Lattice instability of V_2AlC at high pressure  

作　　者：YANG ZeJin LIU Qiang LI Jin WANG Zhao GUO AiMin LINGHU RongFeng CHENG XinLu YANG XiangDong 

机构地区：[1]School of Physics,Zhejiang University of Technology [2]School of Physics,Chongqing University of Technology [3]College of Material and Chemical Engineering,Hainan Provincial Key Laboratory of Research on Utilization of Si-Zr-Ti Resources,Hainan University [4]Institute of Physics,Chinese Academy of Sciences [5]School of Physics,Guizhou Normal College [6]Institute of Atomic and Molecular Physics,Sichuan University

出　　处：《Science China(Physics,Mechanics & Astronomy)》2013年第5期916-924,共9页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos.10974139,10964002,11104247 and 11176020);the Provincial Natural Science Foundation of Guizhou (Grant Nos.[2009]2066 and TZJF-2008-42);the Provincial Natural Science Foundation of Hainan (Grant No.110001);the Provincial Natural Science Foundation of Chong Qing(Grant No.CSTCcstc2011jja90002);the Provincial Natural Science Foundation of Zhejiang (Grant No.Y201121807)

摘　　要：We investigate the elastic and thermodynamic properties of nanolaminate VzA1C by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. The elastic constants revealed the structural instability at about 500 and 732 GPa. Furthermore, elastic constants C44 reached its maximum at about 550 GPa, dif- fering with the other four C^1, G2, C13 and 6＂33 constants. The Poisson＇s ratio investigations demonstrated that a higher ionic or weaker covalent contribution in intra-atomic bonding and the degree of ionicity increases with pressure. The G/B and B]C44 investigations revealed that VzAIC is brittle and the brittleness decreases with pressure. Also, we found that V2A1C is elastic anisotropic materials and the degree of anisotropy rapidly rises with pressure. Study on Debye temperature and Grtineisen pa- rameter observed weak temperature and strong pressure responses, whereas the sensitive dependence in the thermal expansion coefficient and Helmholtz free energy are clearly seen.We investigate the elastic and thermodynamic properties of nanolaminate V2 AlC by using the ab initio pseudopotential total energy method. The axial compressibility shows that the c axis is always stiffer than a axis. The elastic constants revealed the structural instability at about 500 and 732 GPa. Furthermore, elastic constants C44 reached its maximum at about 550 GPa, differing with the other four C11 , C12 , C13 and C33 constants. The Poisson's ratio investigations demonstrated that a higher ionic or weaker covalent contribution in intra-atomic bonding and the degree of ionicity increases with pressure. The G/B and B/C44 investigations revealed that V2 AlC is brittle and the brittleness decreases with pressure. Also, we found that V2 AlC is elastic anisotropic materials and the degree of anisotropy rapidly rises with pressure. Study on Debye temperature and Grüneisen parameter observed weak temperature and strong pressure responses, whereas the sensitive dependence in the thermal expansion coefficient and Helmholtz free energy are clearly seen.

关 键 词：ELASTICITY thermodynamicity first principles 

分 类 号：O482.1[理学—固体物理]