Anatomy of relativistic energy corrections in light molecular systems

G. Tarczay, A. Császár, Wim Klopper, Harry M. Quiney

Research output: Contribution to journalArticle

106 Citations (Scopus)

Abstract

Relativistic energy corrections which arise from the use of the Dirac-Coulomb Hamiltonian, and the Gaunt and Breit interaction operators, plus Lamb-shift effects have been determined for the global minima of the ground electronic states of C2H6, NH3, H2O, [H,C,N], HNCO, HCOOH, SiC2, SiH3 -, and H2S, and for barrier characteristics for these molecular systems (inversion barrier of NH3 and SiH3 -, barrier to linearity of H2O, H2S, and HNCO, rotational barrier of C2H6, difference between conformations of HCOOH (Z/E) and SiC2 (linear/T-shaped), and isomerization barrier of HCN/HNC). The relativistic calculations performed at the Hartree-Fock and the highly correlated CCSD(T) levels employed a wide variety of basis sets. Comparison of the perturbational and the four-component fully variational results indicate that the Coulomb-Pauli Hamiltonian and the lowest order Hamiltonian of direct perturbation theory (DPT(2)) are highly successful for treating the relativistic energy effects in light molecular systems both at a single point on the potential energy hypersurface and along the surface. Electron correlation contributions to the relativistic corrections are relatively small for the systems studied, and are comparable with the 2-electron Darwin correction. Corrections beyond the Dirac-Coulomb treatment are usually rather small, but may become important for high accuracy ab initio calculations.

Original languageEnglish
Pages (from-to)1769-1794
Number of pages26
JournalMolecular Physics
Volume99
Issue number21
DOIs
Publication statusPublished - Nov 10 2001

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Hamiltonians
anatomy
Anatomy
Electrons
Light
Electron correlations
Electronic states
Isomerization
Potential energy
Conformations
energy
Mathematical operators
isomerization
linearity
electrons
perturbation theory
potential energy
inversions
operators
shift

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Anatomy of relativistic energy corrections in light molecular systems. / Tarczay, G.; Császár, A.; Klopper, Wim; Quiney, Harry M.

In: Molecular Physics, Vol. 99, No. 21, 10.11.2001, p. 1769-1794.

Research output: Contribution to journalArticle

Tarczay, G. ; Császár, A. ; Klopper, Wim ; Quiney, Harry M. / Anatomy of relativistic energy corrections in light molecular systems. In: Molecular Physics. 2001 ; Vol. 99, No. 21. pp. 1769-1794.
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