Mg3X2 (X = C, Si) monolayer in a honeycomb-kagome lattice: A global minimum structure

Two stable Two-dimensional (2D) material with a hexagonal honeycomb structure, i.e., the Mg3X2 (X = C, Si) monolayer have been predicted using a newly developed particle swarm optimization algorithm based on first-principles calculations. We found that the Mg3X2 exhibit a Dirac feature which arises from the p z orbitals of Mg and X atoms under the nonmagnetic (NM) state. The Dirac cone are not affected by stress strains along both the x and y directions. After considering the magnetic configuration, the ground state of Mg3X2 is antiferromagnetic (AFM) state. This magnetic configuration breaks the Dirac feature and causes a sizeable band gap in Mg3X2 monolayer. The newly predicted Mg3X2 is both mechanically and dynamically stable, implying its experimentally synthetic feasibility. The results are beneficial to this new 2D material in applications and providing a feasible strategy for 2D materials design. (C) 2018 Elsevier B.V. All rights reserved.