Perspective: Coupled cluster theory for atoms and molecules in strong magnetic fields

Abstract

In this perspective, the theoretical treatment of atoms and molecules in strong magnetic fields is discussed. As this is a rather unexplored field, accurate predictions from theory are essential. This is particularly important in the context of astrophysics for the interpretation of observational spectra from white-dwarf stars that can exhibit magnetic fields up to about 1 B0 (≈ 235,000 T). A theoretical treatment beyond the pertubation limit requires methods that can deal with finite magnetic fields. Results obtained using coupled cluster (CC) as well as equation-of-motion CC theory are presented with a focus on a discussion of the so-called “perpendicular paramagnetic bonding mechanism” as well as on the influence of electron correlation on total and binding energies. Additionally, the performance of functionals in current density functional theory is discussed. As exact results are completely unknown, highly accurate benchmarks are essential to assess the quality of density functional theory results. Finally, an outlook on future theoretical developments is given.