Theory of lone pairs. IV. Molecular ion hole states of ten‐electron hydrides. Molecular ionization potentials and proton affinities by direct SCF calculations

Abstract

Closed-shell SCF calculations on the ground states and direct SCF calculations on the ionized doublet states were carried out for a series of ten-electron hydrides. The correlation of ionization potentials with the degree of protonation and the nuclear charge has been studied for hole states derived from excitation out of both the core and valence molecular orbitals. Calculated proton affinities of the ground states and hole states derived from a given symmetry orbital show a similar trend to that of the ionization potentials.

Ansatz for the evaluation of the relativistic contributions to core ionization energies in complex molecules involving heavy atoms

“…Successive steps of approximation for calculating these excitation and ionization energies can be summarized as follows: Initial step: Koopmans' theorem (no relaxation: NX) applied to nonrelativistic (NT) self‐consistent field (SCF) Hartree‐Fock (HF) orbital energies (no correlation: NC); Further step: difference between total SCF energies computed separately for the ground and excited states, yielding ΔSCF results (including relaxation: YX). This implies using specific methods that avoid the problem of variational collapse for core‐hole states 14–20; Further step: difference between correlated (YC) total energies: EHF, CI, DFT, MBPT, MCSCF, CC, EC, etc., computed separately for the excited and ground states, yielding results now including both relaxation and correlation (ΔXC), but not yet relativity; Ultimate step: difference between relativistic and correlated (YTC) total energies: CI‐DBF, REL‐DFT, MC‐DBF, CC‐DBF, etc., for the excited and ground states, yielding results including all effects (ΔXCT). …”

“…Further step: difference between total SCF energies computed separately for the ground and excited states, yielding ΔSCF results (including relaxation: YX). This implies using specific methods that avoid the problem of variational collapse for core‐hole states 14–20;…”