Electronic origin of shearing in M2AC (M = Ti,V,Cr,A = Al,Ga)
Electronic origin of shearing in M2AC (M = Ti,V,Cr,A = Al,Ga)
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DOI：
10.1088/0953-8984/17/46/001
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发表时间：
2005-11
期刊：
影响因子：
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通讯作者：
Zhimei Sun;D. Music;R. Ahuja;J. Schneider
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文献类型：
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作者：
Zhimei Sun;D. Music;R. Ahuja;J. Schneider
本文用从头算方法研究了M_2AC（空间群P_63/mmc，原型Cr_2AlC）中的剪切行为，其中M为Ti，V和Cr，A为Al和Ga。这些化合物可以被描述为MC和A的交错层。V取代Ti后，C_（44）增加了24.3%。进一步增加过渡金属价电子浓度，通过由Cr取代V，导致c44降低2.2%。这c44与价电子浓度依赖的电子起源可以理解通过分析分解的能带结构：在附近的费米能级，我们发现两种类型的dd键。一个有助于剪切（t2 g +eg对称性或MC-MC耦合），另一个不起作用（例如对称性）。我们提供的证据表明，填充的过渡金属dd键的t2 g +eg对称状态可能是负责的c44的行为。所提出的结果使得能够定制M2 AC相的剪切性质。
We have studied shearing in M2AC (space group P63/mmc, prototype Cr2AlC), where M is Ti, V and Cr, and A is Al and Ga, using ab initio calculations. These compounds can be described as interleaved layers of MC and A. As Ti in Ti2AlC is substituted by V, c44 increases by 24.3%. Increasing the transition metal valence electron concentration further, through a substitution of V by Cr, results in 2.2% decrease of c44. The electronic origin of this c44 versus valence electron concentration dependence may be understood by analysing the decomposed band structure: in the vicinity of the Fermi level, we find two types of dd bonding. One contributes to shearing (t2g+eg symmetry or MC–MC coupling) and the other does not (eg symmetry). We provide evidence that filling of the transition metal dd bonding states with the t2g+eg symmetry may be responsible for the behaviour of c44. The results presented enable tailoring of the shear properties of M2AC phases.