Discovering novel VC1-x compounds through hybrid first-principles and evolutionary algorithms

摘要

VC1-x compounds, known as ultra-high temperature ceramics, are able to maintain stability in a range of chemical compositions. Herein, using evolutionary algorithm USPEX, we performed a global search for potentially stable VC1-x compounds. We have discovered two stable compounds (P3(1)12-V6C5 and Pnnm-V2C) and a number of near-ground-state compounds (Fm (3) over barm-VC, P4(3)32-V8C7, P (1) over bar -V5C4, I (4) over bar 3m-V4C3 CMCM-V3C2, and Cmcm-V3C). The stable Pnnm-V2C is a new structure with lower total energy than experimentally reported alpha-V2C. Based on these stable and meta-stable VC1-x compounds, we have systemically investigated their structures, mechanical properties, and chemical bonding. We found that Cmcm-V3C2 and Cmcm-V3C display different arrangements of vanadium from other VC1-x compounds. We suggest that such rearrangement of vanadium are able to enhance mechanical strength. Most of VC1-x compounds possess very good mechanical properties, indicating that they have potential to be utilized for structural applications. (C) 2016 Elsevier Ltd. All rights reserved.