Theoretical properties of a 3‐layer film of LiBeH 3

The linear combinations of Gaussian‐type orbitals‐fitting function ( LCGTO ‐ FF ) technique has been used to calculate the binding energy and electronic band structure of a 3‐atom‐thick film extracted from bulk LiBeH 3 in the cubic perovskite structure. The film is composed of an interior layer of LiH sandwiched between two exterior layers of BeH 2 , i.e., there are eight atoms per unit cell (1 Li, 2 Be, and 5 H). The calculated cubic lattice parameter for the 3‐layer (a = 5.74 au) lies roughly midway between the previously published theoretical lattice parameters for a BeH 2 monolayer (5.51 au) and bulk LiBeH 3 in the cubic perovskite structure (5.89 au). The 3‐layer film is predicted to be a semimetal (i.e., zero‐gap semiconductor), unlike both bulk LiBeH 3 which is predicted to be a semiconductor, and monolayer BeH 2 , which is predicted to be a good metal. The metallic nature of the 3‐layer is due to a Be surface state that cuts across the other valence bands of the film, in good agreement with an earlier prediction that cubic perovskite LiBeH 3 cleaved to expose a BeH 2 layer would provide a metallic surface on an insulating substrate. The fact that the density of states goes to zero at the Fermi level is a direct result of the symmetries of the one‐electron states.