Electronic and elastic correlations in AlB2-type two-dimensional hexagonal MBenes

Abstract

Abstract With the advent of MXenes as two-dimensional (2D) materials beyond graphene, non carbonic 2D materials analogically referred as MBenes have significantly attracted researchers’ attention. Such 2D MBenes remains largely unexplored. Here, we systematically investigate electronic and elastic properties of 2D transition metal (TM) based AlB2-type hexagonal MBenes consisting of a honeycomb networked graphene like boron layer embedded with diverse TM atoms at center. First we determine the thermodynamic, dynamic, thermal, and mechanical stability of MBenes, considering a wide range of 3d, 4d, and 5d TM elements. Electronic and elastic calculations are performed for stable MBenes in order to parameterize and investigate the interdependence of properties. Elastic calculations predicts the brittle-ductile nature and bond character of MBenes while unraveling the in-plane auxetic behavior. Our electronic calculations predict the metallic band nature for 2D VB2, NbB2, TaB2, and WB2 along with previously reported dirac points in 2D TiB2, FeB2, ZrB2, and HfB2. The elastic and electronic calculations clearly indicates the non-directional metallic bonds and intrinsically ductile nature of 2D-FeB2 distinct from other MBenes. Subsequently we performed a covariance analysis to assess the correlation amongst the observables of interest and further establish the interdependence of the properties. Our calculations for elastic correlations also suggests that mechanical brittle-ductile nature and auxetic behavior of MBenes can be tuned by strain engineering of the elastic constants. Our results further suggests that strong correlations between Poisson ratio and d state electrons can be utilized to tune the auxetic behavior by careful doping of the materials. Our work demonstrates the weak elastic-electronic correlations, suggesting that the strain engineering can be utilized for the tailored behavior of MBenes for practical applications. Thus, our systematic analysis of the mechano-elastic and electronic properties of 2D hexagonal MBenes and their correlations advance our understandings of emergent 2D family.