Comparison of Voronoi Tessellation‐Derived and Molecular Dynamics‐Derived Atomistic Models of Polycrystalline Titania: A Computational Study of Structures, Band Structures, and Mechanical Properties

Abstract

Grain boundaries (GB) affect properties of polycrystalline ceramics, including mechanical and electronic properties. While often individual postulated GBs are considered in atomistic models, a distribution of GBs present in real ceramics should be accounted for. An often‐used method to build polycrystalline models is geometry‐based Voronoi tessellation. With it, random grain orientations generally obtain in atomistic models of GBs with non‐physically high Miller index grain surfaces. Recently, models of polycrystalline rutile TiO2 were constructed with molecular dynamics (MD) using computational heat treatment, a procedurally nature‐like approach resulting in a distribution of GBs dominated by low‐index surfaces. It is important to understand the similarities and differences in GB‐affected properties with MD‐ and Voronoi tessellation‐based models for informed selection of an appropriate model for specific applications. Such a comparison is presented. Structural properties and the effect of grainy structures on mechanical properties and band structure are compared. High‐index surfaces prevalent in Voronoi structures lead to the formation of amorphous interlayers, and fracture stress is lower than with MD‐based structures. Band structures of GBs are analyzed in large‐scale electronic structure calculations. It is found that while low‐index surfaces do not result in trap states, high‐index surfaces and amorphous interlayers may introduce such states.