Pressure dependent structural, dynamical, mechanical and electronic properties of magnesium dicarbide

ABSTRACT

Magnesium dicarbide (MgC₂) at high pressure has been systematically investigated using the first-principle methods. Ten possible structures were studied and three of them (Cmcm, C2/m, P-3m1) were found to be dynamically and mechanically stable under the given pressure. The calculated formation enthalpies indicated that the Cmcm structure was thermodynamically unstable while the C2/m and P-3m1 structures were thermodynamically stable. The interesting thing was that the P-3m1 structure of MgC₂ could also be as potential hard materials owing to their Vickers hardness closing to 40 GPa with increasing pressure. The Cmcm and C2/m structures presented ductile behaviour while P-3m1 structure displayed brittle character. The elastic anisotropy of Young’s modulus E and shear modulus G became smaller with the increasing pressure, and the P-3m1 structure possessed a lower anisotropy in E and G than Cmcm and C2/m structures. The Cmcm and C2/m structures of MgC₂ had metallic characteristic; however, the P-3m1 structure of MgC₂ was semiconductor with an indirect band gap.

KEYWORDS:

• High pressure
• mechanical properties
• dynamical properties
• electronic properties

Acknowledgements

The authors would like to acknowledge the support from Dr X. Gonze and his coworkers for providing their version of ABINIT code.

Disclosure statement

No potential conflict of interest was reported by the author(s).