STRUCTURES AND PROPERTIES OF GEH5+ IONS AS REVEALED BY POST-HARTREE-FOCK CALCULATIONS

Ab initio electronic structure calculations at the SCF, MP2, CISD, and CCSD(T) levels in conjunction with basis set of at least triple zeta plus polarization (TZP) quality were applied to characterize the potential energy surface of GeH5+ ion. Molecular structures and harmonic vibrational frequencies were calculated for the six possible structures at the SCF and MP2 levels. The lowest energy conformer was further optimized and characterized using the CISD approximation. The most stable structure has a C-s symmetry with the H-2 unit bound sideways to the GeH3+ fragment, similar to the group IV analogue, SiH5+. The C-s transition structure for rotation of the H-2 moiety has virtually identical energy with the global minimum structure, and lying 31.37 kcal/mol (CCSD(T)/TZP+f) above the minimum is the C-2v transition structure for hydrogen scrambling (pseudorotation). Our best estimate of the dissociation energy for GeH5+ taking into account the zero-point energy (ZPE) is 9.66 kcal/mol compared to 10.3 kcal/mol predicted for the analogous SiH5+ system.