Current Research

Our research comprises both general theoretical development and diverse computational applications of molecular quantum mechanics. Work in the Allen group ranges from the solution of chemical problems using computations as a tool of discovery, to the abstract development of theoretical formalisms and mathematical algorithms, to the programming of practical, state-of-the-art computer codes.  In principle, the exactness and universal applicability of the Schrödinger/Dirac equation allows all branches of chemistry to be investigated by molecular quantum mechanics.  Accordingly, the research in the Allen group spans many areas, with a common theme of rigorous, high accuracy predictions based on definitive wave function methods. The following is an illustrative but not exhaustive list of topics on which papers have been published within the past few years.

Chemical applications: (1) Combustion chemistry and energy research – alkyl oxidation, soot formation, and aromatic pyrolysis mechanisms; (2) Matrix isolation and theoretical characterization of novel carbenes; (3) Tunneling dynamics of hydrogen transfer; (4) Secondary structures of peptides and proteins via NMR chemical-shielding anisotropy (CSA); (5) Definitive structures of building blocks of biomolecules; (6) Structure-reactivity relationships in SN2 reactions; (7) Small carbon and silicon clusters; (8) Large-amplitude vibrational averaging of optical rotation; (9) Cosmological habitable zone for the fine structure constant and the electron/proton mass ratio.

Theoretical methods: (1) Multireference coupled cluster theory; (2) Explicitly-correlated electronic structure theory; (3) Focal-point schemes for achieving ab initio limits of thermochemistry and spectroscopy; (4) Anharmonic force fields and vibrational analyses of polyatomic molecules; (5) Two-electron basis set incompleteness diagnostics; (6) High-order many-body perturbation series – convergence properties, resummation methods, and Møller-Plesset critical points.

Selected Publications

Gerbig, D. ; Reisenauer, H. P. ; Wu, C. - H. ; Ley, D. ; Allen, W. D. ; Schreiner, P. R. Phenylhydroxycarbene. Journal of the American Chemical Society 2010, 132, 7273–7275.
Miller, J. A. ; Klippenstein, S. J. ; Georgievskii, Y. ; Harding, L. B. ; Allen, W. D. ; Simmonett, A. C. Reactions between Resonance-Stabilized Radicals: Propargyl + Allyl. Journal of Physical Chemistry A 2010, 114, 4881–4890.
Feng, H. ; Allen, W. D. The Problematic C2H4 + F2 Reaction Barrier. Journal of Chemical Physics 2010, 132, 094304: 1–8.
Mátyus, E. ; Fábri, C. ; Szidarovszky, T. ; Czakó, G. ; Allen, W. D. ; Császár, A. G. Assigning Quantum Labels to Variationally Computed Rotational-Vibrational Eigenstates of Polyatomic Molecules. Journal of Chemical Physics 2010, 133, 034113: 1–14.
Wheeler, S. E. ; Houk, K. N. ; v. Schleyer, P. R. ; Allen, W. D. A Hierarchy of Homodesmotic Reactions for Thermochemistry. Journal of the American Chemical Society 2009, 131, 2547–2560.
Evangelista, F. A. ; Simmonett, A. C. ; Schaefer III, H. F. ; Mukherjee, D. ; Allen, W. D. A Companion Perturbation Theory for State-Specific Multireference Coupled Cluster Methods. Physical Chemistry Chemical Physics 2009, 11, 4728–4741.
Schreiner, P. R. ; Reisenauer, H. P. ; Pickard IV, F. C. ; Simmonett, A. C. ; Allen, W. D. ; Mátyus, E. ; Császár, A. G. Capture of Hydroxymethylene and Its Fast Disappearance through Tunnelling. Nature 2008, 453, 906-909.
Crawford, D. T. ; Sherrill, D. C. ; Valeev, E. F. ; Fermann, J. T. ; King, R. A. ; Leininger, M. L. ; Brown, S. T. ; Janssen, C. L. ; Seidl, E. T. ; Kenny, J. P. ; Allen, W. D. PSI3: An Open-Source Ab Initio Electronic Structure Package. Journal of Computational Chemistry 2007, 28, 1610–1616.
Czinki, E. ; Császár, A. G. ; Magyarfalvi, G. ; Schreiner, P. R. ; Allen, W. D. Secondary Structures of Peptides and Proteins via NMR Chemical-Shielding Anisotropy (CSA) Parameters. Journal of the American Chemical Society 2007, 129, 1568–1577.
Sergeev, A. V. ; Goodson, D. Z. ; Wheeler, S. E. ; Allen, W. D. On the Nature of the Møller-Plesset Critical Point. Journal of Chemical Physics 2005, 123, 064105: 1–11.