On modelling the interaction of CO on the MgO(100) surface

Abstract

In this work we discuss the interaction of an adsorbate on an ionic surface taking as representative example CO on a perfect MgO(100) surface. The main goal is to investigate the different contributions to the interaction and how to model them by using a finite cluster model. To this end we use three different ab initio Hartree-Fock approaches. First, we discuss the convergence properties of the array of point charges used to simulate the Madelung potential. Next, we use large cluster models to show that there is an oscillatory behavior of the interaction energy. We show that rather large clusters are needed to avoid such oscillations. Also, we discuss how to represent these large clusters by using model potentials and compare the results with those obtained from periodic Hartree-Fock calculations. The interaction of CO on MgO is found to be weak and of electrostatic origin, with no noticeable chemical contributions.