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Journals and Conferences
Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package,… (More)
A summary of the technical advances that are incorporated in the fourth major release of the Q-CHEM quantum chemistry program is provided, covering approximately the last seven years. These include developments in density functional theory methods and algorithms, nuclear magnetic resonance (NMR) property evaluation, coupled cluster and perturbation… (More)
The majority of calculations of molecular vibrational spectra are based on the harmonic approximation but are compared (usually after empirical scaling) with experimental anharmonic frequencies. Any agreement that is observed in such cases must be attributable to fortuitous cancellation of errors and it would certainly be preferable to develop a more… (More)
We present a new systematic algorithm, energy-directed tree search (EDTS), for exploring the conformational space of molecules. The algorithm has been designed to reliably locate the global minimum (or, in the worst case, a structure within 4 kJ mol(-1) of this species) at a fraction of the cost of a full conformational search, and in this way extend the… (More)
High-level ab initio molecular orbital theory calculations have been used to calculate the rate coefficients and Arrhenius parameters for dimer models of the propagation steps for the free-radical homopolymerization of methyl acrylate and vinyl acetate at 298.15 K. Gas-phase Arrhenius parameters, as calculated under the hindered rotormodel, showed large… (More)
The protonation state of the deazaflavin dependent nitroreductase (Ddn) enzyme bound cofactor F420 was investigated using UV-visible spectroscopy and computational simulations. The reduced cofactor F420H2 was determined to be present in its deprotonated state in the holoenzyme form. The mechanistic implications of these findings are discussed.
Competitive kinetic experiments utilising free radical carbonylation chemistry provide a first estimate for the rate constant for 6-endo cyclization of the 6-aza-7-ethyl-5-hexenoyl radical of (4.8 +/- 2.4) x 10(6) s(-1) at 90 degrees C in benzene, in good agreement with ONIOM-G3(MP2)-CC+COSMO-RS calculations (6.8 x 10(6) s(-1)).
Free energies for the homolysis of the NO-C and N-OC bonds were compared for a large number of alkoxyamines at 298 and 393 K, both in the gas phase and in toluene solution. On this basis, the scope of the N-OC homolysis side reaction in nitroxide-mediated polymerization was determined. It was found that the free energies of NO-C and N-OC homolysis are not… (More)
Ab initio molecular orbital theory has been used to study and explain the effects of chain length on the addition– fragmentation equilibrium constant in reversible addition–fragmentation chain transfer (RAFT) polymerization. New data is presented for azobisisobutyronitrile-initiated t-butyl dithiobenzoate-mediated polymerization of methyl methacrylate, and… (More)
The performance of a variety of DFT functionals (BLYP, PBE, B3LYP, B3P86, KMLYP, B1B95, MPWPW91, MPW1B95, BB1K, MPW1K, MPWB1K, and BMK), together with the ab initio methods RHF, RMP2, and G3(MP2)-RAD, and with ONIOM methods based on combinations of these procedures, is examined for calculating the enthalpies of a range of radical reactions. The systems… (More)