Structures and transition states of Ge2CH2.

In this study a systematic theoretical inves- tigation of Ge2CH2 is carried out. The singlet potential energy surface (PES) was explored using state-of-the-art theoretical methods including self-consistent field (SCF), coupled cluster theory incorporating single and double excitation (CCSD), perturbative triple (CCSD(T)) and full triples (CCSDT) with perturbative quadruple (Q), together with a variety of correlation-consistent polarized valence basis sets cc-pVXZ (where X = D, T, and Q). A total of eleven stationary points have been located on the Ge2CH2 singlet ground state PES. Among them, seven structures are minima (1S�7S), two are transition states (TS1 and TS2), and two are second-order saddle points (SSP1 and SSP2). The global minimum is predicted to be an exotic hydrogen-bridged structure 1S. The energy ordering of the seven minima (in kcal mol �1 ) obtained from focal point analysis using the extrapolation to complete basis set (CBS) limit with zero point vibrational energy (ZPVE), core correlation, diagonal BornOppenheimer (DBOC) and relativistic correction is 1S (0.0) < 2S (17.2) < 3S (18.3) < 4S (31.7) < 5S (39.9) < 6S (58.1) < 7S (82.1).