A local density functional investigation of the clean and the hydrogen covered Li(001) surface

A detailed density functional theory study on periodic slab models of the clean and the hydrogen covered Li(001) surface is presented to corroborate recent experiments on atomic hydrogen adsorption at lithium surfaces. Questions of model convergence as well as the bonding mechanism in the adsorption system are investigated. Several tools are employed to analyze the self-consistently determined electronic structure of the Li(001) and H Li(001) slab models, among them one-particle core level shifts, overlap populations and density difference maps. To quantify the charge separation within the ionic surface layer formed in the H Li(001) adsorption system, the topological atom approach and a recently developed technique uniquely based on the electrostatic potential above the surface are used. Lithium is found to behave to some extent like a covalent solid rather than an s electron metal, while the adsorption system H Li at full monolayer coverage is best characterized by an insulator-metal interface.