appropriate perturbation equations are solved accurately, both yield results which differ only marginally from those obtainable from the fully coupled method. Similarly encouraging calculations of the dynamic polarisability of Be are also recorded. The practicability of accurate polarisability calculations on medium and large systems is briefly discussed in the light of the present results.