Ab initio study of Be (0001) surface thermal expansion

We present a first-principles study, within the quasiharmonic approximation, of the thermal expansion of Be (0001) surface. The free energy is obtained from full vibrational dispersions computed by density-functional perturbation theory. Our calculation describes very well the thermal expansion in the bull; and has been checked against first-principles molecular dynamics simulations in the surface case. We do not fmd the large thermal expansion recently observed experimentally and we argue that the morphology of the actual surface could be less ideal than assumed.