FORMATION ENERGIES OF METALLIC VOIDS, EDGES, AND STEPS - GENERALIZED LIQUID-DROP MODEL

The void formation energy is the work needed to create the curved surf ace of a void. For a spherical hole in a homogeneous metal (jellium or stabilized jellium), the void formation energy is calculated for larg e radii from the liquid-drop model (surface plus curvature terms), and for small radii from Perturbation theory. A Pade approximation is pro posed to link these limits. For radii greater than or equal to that of a single atom or monovacancy, the liquid-drop model is found to be us efully accurate. Moreover, the predicted monovacancy formation energie s for stabilized jellium agree reasonably well with those measured for simple metals. These results suggest a generalized liquid-drop model of possible high accuracy and explanatory value for the energetics of stable metal surfaces curved on the atomic scale (crystal faces, edges , corners, etc.). The bending energy per unit length for an edge at an gle theta is estimated to be gamma(pi - theta)/4, where gamma is the i ntrinsic curvature energy. The step energy is estimated as (n - 2 + pi /2)sigmad, where or is the intrinsic surface energy, n greater-than-or -equal-to 1 is the number of atomic layers at the step, and d is the l ayer height.