The 2H, 1T, and their distorted structures are known as prototype structures of AB2 monolayers. Here, we study a puckered structure that is truncated from the (110) surface of fluorite-type materials. 53 fluorite-type materials are investigated based on first-principles approach. The formation energy calculations indicate that seven systems form the puckered structure in the monolayer limit, while other systems form either 1T, 2H, or distorted 1T structures. The puckered structures of PbF2, PRh2, and Ga2Au exhibit negative Poisson's ratio (NPR) in the out-of-plane direction. An analytical model for the NPR is derived. The surface energy calculations predict the appearance of NPR.
Cite
@article{arxiv.2404.09394,
title = {Fluorite-type materials in the monolayer limit},
author = {Shota Ono and Ravinder Pawar},
journal= {arXiv preprint arXiv:2404.09394},
year = {2024}
}