Thermodynamic properties of germanium/carbon microclusters.

Theoretical studies on the Ge_nC_m (n=1,2; m=1–3) microclusters have been performed using the state of the art calculations. Several alternative structures of these clusters were studied to locate the lowest-energy isomers. It is observed that the structures of the complexes result from the competition between ionic Ge–C, conjugated covalent C–C, and metallic Ge–Ge bonds. The ionization of the molecules enhances the ionic character of the Ge–C bond and has significant structural consequences. Using theoretically determined partition functions, thermodynamic data are computed and experimental enthalpies are enhanced. The ab initio atomization energies of germanium carbides compare well with corrected experimental functions. The experimental appearance potentials are well reproduced by the theoretical ionization potentials. [ABSTRACT FROM AUTHOR]