### Abstract

We investigate the accuracy of two-component Douglas-Kroll-Hess (DKH) methods in calculations of the nuclear volume term (≡ lnK_{nv}) in the isotope fractionation coefficient. lnK_{nv} 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 lnK_{nv} values of uranium isotope exchange. In this work, we compared uranium reaction lnK_{nv} 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 lnK_{nv}. 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 language | English |
---|---|

Pages (from-to) | 816-820 |

Number of pages | 5 |

Journal | Journal of Computational Chemistry |

Volume | 36 |

Issue number | 11 |

DOIs | |

Publication status | Published - 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

### Cite this

*Journal of Computational Chemistry*,

*36*(11), 816-820. https://doi.org/10.1002/jcc.23858

**An ab initio study of nuclear volume effects for isotope fractionations using two-component relativistic methods.** / Nemoto, Keisuke; Abe, Minori; Seino, Junji; Hada, Masahiko.

Research output: Contribution to journal › Article

*Journal of Computational Chemistry*, vol. 36, no. 11, pp. 816-820. https://doi.org/10.1002/jcc.23858

}

TY - JOUR

T1 - An ab initio study of nuclear volume effects for isotope fractionations using two-component relativistic methods

AU - Nemoto, Keisuke

AU - Abe, Minori

AU - Seino, Junji

AU - Hada, Masahiko

PY - 2015/4/30

Y1 - 2015/4/30

N2 - 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.

AB - 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.

KW - isotope fractionation

KW - nuclear volume effect

KW - relativistic quantum chemistry

KW - two-component theory

KW - uranium

UR - http://www.scopus.com/inward/record.url?scp=84925664501&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84925664501&partnerID=8YFLogxK

U2 - 10.1002/jcc.23858

DO - 10.1002/jcc.23858

M3 - Article

AN - SCOPUS:84925664501

VL - 36

SP - 816

EP - 820

JO - Journal of Computational Chemistry

JF - Journal of Computational Chemistry

SN - 0192-8651

IS - 11

ER -