An extension of the tersoff-hamann model for a molecule on a graphite support: STM-image construction

Abstract

A method is proposed for the theoretical construction of STM images of adsorbates on a graphite support. Tunnel current is taken to be proportional to the local density of graphite electronic states perturbed by the interaction with the adsorbed molecule. The coefficients of mixing of the graphite states with the adsorbate MOs are found by first-order perturbation theory, using the CNDO-S2 method to calculate the adsorbate electronic structure together with analytical expressions for the graphite states. The long-distance behavior of adsorbate MOs is taken into account by means of energy-dependent MO asymptotics. As an example of the implications of this technique, the theoretical STM images of benzene and butane molecules on a graphite surface are presented and discussed.