Density functional theory and reduced density gradient investigations into HCN adsorption on the Co(100) and Co(110) surfaces

Thirteen kinds of adsorptions of HCN on the Co(100) and Co(110) surfaces at the 1/4 monolayer coverage and the reduced density gradients (RDGs) are investigated using the density functional theory. For Co(100), the adsorption energy of the most stable configuration (where HCN locates at the fourfold site with the C equivalent to N bonded to four Co atoms) is -1.836 eV. On Co(110), the bonding energy in the most favored adsorption configuration (in which HCN locates at the fourfold-long site) is -1.580 eV. The parallel adsorption configuration is energetically favored as compared with the perpendicular mode and the former weakens the strength of CE equivalent to N bond to a larger extent than the latter. Thus, the greater activation of the C equivalent to N bond may be found in the parallel configuration and hydrogenation reaction may be easier in the parallel configuration in which the adsorbed HCN becomes non-Mean The binding mechanism of HCN on the Co(100) and Co(110) surfaces is analyzed by Mulliken charge population and the density of states in HCN. The adsorption and metallic-bonding interactions are shown by the low density and low-gradient spike at negative values, while the low density and low-gradient region for the sterically crowded Co atoms remains at positive values indicating repulsion and steric effects.