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The collinear reaction of Fe+ (4F) and Fe+ (6D) with H2 leading to FeH+ and H has been studied at the configuration interaction (CI) level of theory, using a relativistic pseudopotential approach. The 6D electronic state of Fe+ reacts with H2 through a very large energy barrier that slightly exceeds the endothermicity of the reaction. The 4F electronic state appears to be much more reactive than the 6D state, in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

The electronic states of FeH+ dissociating into Fe+ (6D) and H (2S) have been studied at the restricted open Hartree–Fock (ROHF) and configuration interaction (CI) level of theory, using a pseudopotential approach and considering or not relativistic effects. The ground state appears to be a 5Δ at the ROHF level but inclusion of correlation effects leads to a 5Π ground state. Nevertheless both states exhibit in all cases a near degeneracy. The calculated D0 is about 90% of the experimental value at the CI level whereas ROHF calculations account only for about 25% of the experimental dissociation energy. [ABSTRACT FROM AUTHOR]

Metropolis Monte Carlo simulations of hydration effects on rigid solutes characterizing the reactant, transition state (TS), and product for the rate limiting step of an acid catalized rearrangement of an a-acetylenic alcohol to α, β-unsaturated carbonyl compounds are calculated. The model compound corresponds to the protonated 3 methyl-but-1-yne-3-o1. The electronic structure and geometry of the corresponding species are determined with ab initio analytical gradient techniques; a 4-31G basis set has been used. Electrostatic and solute shape effects on samples having 125 MCY–water molecules at 300 K have been examined. Gurney’s model for ion–molecule interactions has been adopted. Although the solute–water potential used is very simple, the results on hydration energetics appear to be fairly reasonable. Solute shapes are found to play a significant role in producing differential solvation effects. Electrostrictive effects have been made evident by running MC simulations with fully uncharged solutes. A solvent activation barrier is detected. From the study of the TS solvation structures a possible incidence of ionic strength, counterion presence, and structure-making or breaking solutes can be conjectured. The structural features found for the solvation sheaths of reactant, TS, and product are in excellent agreement with the postulated molecular mechanism. [ABSTRACT FROM AUTHOR]

The electronic state of FeH dissociating into Fe (5D) and H (2S) have been studied at the restricted open Hartree–Fock (ROHF) and configuration interaction (CI) level of theory, using a relativistic pseudo-potential approach and including or not f functions in the basis set. The relative energies and spectroscopic properties obtained by us are in very good agreement with the experimental results found in the literature. In particular this work provides a new theoretical confirmation of a 4Δ electronic ground state for FeH. The effect of including or not f functions in the basis set is discussed. [ABSTRACT FROM AUTHOR]