三元Hf-C-N体系的空位有序结构及其力学性质和电子性质的第一性原理研究  

First-principles study of vacancy ordered structures,mechanical properties and electronic properties of ternary Hf-C-N system

作　　者：彭军辉 Tikhonov Evgenii Peng Jun-Hui;Tikhonov Evgenii(International Center for Materials Discovery,School of Materials Science and Engineering,Northwestern Polytechnical University,Xi’an 710072,China;Department of Materials Engineering,Taiyuan Institute of Technology,Taiyuan 030008,China)

机构地区：[1]西北工业大学材料学院,材料发现国际中心,西安710072 [2]太原工业学院材料工程系,太原030008

出　　处：《物理学报》2021年第21期229-239,共11页Acta Physica Sinica

基　　金：外国人才引进与学术交流项目(批准号:B08040)资助的课题。

摘　　要：采用第一性原理方法,研究了三元Hf-C-N体系的空位有序结构及其力学性质和电子性质.首先采用第一性原理和进化算法,预测得到8种可能存在的热力学稳定的Hf-C-N空位有序结构;这些结构都具有岩盐结构,与实验发现的无序固溶体的结构类型一致.本文的预测结果证明了Hf-C-N空位化合物能够以有序结构形式存在,空位与C,N原子都位于[Hf6]八面体间隙,这一结构特点与Hf C_x的相同.然后采用第一性原理方法,计算了Hf-C-N空位有序结构的力学性质,发现除C∶N=1∶4外,相同C/N下,随着空位浓度的增大,Hf-C-N的体模量、剪切模量、弹性模量、Pugh比、维氏硬度等降低;而Hf6CN4(空位浓度为1/6)的维氏硬度高于Hf_5CN_4(无空位),表现出空位硬化现象.最后,计算了Hf-C-N空位有序结构的态密度和晶体轨道哈密顿分布,发现其具有强共价性和金属性;且随着空位浓度增大,总体键强减弱,因而模量减小.The thermal-mechanical properties of transition metal carbonitrides can be affected by the concentration and ordering of vacancies besides the C/N atomic ratio.However,there are few reports on the vacancy ordered structure of ternary transition metal carbonitrides.In the present paper,the first-principles method is used to study the vacancy ordered structures,mechanical properties,electronic properties and the effect of vacancies on the ternary Hf-C-N system.Firstly,the crystal structures of Hf-C-N system is examined by the first-principles and evolutionary algorithms implemented in USPEX under ambient pressure,and eight thermodynamical stable vacancy ordered structures are found,each of which has a rock-salt structure,and is also dynamical and mechanical stable,which are verified by the calculations of their phonon dispersion curves and elastic constants.The vacancies are occupied at the[Hf6]octahedral interstices,which replace the positions of non-metal atoms.Their crystallographic data such as space group,lattice constants are also predicted.To the best of our knowledge,there is no report on the Hf-C-N vacancy ordered structures and these structures investigated here in this work are all found for the first time.Then their mechanical properties are calculated.The Hf-C-N vacancy ordered structures all have very high bulk,shear and elastic modulus and hardness.It is found that except for C∶N=1∶4,for the Hf-C-N system with the same C/N ratio the moduli,Vickers hardness values,and Pugh’s ratios decrease with the increase of the concentration of vacancy.However,the Vickers hardness of Hf6CN4(the concentration of vacancy is equal to 1/6)is higher than that of Hf5CN4(no vacancy),that is so-called vacancy hardening.Finally,the electronic density of states and the crystal orbital Hamilton populations are calculated.The chemical bonding of Hf-C-N vacancy ordered structure is analyzed,which is a mixture of covalence and metallic and is similar to that of binary transition metal carbides and nitrides.With the increa

关 键 词：Hf-C-N空位有序结构 空位 维氏硬度 第一性原理方法 

分 类 号：O469[理学—凝聚态物理]