Structural and electronic analysis of β-Mo2C doped with transition metals based on electronic structure calculations.

Abstract

A systematic density functional study (DFT) is carried out to assess the stability of orthorhombic molybdenum carbide (β-Mo2C) doped with 3d, 4d, and 5d transition metal (TM) elements. The doping energy trends are rationalized from electronic descriptors such as the work function (ϕ), d-band center (εd), first ionization energy (IE1) and projected density of states (PDOS). From an energetic point of view, a low ϕ of the doped system and a low IE1 of the doping TM favor doping. On the contrary, a high first ionization energy of the doping TM results in unfavorable β-Mo2C doping. The density of states analysis is consistent with the doping energy trends. In particular, the TM atoms in the middle of the transition series enhance the stability through the strong hybridization of metal d orbitals and C 2p orbitals. This promotes the electron delocalization of the d orbitals of TMs around the Fermi level, favoring the thermodynamic stability of the doped β-Mo2C. This comprehensive study can help experimentalists identify plausible doped transition metal carbide systems beyond the β-Mo2C case study presented here by analyzing the key electronic aspects of doping elements.

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