Germylene Energetics: Electron Affinities and Singlet-Triplet Gaps of GeX2 and GeXY Species (X, Y = H, CH3, SiH3, GeH3, F, Cl, Br, I)

A systematic investigation of the GeX2 and GeXY species was carried out using the popular DFT functionals BLYP, B3LYP, and BHHLYP. Predicted are the singlet-triplet energy gaps and four types of neutral-anion separations: adiabatic electron affinity (EA(ad)), zero-point vibrational energy corrected EA(ad(ZPVE)), vertical electron affinity (EA(vert)), and vertical detachment energy. The basis sets used for all atoms in this work are of double-zeta plus polarization quality with additional s- and p-type diffuse functions denoted DZP++, except for iodine where the 6-311G(d,p) basis set is used. The geometries are fully optimized with each functional independently. Vibrational frequency analyses were performed to compute zero-point energy corrections and to determine the nature of the stationary points. The geometries and the relative energies are discussed and compared with the carbon and silicon analogues. The EA(ad(ZPVE)) values (eV) obtained with the B3LYP functional range from 0.62 eV [Ge(CH3)(2)] to 2.08 eV [Ge(GeH3)(2)]. These results compare satisfactorily with the few available experiments, but most are reported for the first time. Similarly, the predicted singlet-triplet energy separations range from 13.8 kcal mol(-1) [Ge(SiH3)(2)] to 85.0 kcal mol(-1) [GeF2]-Invariably, as one progresses down the periodic table C -> Si -> Ge, the "great divide" occurs between carbon and silicon.