Be(2)C monolayer with quasi-planar hexacoordinate carbons: a global minimum structure.

The design of new materials is an important subject in order to attain new properties and applications, and it is of particular interest when some peculiar topological properties such as reduced dimensionality and rule-breaking chemical bonding are involved. In this work, we designed a novel two-dimensional (2D) inorganic material, namely Be2 C monolayer, by comprehensive density functional theory (DFT) computations. In Be2 C monolayer, each carbon atom binds to six Be atoms in an almost planar fashion, forming a quasi-planar hexacoordinate carbon (phC) moiety. Be2 C monolayer has good stability and is the lowest-energy structure in 2D space confirmed by a global minima search based on the particle-swarm optimization (PSO) method. As a semiconductor with a direct medium band gap, Be2 C monolayer is promising for applications in electronics and optoelectronics.