Electron affinity of Li7 calculated with the inclusion of nuclear motion and relativistic corrections

Hylleraas-Configuration Interaction study of the 1S ground state of the negative Li ion

In a previous work Sims and Hagstrom [J. Chem. Phys. 140, 224312 (2014)] reported Hylleraas-Configuration Interaction (Hy-CI) method variational calculations for the neutral atom and positive ion ¹S ground states of the beryllium isoelectronic sequence. The Li^- ion, nominally the first member of this series, has a decidedly different electronic structure. This paper reports the results of a large, comparable calculation for the Li^- ground state to explore how well the Hy-CI method can represent the more diffuse L shell of Li^- which is representative of the Be(2sns) excited states as well. The best non-relativistic energy obtained was -7.500 776 596 hartree, indicating that 10 - 20 nh accuracy is attainable in Hy-CI and that convergence of the r₁₂r₃₄ double cusp is fast and that this correlation type can be accurately represented within the Hy-CI model.

An algorithm for quantum mechanical finite-nuclear-mass variational calculations of atoms with L = 3 using all-electron explicitly correlated Gaussian basis functions

A new algorithm for quantum-mechanical nonrelativistic calculation of the Hamiltonian matrix elements with all-electron explicitly correlated Gaussian functions for atoms with an arbitrary number of s electrons and with three p electrons, or one p electron and one d electron, or one f electron is developed and implemented. In particular the implementation concerns atomic states with L = 3 and M = 0. The Hamiltonian used in the approach is obtained by rigorously separating the center-of-mass motion from the laboratory-frame all particle Hamiltonian, and thus it explicitly depends on the finite mass of the nucleus. The approach is employed to perform test calculations on the lowest (2)F state of the two main isotopes of the lithium atom, (7)Li and (6)Li.