Importance of bond exchange in MnC structural stability and half-metallic ferromagnetism: a comprehensive density functional benchmark study

Abstract

Recently, a first successful synthesis of the unknown bulk manganese monocarbide (MnC) has been reported. Suggested as a potential superhard material, the compound is found to crystallize in the zincblende (B3) structure. In the present work, we report an exhaustive density functional investigation on structural, electronic and magnetic properties of MnC, using different levels of exchange-correlation approximations. We show that SCAN meta-GGA and PBE0r hybrid functional outperform GGA-PBEsol, HSE06 hybrid functional and the mean field DFT+$U$+$V$; in predicting correctly the experimental zincblende structure as the groundstate one. It is demonstrated that the bond exchange plays a crucial role in this stabilization. At theoretical equilibrium, hybrid functionals (PBE0r and HSE06) lead to a metallic behavior of MnC. Semilocal ones (PBEsol and SCAN) and mean field DFT+$U$+$V$, however, predict two opposite kinds of half-metallic ferromagnetism; opening a debate on the origin and the nature this behavior. If the latter is confirmed experimentally, MnC could be for importance as a spintronic material.

14 pages, 7 figures

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