Mechanical And Electronic Propetries Of5d Transition Metal Dinitrides By First-Principles

At present super hard materials are still limited to diamond and cubic BN. Due to it’sextremely vital significance in the basic sciences and industrial applications, designing andexploring super hard materials naturally become a concern subject that has lastingsignificance. This article investigated the mechanical properties and electronic structure of5dtransition metal dinitrides TMN₂（TM=Hf、Ta、W、Re、Os、Ir、Pt） by frst-principles, in orderto find new favorable candidate of super hard material.In this work, the Castep module of Material Studio4.4software package, which wasbased on density functional theory, was applied to calculate the structural, mechanical andelectronic properties of5d transition metal dinitrides. Firstly, the formation energy and elasticconstants were calculated to judge the thermal stability and mechanical stability according tothe corresponding criterions. Secondly，the lattice constant, volume, bulk modulus, shearmodulus, Poisson’s ratio and Young’s modulus of the dinitrides were calculated，and theresults indicated that the trend of the hardness was firstly increased and then decreased fromHfN₂to PtN₂. The most advantageous one in hardness was OsN₂.Thirdly, the electronic structure of the dinitrides was analysised to reveal the nature ofthe trend of hardness. The strength of covalent bond was estimated by analyzing the bondlength and the G/B value. The conductivity, hybridization of orbital and the filling of bondingstates and anti-bonding states were studied according to the density of states and partialdensity of states.