The development of relativistic exact two-component (X2C) theory is briefly reviewed, with an emphasis on cost-effective treatments of relativistic two-electron contributions by means of model potential (MP) techniques and closely related atomic mean-field (AMF) approaches. The correct MP or AMF contribution to the electronic energy is elucidated. The performance of one-center approximations to relativistic two-electron contributions is carefully assessed using benchmark calculations of molecular properties.
@article{arxiv.2504.19479,
title = {Relativistic Two-Electron Contributions within Exact Two-Component Theory},
author = {Xubo Wang and Chaoqun Zhang and Junzi Liu and Lan Cheng},
journal= {arXiv preprint arXiv:2504.19479},
year = {2025}
}