材料期刊网

The coordination-dependent force field of Tersoff for covalently bonded Si has been used to calculate the cleavage force as a function of interplanar separation and hence to estimate surface energies. This force field is already fitted to density functional results. The relation to bond-breaking and electron correlation will be emphasized. Finnis-Sinclair-type many-body potentials have then been used to treat some d-electron metals. In particular, results for cleavage force in bcc Fe will be presented, and also some calculations as two perfectly planar Fe surfaces are `rubbed together' at different interplanar separations. Finally, lattice dynamical models for the steady-state propagation of a screw dislocation, and then of a crack, will be used, again within a bond-breaking type of force field. For the screw dislocation propagation, a solitary wave equation is shown to follow in the ‘almost continuum' limit. Energy radiated by phonons as the dislocation moves can thereby be calculated.