The ab initio model potential method with the spin-free relativistic scheme by eliminating small components Hamiltonian

Abstract

A relativistic ab initio model potential ͑AIMP͒ for Pt, Au, and Hg atoms has been developed using a relativistic scheme by eliminating small components ͑RESC͒ in which the 5p, 5d, and 6s electrons are treated explicitly. The quality of new RESC-AIMP has been tested by calculating the spectroscopic properties of the hydrides of these elements using the Hartree-Fock and coupled cluster with singles and doubles ͑CCSD͒ methods. The agreement with reference all-electron RESC calculations is excellent. The RESC-AIMP method is applied successfully in the investigation of the spectroscopic constants of Au 2 and Hg 2 using the CCSD method with a perturbative estimate of the contributions of triples. The ground state of Pt 2 is also determined by RESC-AIMP with the second-order complete active space perturbation method. The results show that scalar relativistic effects on the valence properties are well described by the RESC-AIMP method. The effect on the basis set superposition error on the spectroscopic constants is also examined.

The permanent electric dipole moment of holmium monoxide, HoO

“…Most available ab initio programs for molecular electronic structure calculations that attempt to describe these effects are single component codes employing a perturbation approach using, for example, the Briet-Pauli Hamiltonian operator resulting from the Foldy-Wouthuysen transformation [9]. Developing methodologies for treating these approximate operators, and more importantly determining their ability to accurately describe the complete range of relativistic effects, are an active research area [8][9][10][11][12]. A comparison of predicted permanent electric dipole moments, which are primarily dependent upon the chemically relevant valence electrons, with experimentally determined values for molecules containing lanthanides is especially relevant in assessing the effectiveness of these methodologies.…”

Frozen core potential scheme with a relativistic electronic Hamiltonian: Theoretical connection between the model potential and all-electron treatments

“…(a) the valence relativistic effect and (b) the accurate core-valence relativistic effect using an -5 -electronic Hamiltonian. In the former effect, the AIMP method has already been extended to use the valence relativistic Hamiltonian within the relativistic scheme by eliminating the small component [40] and third-order Douglas-Kroll-Hess (DKH) methods [37]. In the latter effect, two conditions should be satisfied.…”

Third-order Douglas–Kroll ab initio model potential for actinide elements

“…[9][10][11][12][13][14][15][16][17][18][19][20] However, relativistic effects for the heavy elements such as actinides are very significant and a highly accurate treatment is required, even at the scalar relativistic level of theory. The main purpose of this study is to develop highly accurate AIMP for all actinide elements from Th to Lr by means of the third-order Douglas-Kroll ͑DK3͒ approximation.…”