MC与$lt;i$gt;M$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;+1$lt;/sub$gt;$lt;i$gt;AC$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;$lt;/sub$gt;稳定性与电子特征的第一性原理研究

研究MC与M_n+1AC_n(M=Sc, Ti, V, Cr, Mn; A=Al, Si, P, S; n=1, 2, 3)结构的稳定性与电子特征有利于探究三元层状结构M_n+1AC_n稳定性的内在原因和设计新型M_n+1AC_n结构. 第一性原理计算研究表明, M-3d与C-2p轨道间的电子转移对MC与M_n+1AC_n 的形成焓有较大影响. 供电子能力较强的前过渡金属可以形成稳定的MC结构. 计算结果显示, MC结构是缺电子体系, 其趋向于与具有一定供电子能力的MA结构结合形成M_n+1AC_n. 与M₂PC和M₂SC 相比, M₂AlC和M₂SiC可以更为容易地被分离成二维 M₂C结构. 关键词： MAX相结构 第一性原理 电子结构 过渡金属碳化物

First-principles study on stability and electronic properties of MC and Mn+1ACn phases

Investigation of the stability and electronic properties of a series of MC compounds and classic MAX phases, M_n+1AC_n (M=Sc, Ti, V, Cr, and Mn; A=Al, Si, P, and S; n=1, 2, and 3), contributes to finding the intrinsic mechanism of the stability of M_n+1AC_n and to the design of new M_n+1AC_n phases. First-principles calculations show that the formation enthalpy of both MC and M_n+1AC_n is directly correlated with the charge transfer from M-3d to C-2s and 2p orbitals. Correspondingly, the early transition metals with high electron donation ability are able to form stable MC phases. Among the various MC phases, MC is found to be electron-deficient, which is thus favorable to react with electron-abundant MA to form M_n+1AC_n. Therefore, M₂AlC and M₂SiC can be more readily separated into two-dimensional M₂C structures, compared to M₂PC and M₂SC.
Keywords： MAX phases first-principles electronic structures transition metal carbides