Theoretical Study of the Electronic Structures of HfB2(0001)-X (X = Li−Ne) Surfaces

Abstract

The electronic structures of HfB2(0001)-X (X = Li through Ne) surfaces have been calculated using density functional theory (DFT) and properties such as adsorption sites, adsorption energies, oscillation energies, and electron densities have been obtained. Experimentally, the HfB2(0001) clean surface is terminated by a (1 × 1) Hf layer, and our calculation revealed that all adsorbed elements except neon have the highest stability on the threefold hollow site. Among these elements, oxygen has the largest adsorption energy and nitrogen the largest oscillation energy, although boron, carbon, and oxygen have nearly the same value as nitrogen. The electron density indicates that all of the elements except lithium and neon form covalent bonds with hafnium on the surface. Nitrogen has the largest electric charge, and it was discovered that the quantity of charge for a given adatom is determined by the difference in electronegativity between the adatom and Hf atom and by the valence of the adatom.