Molecular frame dipole moment of diatomic molecules within relativistic coupled‐cluster framework: A comparative study of expectation value versus energy derivative approach

Abstract

The ground state molecular frame dipole moments of alkaline earth metal monofluorides and Group ІІB-monohydrides have been computed using two analytic methods, namely the Z-vector technique and the linear expectation value method within the four-component relativistic coupled cluster singles and doubles framework. We have compared our results with the experimentally measured permanent dipole moments wherever available. It is found that the Z-vector method, which is an energy-derivative approach predicts the molecular permanent dipole moment more accurately than the linear expectation value approach in DZ and TZ quality basis set.Further, our study shows that the high-energy virtual spinors seem to have almost no influence on the permanent dipole moment whereas the core electron correlation slightly affects this molecular property.

Permanent electric dipole moment of diatomic molecules using relativistic extended-coupled-cluster method

“…Thus, we can say that ECC can be a suitable method to estimate molecular-frame electric dipole moment of diatomics under consideration. It is noteworthy that Pal and co-workers [2,3,13] studied the PDMs of a number of open-shell diatomic molecules using fully relativistic coupled-cluster-based approaches such as Z-vector and linear expectation-value methods and also investigated the effects of basis set size, virtual spinors and hamiltonians on accurate prediction of PDM, which indicates that an increase in the basis set size and correlation space improves accuracy of the computed results. However, we have limited ourselves to calculate the desired molecular property at triple-zeta quality basis set with 500 a.u.…”

“…Unitary coupled-cluster (UCC), expectationvalue coupled-cluster (XCC) and extended-coupled-cluster (ECC) approaches are three major variational forms of the CC theory found in literature. In recent times, a number of coupled-cluster-based methods have been extended to relativistic framework and these relativistic ab initio methods were used to compute energy and energy-derivatives of many-electron systems [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Molecular-frame electric dipole moment, also known as the permanent electric dipole moment (PDM), is an important first-order static property.…”

“…In recent times, a number of studies have been reported on the computation of PDMs of these molecules using various electronic structure methods [25][26][27][28]. Relativistic coupled-cluster-based methods were also employed to accurately predict the PDMs of diatomic molecules and the effects of electron-correlation and relativistic motion of electrons in computing molecular PDMs were explored [13][14][15][16][17][18]. We, in this article, employ a variational many-body method− the relativistic extended-coupled-cluster method within singles and doubles approximation to compute the PDMs of a few moderately heavy alkaline-earth metal halides and hydrides.…”

Relativistic coupled-cluster study of SrF for low-energy precision tests of fundamental physics

“…The LE method within the relativistic single-reference coupled-cluster framework was successfully employed to compute a number of molecular properties by some of the present authors [23,29,30,49].…”

“…1. We restrain ourselves from a detailed discussion of the MDM results of SrF since a couple of studies of the same have already been conducted by Pal and coworkers using the same methodology [46,49]. The DHF result for the MDM decreases as the basis set size increases from DZ (basis A to E) to TZ (F basis), however, the MDM value increases at basis G (TZ) due to the augmentation of diffuse functions on the F-atom.…”