An empirical many-body potential energy function for modelling ytterbium

An empirical potential energy function, comprising two- and three-body terms, has been derived for the rare-earth element ytterbium, by fitting parameters to the phonon dispersion curves, elastic constants, lattice energy and lattice distance of the face-centred-cubic (fcc) phase of Yb. This potential reproduces the structural data for fee Yb, including the negative Cauchy pressure, and correctly accounts for the metastable bcc phase. We predict the bcc phonon dispersion curves (not yet available in the literature) and the activation energy for the Bain transformation between the fee and bcc phases. The surface energies and relaxations of the high-symmetry surfaces of fee Yb ((111), (100) and (110)) are calculated for the first time. Furthermore, we predict that the (110) surface of Yb is stable with respect to the 1 x 2 'missing-row' reconstruction.