Structure and Stability of M−H₂ Complexes

Abstract

The potential stability of van der Waals complexes M−H2 (M = Li, Be, B, C, Na, Mg, Al, Si) is assessed using quadratic configuration interaction and large basis sets. It is found that the alkali metals and alkaline earths form very weak complexes in their ground states, but much stronger complexes in their (p) excited states. The elements B, Al, C, and Si form both linear (C∞v) and perpendicular (C2v) complexes, with greater thermodynamic stability in the latter arrangements. The complexes formed by C are likely to be kinetically unstable, and the same may be the case for Si. On the other hand, the complexes formed by B and Al are predicted to be quite stable. Disciplines Chemistry CommentsReprinted (adapted) ReceiVed: June 20, 1995; In Final Form: September 6, 1995 X The potential stability of van der Waals complexes M-H 2 (M ) Li, Be, B, C, Na, Mg, Al, Si) is assessed using quadratic configuration interaction and large basis sets. It is found that the alkali metals and alkaline earths form very weak complexes in their ground states, but much stronger complexes in their (p) excited states. The elements B, Al, C, and Si form both linear (C ∞V ) and perpendicular (C 2V ) complexes, with greater thermodynamic stability in the latter arrangements. The complexes formed by C are likely to be kinetically unstable, and the same may be the case for Si. On the other hand, the complexes formed by B and Al are predicted to be quite stable.

Quenching of Li ( 2 P) by H 2 : potential energy surfaces, conical intersection seam, and diabatic bases

“…1. The results are in good accord with the recent study of Chaban and Gordon [19] who report a collinear van der Waals minimum at R CG vm 9X845Y 1X402Y 0 with an energy i 1 2 A H R CG vm 15 cm À1 . Also found was a van der Waals-like saddle point on the groundstate PES for the perpendicular con®guration R vts 10X66Y 1X4011Y 90 with i 1 2 A H R vts 5X6 cm À1 , again in good accord with the results of Gordon and Chaban, R CG vts 10X204Y 1X402Y 90 with i 1 2 A H R CG vts 9 cm À1 .…”

“…e 1X05 eV, that is about 0.8 eV below i 2 2 A H R asym (see Fig. 1), in good accord with 1.13 eV found by Hobza and Schleyer [15], 1.063 eV found by Boldyrev and Simons [21], and 1.054 eV reported by Chaban and Gordon [19]. No other minima were found on this PES.…”

“…Using the method of interacting correlated fragments, Konowalow [18] determined the dissociation energy of the complex to be in the range 13±18 cm À1 . Chaban and Gordon [19] carried out a thorough study of the van der Waals Li H 2 complex at the MP4SDQ and QCISD(T) levels with the augmented correlation-consistent valence-triple-zeta (aug-cc-pVTZ) basis set for H and the cc-pVTZ basis for Li. They found a complex with g Iv symmetry stable by about 15±17 cm À1 X In the present work the electronic structure aspects of reaction (1) are considered.…”

Computational Studies of the Ground and Excited State Potentials of DMSO and H2SO: Relevance to Photostereomutation

“…It was found that the 1 A′ states wave function converged only with the second-order SCF (SOSCF) method. 45 The full Newton-Raphson orbital improvement (FULLNR) method was used to obtain the singlet A′′ states, both triplet A′ and A′′ states, and all C 2V excited states. 46 …”

Interfacing Electronic Structure Theory with Dynamics

“…We have recently discovered cyclic isomers on the lowest singlet and triplet PES of N 3 F. 51 The geometrical parameters of these stationary points and barrier heights for isomerization and dissociation were determined at the multiconfigurational self-consistent field (MCSCF) 29 level of theory using the standard 6-31G(d) basis set. 39 Relative isomer energies and barrier heights were recalculated using multireference secondorder perturbation theory (CASPT2) 45 and multireference configuration interaction (MRCI), 5 with larger 6-311G(d) and 6-311G(2d) basis sets.…”