Significance of Non-Linear Terms in the Relativistic Coupled-Cluster Theory in the Determination of Molecular Properties

V Srinivasa Prasannaa,Minori Abe,Bhanu P Das,Bijaya K Sahoo

doi:10.3390/sym12050811

V Srinivasa Prasannaa, Minori Abe + Show 2 more

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https://doi.org/10.3390/sym12050811

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Journal: Symmetry	Publication Date: May 13, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: Tokyo Institute of Technology

Abstract

The relativistic coupled-cluster (RCC) theory has been applied recently to a number of heavy molecules to determine their properties very accurately. Since it demands large computational resources, the method is often approximated to single and double excitations (RCCSD method). The effective electric fields ( E e f f ) and molecular permanent electric dipole moments (PDMs) of SrF, BaF, and mercury monohalides (HgX with X = F, Cl, Br, and I) molecules are of immense interest for probing fundamental physics. In our earlier calculations of E e f f and PDMs for the above molecules, we neglected the non-linear terms in the property evaluation expression of the RCCSD method. In this work, we demonstrate the roles of these terms in determining the above quantities and their computational time scalability with the number of processors of a computer. We also compare our results with previous calculations that employed variants of RCC theory, as well as other many-body methods and available experimental values.

Highlights

The coupled-cluster (CC) theory is considered to be the gold standard of electronic structure calculations in atoms and molecules [1,2]
We chose HgF as a representative molecule and performed FFRCCSD calculations with a quadruple zeta (QZ) basis, and we found that its effective electric field was 110.87 GV/cm, which was lesser than the nLERCCSD value by 2.5 percent
We investigated the contributions from the non-linear terms of the property evaluating the expression of the relativistic coupled-cluster theory in the determination of permanent electric dipole moments and effective electric field due to the electron electric dipole moment of SrF, BaF, and mercury monohalide (HgX with X = F, Cl, Br, and I) molecules

Summary

Introduction

The coupled-cluster (CC) theory is considered to be the gold standard of electronic structure calculations in atoms and molecules [1,2]. It owes the title to its ability to capture electron correlation effects to a much better extent than other well-known many-body approaches such as configuration interaction (CI) [3], at a given level of truncation. This feature has led to accurate calculations of many properties in both the atomic and molecular systems (for example, see [4,5]). The molecular PDM is a very interesting property, and it plays a role in the sensitivity of an eEDM experiment through the polarizing factor [8,9].

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