Theoretical study of Ge5H5+ isomers

The geometries of nine structures of Ge5H5+ have been optimized at the HF/3-21G(*) and the MP2/3-21G(*) levels of theory and their vibrational frequencies computed. Electron correlation errors in their energies are corrected up to the MP3 level using basis sets of triple-zeta plus polarization (TZP) quality. The singlet pentagerma [1,1,1] propellanyl cation is predicted to be, like Si5H5+, the global minimum on the Ge5H5+ potential surface. The pentagermavinylcyclopropenyl cation, the carbon analogue of which is the lowest energy structure of C5H5+, is least stable among the nine Ge5H5+ structures studied, lying 39.24 kcal mol−1 above the global minimum.