Coupled-cluster theory for atoms and molecules in strong magnetic fields

TL;DR

This paper develops a complex coupled-cluster method incorporating gauge-including atomic orbitals to accurately study atoms and molecules in strong magnetic fields, addressing gauge-origin dependence and wave function complexity.

Contribution

It introduces a novel implementation of CC theory for magnetic fields, handling complex wave functions and gauge dependence, enabling accurate energy calculations.

Findings

Correlation energies vary with magnetic field strength.

Binding energies are significantly affected by magnetic fields.

The method provides reliable results for atoms and molecules in strong magnetic fields.

Abstract

An implementation of coupled-cluster (CC) theory to treat atoms and molecules in finite magnetic fields is presented. The main challenges stem from the magnetic-field dependence in the Hamiltonian, or, more precisely, the appearance of the angular momentum operator, due to which the wave function becomes complex and which introduces a gauge-origin dependence. For this reason, an implementation of a complex CC code is required together with the use of gauge-including atomic orbitals to ensure gauge-origin independence. Results of coupled-cluster singles--doubles--perturbative-triples (CCSD(T)) calculations are presented for atoms and molecules with a focus on the dependence of correlation and binding energies on the magnetic field.