Application of electronic structure and transition state theory: Reaction of hydrogen with silicon radicals

Abstract

AbstractThe reaction of molecular hydrogen with silicon radicals is investigated through direct dynamics calculations. Previous studies of this reaction with E′ centers vary in their description of the reaction thermodynamics and kinetics. A survey of methods is conducted to illuminate the best method for describing these properties. This is achieved via a similar reaction with a silyl radical, in which both the forward and reverse directions are considered, discussed in terms of theory, basis, and the importance of tunneling corrections. The methods studied include Hartree–Fock (SCF), two density functionals (B3LYP and MPW1K), Møller–Plesset second‐order perturbation (MP2), and coupled‐cluster singles and doubles (CCSD) with a variety of all electron basis sets ranging from 6‐31G to aug‐cc‐pVTZ. Two methods are identified as good candidates: a density functional theory (DFT) method (MPW1K) and a dual‐level method including MP2, and CCSD theories. These methods yield rate constants that agree within one order of magnitude of experiment and activation energies within 1 kcal/mol over the 293–683 K temperature range. The B3LYP and SCF methods do not perform as well and are discounted early. Basis sets that perform well are found to include diffuse and polarizing functions on all atoms, including hydrogen. These include the 6‐31++G** and aug‐cc‐pVDZ basis sets. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006