几种三元过渡金属碳化物弹性及电子结构的第一性原理研究

First-principles study of elastic and electronic properties of several ternary transition-metal carbides

基于密度泛函理论平面波方法研究了六方WC型RexW1-xC(x=1,0.25,0.75,0),Re0.5Os0.5C和Os0.5W0.5C的晶体结构、弹性和电子结构性质.研究发现Re0.25W0.75C晶体具有优异的弹性性能及稳定性,其剪切模量(312GPa)超过了所有其他实验合成和理论预测的5d过渡金属碳化物的相应值.电子态密度的结果表明它们均为金属性体系,费米面处较低的态密度值意味着Re0.25W0.75C具有更高的稳定性.对化合键密里根布居分析发现Re0.25W0.75C中Re—C键的共价性得到了很大提高,这种强的共价性是导致其具有优异弹性性能的关键因素.优异的弹性性能和高的稳定性说明Re0.25W0.75C是一种良好的高硬度材料.

With the first-principles density functional theory,based on ultra-soft psuedopotential method,the structure,elastic,and electronic structure properties of WC-type RexW1-x C（x = 1,0.25,0.75,0）,Re0.5 Os0.5 C,and Os0.5 W0.5 C were studied.It was found that the shear modulus of Re0.25 W0.75 C is higher than that of all synthesized and theoretically predicted 5d transition metal carbides.An analysis of Mulliken population of the bond between transition metal and C atom shows that the large shear modulus of Re0.25W0.75C is mainly due to the strong covalent Re—C interaction.The low value of the density of states on the Fermi level indicates the high stability of Re0.25 W0.75 C.The excellent elastic property and high stability suggest that hexagonal Re0.5W0.5C can be an ultra-hard material.We hope our calculations can stimulate the experimental research to synthesize it.