Pair potential description on phase stability variations in close-packed polytypism

Abstract

We report an extensive analysis on phase stability variations in close-packed (CP) polytypes, including hexagonal CP (hcp or 2H), face-centered cubic (fcc or 3C), and double hexagonal CP (dhcp or 4H) arrangements. This analysis involves the systematic development of interatomic pair potentials and the derivation of computational phase diagrams in the feature space of corresponding potential profiles. We focus on the following key components of interaction model: the reach distance of atomic interactions and perturbative long-range interactions reminiscent of Friedel oscillations which often lead to long-range interaction decay in crystalline materials. The computational experiments reveal that the perturbative interactions reflecting atomic local structures in CP polytypes, essentially diversify the polytypism in the phase diagrams. Using the pure La system with the 4H ground state, we also provide detailed procedures for creating practical pair potentials that approximately reproduce the energetics and physical properties deduced through the first-principles calculations. Graphical abstract