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Updated: May 9, 2026

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

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Published on: April 8, 2020

Relativistic unitary coupled-cluster method for ground-state molecular properties.

Kamal Majee¹, Somesh Chamoli¹, Malaya K Nayak^2,3

¹Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.

The Journal of Chemical Physics

|May 8, 2026

Summary

This summary is machine-generated.

We introduce a new relativistic coupled-cluster method for heavy elements. The non-perturbative approach accurately calculates properties like dipole moments, outperforming older methods.

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Area of Science:

Quantum Chemistry
Relativistic Calculations
Atomic Physics

Background:

Coupled-cluster methods are essential for accurate electronic structure calculations.
Relativistic effects become significant for heavy elements, influencing their properties.
Calculating first-order properties requires sophisticated theoretical frameworks.

Purpose of the Study:

To develop and apply a relativistic unitary coupled-cluster expectation-value approach.
To compute ground-state properties of heavy-element systems.
To assess the performance of perturbative and non-perturbative formulations.

Main Methods:

Relativistic unitary coupled-cluster (UCC) theory.
Expectation-value approach for first-order properties.
Perturbative and non-perturbative commutator-based formulations.
Calculations of permanent dipole moment, magnetic hyperfine structure constant, and electric field gradient.

Main Results:

The non-perturbative commutator-based UCC approach showed superior agreement with experimental data and the UCC Z-vector method.
Both perturbative and non-perturbative methods were applied to calculate key properties.
The non-perturbative method, truncated at singles and doubles, demonstrated improved accuracy.

Conclusions:

The non-perturbative relativistic UCC expectation-value method is a reliable tool for heavy-element systems.
This approach offers better accuracy than perturbative variants due to improved relaxation effect treatment.
The findings provide a more accurate way to compute properties of heavy elements.