Prediction of Ta₂C‐Type Vacancy‐Layered Structures in the Ternary Hf–Ta–C System

Abstract

Herein, the vacancy‐ordered structures in the ternary Hf–Ta–C system are investigated by the first‐principles method and evolutionary algorithms. In addition to the rocket‐salt structure, two Ta2C‐type structures, HfTa2C2 and Hf2Ta2C3, are predicted, and their space groups are determined to be R‐3m. In these two structures, the vacancy layers are formed perpendicular to the c‐axis, and the vacancies occupy the [Ta6] octahedral interstices. Furthermore, the electronic properties of HfTa2C2 and Hf2Ta2C3, such as the electron‐localization function, density of state, band structure, partial charge density, and charge–density distribution, are calculated and analyzed. It is shown in the results that the localized electrons locate in the layered vacancies originating from the Ta atoms and that they form localized metallic bonds. Therefore, HfTa2C2 and Hf2Ta2C3 exhibit higher elastic modulus and Vickers hardness than the rock‐salt structure.