Theoretical Study of Carbon K‐Edge Energy‐Loss Near‐Edge Structure Spectra in the Ordered Mo2TiAlC2 MAX and Mo2TiC2 MXene

Abstract

By means of density functional theory, the energy‐loss near‐edge structure (ELNES) of carbon K‐edge of Mo2TiAlC2 and corresponding MoTiC2 Mxene at orientational‐independent condition is dealt with. Compared to the MAX (M is transition metal, A is an elment from group 13–16, X is C or N) phase, the energy separations increase between the main spectral features at the C K edge of Mo2TiC2 MXene owing to the structural change and decreased bond length. The dispersions of the C K edge in both systems are similar to p‐symmetry densities of states. It is indicated that the source of the first fine structure at the C 1s edge in both phases mainly comes from the electron transfer to px + py‐like character. The other fine structures result from the transition to hybridization of pz and px + py states with the prominent contribution of px + py‐like character. Moreover, the comparison of C K‐edge ELNES spectra in three Mo‐based compounds reveals that, ongoing from Mo2TiAlC2 to Mo2TiC2 and then to Mo2C, the energy position of the fine structures is shifted to higher energies (blueshifted), due to the quantum confinement effects and the change of the chemical environment around the excited carbon.