Lithium halide monolayers: Structural, electronic and optical properties by first principles study

• Structural optimizing represents that unlike graphene-like structures, the cubic face structure is more favorable for alkali halide 2D structures.
• Nonbonding electron pairs cause a planar buckling for all compounds.
• Electronic calculations show that all compounds have an indirect energy gap.
• All compounds are optically transparent in the visible spectrum range.

Using first principle study, we investigate the structural, electronic and optical properties of lithium halide monolayers (LiF, LiCl, LiBr). In contrast to graphene and other graphene-like structures that form hexagonal rings in plane, these compounds can form and stabilize in cubic shape interestingly. The type of band structure in these insulators is identified as indirect type and ionic nature of their bonds are illustrated as well. The optical properties demonstrate extremely transparent feature for them as a result of wide band gap in the visible range; also their electron transitions are indicated for achieving a better vision on the absorption mechanism in these kinds of monolayers.

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