# Equation-of-Motion Coupled-Cluster Variants in Combination with Perturbative Triples Corrections in Strong Magnetic Fields

## TL;DR

This paper introduces new computational methods to study electronic states of atoms and molecules in strong magnetic fields, aiding in the analysis of white dwarf star spectra.

## Contribution

The implementation of EOM-CCSD variants and non-perturbative triples corrections in strong magnetic fields is novel.

## Key findings

- The methods enable the investigation of IPs and EAs in strong magnetic fields for first and second row elements.
- Electronic structure calculations for Na, Mg, and Ca in magnetic fields help assign metal lines in white dwarf stars.
- Electronic excitations of CH in magnetic fields are studied for applications in WD star atmospheres.

## Abstract

In this paper, we report on the implementation of the
EOM spin-flip
(SF), ionization-potential (IP), and electron-affinity (EA) coupled
cluster singles doubles (CCSD) methods for atoms and molecules in
strong magnetic fields for energies as well as one-electron properties.
Moreover, non-perturbative triples corrections using the EOM-CCSD­(T)­(a)*
scheme were implemented in the finite-field framework for the EE,
SF, IP, and EA variants. These developments allow access to a large
variety of electronic states as well as the investigation of IPs and
EAs in a strong magnetic field. The last two indicate the relative
stability of the different oxidation states of elements. The increased
flexibility to target challenging electronic states and access to
the electronic states of the anion and cation are important for the
assignment of spectra from strongly magnetic white dwarf (WD) stars.
Here, we investigate the development of IPs and EAs in the presence
of a magnetic field for the elements of the first and second rows
of the periodic table. In addition, we study the development of the
electronic structure of Na, Mg, and Ca in an increasingly strong magnetic
field that aided in the assignment of metal lines in a magnetic WD.
Lastly, we investigate the electronic excitations of CH in different
magnetic-field orientations and strengths, a molecule that has been
found in the atmospheres of WD stars.