Molecules for materials:: Germanium hydride neutrals and anions.: Molecular structures, electron affinities, and thermochemistry of GeHn/GeH-n (n=0-4) and Ge2Hn/Ge2H-n (n=0-6)

The GeHn (n = 0-4) and Ge2Hn (n = 0-6) systems have been studied systematically by five different density functional methods. The basis sets employed are of double-zeta plus polarization quality with additional s- and p-type diffuse functions, labeled DZP+ +. For each compound plausible energetically low-lying structures were optimized. The methods used have been calibrated against a comprehensive tabulation of experimental electron affinities (Chemical Reviews 102, 231, 2002). The geometries predicted in this work include yet unknown anionic species, such as Ge2H-, Ge2H2-, Ge2H3-, Ge2H4-, and Ge2H5-. In general, the BHLYP method predicts the geometries closest to the few available experimental structures. A number of structures rather different from the analogous well-characterized hydrocarbon radicals and anions are predicted. For example, a vinylidene-like GeGeH2- structure is the global minimum of Ge2H2-. For neutral Ge2H4, a methylcarbene-like HGe-GeH3 is neally degenerate with the trans-bent H2Ge=GeH2 structure. For the Ge2H4 anion, the methylcarbene-like system is the global minimum. The three different neutral-anion energy differences reported in this research are: the adiabatic electron affinity (EA(ad)), the vertical electron affinity (EA(vert)), and the vertical detachment energy (VDE). For this family of molecules the B3LYP method appears to predict the most reliable electron affinities. The adiabatic electron affinities after the ZPVE correction are predicted to be 2.02 (Ge-2), 2.05 (Ge2H) 1.25 (Ge2H2), 2.09 (Ge2H3), 1.71 (Ge2H4), 2.17 (Ge2H5), and -0.02 (Ge2H6) eV. We also reported the dissociation energies for the GeHn (n = 1-4) and Ge2Hn (n = 1-6) systems, as well as those for their anionic counterparts. Our theoretical predictions provide strong motivation for the further experimental study of these important germanium hydrides. (C) 2002 Wiley Periodicals, Inc.