GE2H2 - A MOLECULE WITH A LOW-LYING MONOBRIDGED EQUILIBRIUM GEOMETRY

Recent experimental and theoretical studies reporting remarkable monobridged structures for Si2H2, Al2H2, and Ga2H2 have motivated us to re-investigate the singlet potential energy surface of Ge2H2 using the self-consistent-field (SCF), single and double excitation configuration interaction (CISD), and single and double excitation coupled cluster (CCSD) methods in conjunction with a double-zeta plus polarization basis set (DZP). In addition to the dibridged (or butterfly) ground state and the low-lying vinylidene-like minimum reported earlier by Grev and DeLeeuw, our study predicts the existence of a monobridged isomer, which is characterized as a minimum by means of harmonic vibrational frequency analyses. Relative energies of the above structures were also predicted with use of the coupled cluster single, double, and (perturbative) triple excitation method (CCSD(T)), which employed a triple-zeta plus polarization basis set augmented with a set of f functions on the germanium atoms (TZP+f). Final energetic predictions suggest that the monobridged structure is the second most stable isomer of Ge2H2, lying 8.9 kcal mol-1 above the butterfly ground state and 2.1 kcal mol-1 below the branched (vinylidene-like) minimum.