Calculation of hyperfine structure constants of small molecules using Z-vector method in the relativistic coupled-cluster framework

Abstract

The Z-vector method in the relativistic coupled-cluster framework is employed to calculate the parallel and perpendicular components of the magnetic hyperfine structure constant of a few small alkaline earth hydrides (BeH, MgH, and CaH) and fluorides (MgF and CaF). We have compared our Z-vector results with the values calculated by the extended coupled-cluster (ECC) method reported in Phys. Rev. A 91 022512 (2015). All these results are compared with the available experimental values. The Z-vector results are found to be in better agreement with the experimental values than those of the ECC values.

Hyperfine Structure Constants on the Relativistic Coupled Cluster Level with Associated Uncertainties

“…28 The finite field approach is particularly useful in the framework of the CC theory, since the formulation of expectation values is cumbersome due to the complicated form of the wave function. That said, several implementations exist for calculation of CC expectation values; the recent relativistic examples are the extended CC method (ECC), 26 the Z-vector CC method, 29 and analytic gradients approach. 30 An advantage of using the finite field method is that no truncation of the CC expansion is necessary (which is the case for the ECC method for example) and that it allows inclusion of the perturbative triple excitations without additional complications.…”

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

“…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.…”