An ab initio study of nuclear volume effects for isotope fractionations using two-component relativistic methods

Keisuke Nemoto, Minori Abe, Junji Seino, Masahiko Hada

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8 Citations (Scopus)

Abstract

We investigate the accuracy of two-component Douglas-Kroll-Hess (DKH) methods in calculations of the nuclear volume term (≡ lnKnv) in the isotope fractionation coefficient. lnKnv is a main term in the chemical equilibrium constant for isotope exchange reactions in heavy element. Previous work based on the four-component method reasonably reproduced experimental lnKnv values of uranium isotope exchange. In this work, we compared uranium reaction lnKnv values obtained from the two-component and four-component methods. We find that both higher-order relativistic interactions and spin-orbit interactions are essential for quantitative description of lnKnv. The best alternative is the infinite-order Douglas-Kroll-Hess method with infinite-order spin-orbit interactions for the one-electron term and atomic-mean-field spin-same-orbit interaction for the two-electron term (IODKH-IOSO-MFSO). This approach provides almost equivalent results for the four-component method, while being 30 times faster. The IODKH-IOSO-MFSO methodology should pave the way toward computing larger and more general molecules beyond the four-component method limits.

Original languageEnglish
Pages (from-to)816-820
Number of pages5
JournalJournal of Computational Chemistry
Volume36
Issue number11
DOIs
Publication statusPublished - 2015 Apr 30

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Keywords

  • isotope fractionation
  • nuclear volume effect
  • relativistic quantum chemistry
  • two-component theory
  • uranium

ASJC Scopus subject areas

  • Chemistry(all)
  • Computational Mathematics

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