Methodologies to analyze surface bonding properties using parametric and density functional methods

Abstract

This work presents two general methodologies to calculate bond, adsorption energy (BAE) between surface and adsorbate using parametric quantum (PQM) and density functional (DFM)Methods. The first one corresponds to the bond partition energy technique that is directly applied, to PQMs by using energy partition approach and considering diatomic and monoatomic energy changes. The second methodology to evaluate BAE, as well as for PQMs and DFMs, is by means of the following equation: BAE = Ead - △Es- △E a, where Eadsis the adsorption energy and △E sand△Eacorrespond to energy changes in the surface and substrate due to adsorption, respectively. Applications to radical adsorption:H°,CH2°, CH3°on performed on grafitic grain model,using a polyaromatic hydrocarbon (PAH), such as coronene. The methods employed, are a PQM (CATIVIC program) and DFMs (GAUSSIAN and DMol software packages).Results show that Eadsis completely different of BAE, because of distortion of surface and adsorbate. There is a strong destabilization in the region adjacent to the adsorption site and stabilization in the rest of the surface. Two terms for BAEb)that corresponds to direct bonding interaction (BAEb) and other to long range ones, due to electrostatic interaction (BAEe) Owing to the imortant effects of bond strength adsorbate-surface interaction, results suggest that BAE is fundamental for understanding bond activation in adsorbate and surface, cooperative effects, diffusion, reaction, and desorption process. In general, similar results were found for both CATIVIC and DFMs, by using the second methodology. © 2009 Wiley Periodicals, Inc.