Theoretical characterization of the disilaethynyl anion (Si2H

The singlet-state potential energy surface of the disilaethynyl anion (Si2H−) has been investigated using ab initio self-consistent-field (SCF), configuration interaction with single and double excitations (CISD), coupled cluster with single and double excitations (CCSD), and CCSD with perturbative triple excitations [CCSD(T)] levels of theory with large basis sets. Four stationary points [cyclic (monobridged) 1A1 (C2v), linear 1Σ+ (C∞v), bent 1A′ (Cs), and quasilinear 1A′ (Cs) structures] were located with the correlated wave functions, while only two stationary points [cyclic (monobridged) 1A1 (C2v) and linear 1Σ+ (C∞v) structures] were found with the SCF method. The cyclic structure (C2v) is predicted to be the global minimum at all levels of theory. The linear structure (C∞v) is found to be a transition state between the two quasilinear structures (Cs) at the correlated levels of theory, while the SCF linear structure is predicted to be a transition state between the two cyclic structures. The quasili...