First Principles Study the Stability and Mechanical Properties of M3B2(M=V, Nb and Ta) Compounds

摘要:

采用基于密度泛函理论（DFT）的第一性原理对过渡金属硼化物M3B2（M=V, Nb, Ta）的稳定性、化学键、弹性常数、硬度以及徳拜温度进行计算和预测。这些硼化物的结构已经经过优化，得到的晶格常数与实验值相符。通过得到的这些硼化物的结合能和生成焓，确定了这些硼化物具有稳定的结构。通过计算，还得到了M3B2（M=V, Nb, Ta）的弹性常数、相关模量及泊松比。

Abstract:

The first principles calculations based on density functional theory (DFT) were performed to investigate the stability, the chemical bonding, the elastic constants, the hardness and the Debye temperatures of M3B2 (M=V, Nb and Ta). The structures of these borides were optimized, and the lattice parameters are in good agreement with the experimental values. The calculated cohesive energy and the formation enthalpy indicate that they are thermodynamically stable structure. The mechanical properties including elastic constants Cij, bulk modulus, young’s modulus, shear modulus and Poisson’s ratio were calculated. The Debye temperatures of M3B2 (M= V, Nb and Ta) were calculated. The results show that the values of M3B2 range from 299 to 526 K. The hardness of M-B bonds was calculated using a semi empirical hardness theory.