Effect of Reconstruction on the Electronic Free Energy of a Simple Model of Transition Metals

Abstract

We present the results of theoretical studies of the change in free energy associated with surface reconstruction for one simple model of transition metals. We study the dependence of the free energy on reconstruction for a semi-infinte simple cubic lattice with one tight-binding Wannier orbital per unit cell. For this model, we compare the free energy of the unreconstructed surface with that when the surface is deformed into a 2\ifmmode\times\else\texttimes\fi{}1 configuration. The effect of the distortion is introduced into the model by allowing the overlap integrals to vary with interatomic separation. We find that this particular mode of reconstruction always lowers the electronic free energy, with maximum effect when the band is half-filled. The physical origin of the changes in electronic density of states with reconstruction is discussed. The variation with temperature of the given gain in the electronic free energy is also studied.