EFFECTIVE CORE POTENTIAL MODELING OF GROUP IVA-GROUP IVB CHEMICAL-VAPOR-DEPOSITION

An effective core potential study of a model chemical vapor deposition (CVD) reaction is reported. Compounds studied are those in which a Group IVA (E = C, Si, Ge, Sn) main group element is directly bonded to a Group IVB (M = Ti, Zr, Hf) transition metal. Model reactants (H(3)M-EH(3)) possess Group IVA-Group IVB single bonds while products (H(2)M = EH(2), formed by H-2 elimination from reactants) have Group IVA-Group IVB multiple bonds. The main findings of this research are as follows: First, a single-determinant (RHF) description is appropriate for singly bonded Group IVA-Group IVB complexes. Agreement between experimental and calculated M-E single-bond lengths is very good at all levels studied. Second, electron correlation is of much greater importance for describing the ME pi bond than the ME sigma bond. Third, analysis of calculated double-to-single bond ratios (R(double)/R(single)) suggest that pi-bonding remains nearly constant over the entire series of compounds studied and is weaker than in the main group-main group analogs, suggesting a reason for the lack of reported examples with a Group IVA-Group IVB double bound. Fourth, barriers to elimination of H-2 from H(3)M-EH(3) show two significant trends. We propose that the trends as a function of transition metal (Ti < Zr < Hf) and main group element (C > Si > Ge > Sn) are due to trends in M-H and E-H bond energies. (C) 1995 John Wiley and Sons, Inc.