On chemical bonding and helium distribution in hcp beryllium

The electron densities of states and spatial distribution of electron density in the system hcp beryllium-helium were investigated by means of ab-initio methods of simulation. It was found that contrary to predictions of the “jelly” model, the energetically more favorable configuration is that where a helium atom is located at the most restricted position, on a triangular face of two adjacent tetrahedrons, and where the charge density of electrons is maximal. It is established that this occurs due to hybridization of electron states of helium and nearest beryllium atom. The helium binding energy is about 5.6 eV. The spatial distribution of the charge density is investigated in details. Calculation of solution energy of helium in hcp beryllium was performed. The helium location at lattice sites in different interstitial positions and in divacancy complexes were considered. It is found that helium implemented into hcp beryllium favors formation of divacancies.