Ab initio calculation of molecule-surface binding: methyl halides on GaAs(110) surfaces

Large scale ab initio cluster calculations are used to examine the binding of methyl halides to the (110) surface of GaAs. The results of the calculations are compared with recent experimental measurements of the binding energies. Three approaches to electron correlation are examined: density functional methods utilizing the generalized gradient approximations (specifically, the BLYP functional) or adiabatic connection formulas (B3LYP), and local MP2 methods which intrinsically eliminate basis set superposition errors. The BLYP calculations are found to underestimate the binding substantially; the B3LYP and LMP2 results are: closer to experiment but are still underestimates. Structures optimized at the B3LYP level are in good agreement with experimental geometries. The results are encouraging with regard to the ability of suitable quantum chemical methods to accurately treat the dative bonding important for a reliable description of molecule-surface interactions. (C) 1997 Elsevier Science B.V.