# A general program for computing angular integrals of the Breit–Pauli Hamiltonian with non-orthogonal orbitals

## Description

Abstract The BREIT_NO program performs the angular integrations necessary for expressing the matrix elements of the Breit–Pauli Hamiltonian as a linear combination of radial integrals. Any amount of non-orthogonality between the orbitals may be present leading to overlap factors in the matrix elements. The calculations follow the method based on the representation of configuration wave functions through the Slater determinants. All matrix elements for a given list of configuration states may be evalua... Title of program: BREIT_NO Catalogue Id: ADLA_v1_0 Nature of problem In many atomic processes involving inner atomic shells, the relaxation of electron orbitals plays an important role. The relaxation can be most naturally taken into consideration by using non-orthogonal orbitals for the initial and final state. In atomic structure calculations, the rate of convergence of the many-configuration expansion to an acceptable accuracy may be much faster if the orbitals associated with different configurations and terms are not necessarily required to be orthogonal. Th ... Versions of this program held in the CPC repository in Mendeley Data ADLA_v1_0; BREIT_NO; 10.1016/S0010-4655(99)00441-5 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2019)