Ab initio study of beryllium surfaces with different hydrogen coverages

The effect of hydrogen concentration on principal hexagonal close-packed beryllium surfaces (basal, prismatic type I and II, pyramidal type I and II) at 0 K was studied with the help of ab initio methods. The configurations with critical hydrogen coverage were revealed. Relaxation of outermost atomic layers at critical coverage drastically differs from that found for clean beryllium surfaces. The presence of hydrogen atoms significantly changes the energy of all studied beryllium surfaces except for prismatic type II plane. Influence of hydrogen concentration on equilibrium shape of hydrogen covered voids was investigated by means of construction of Wulff polyhedra. In addition we generalized Gibbs-Wulff approach for accounting of different hydrogen coverages at crystallographic non-equivalent surfaces and temperature effect. The results of the construction were compared with classical Gibbs-Wulff approach as well as the available experimental data on ion or neutron irradiation at elevated temperatures.

147