MC与M_(n+1)AC_n稳定性与电子特征的第一性原理研究

First-principles study on stability and electronic properties of MC and M_(n+1)AC_n phases

研究M C与M n+1A C 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+1A C n稳定性的内在原因和设计新型M n+1A C 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M C与M n+1A C 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M C结构.计算结果显示,M C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+1A C n.与M2PC和M2SC相比,M2Al C和M2Si C可以更为容易地被分离成二维M2C结构.

Investigation of the stability and electronic properties of a series of MC compounds and classic MAX phases,Mn＋1ACn（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 Mn＋1ACn and to the design of new Mn＋1ACn phases. First-principles calculations show that the formation enthalpy of both MC and Mn＋1ACn 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 Mn＋1ACn. Therefore, M2 Al C and M2 Si C can be more readily separated into two-dimensional M2 C structures, compared to M2 PC and M2 SC.