Dr. L. William Poirier

Principal Research Interests

• Quantum Dynamics of Chemical Reactions and Nanomaterials
• Theoretical and Computational Methods (quantum trajectory methods, wavelets, massive parallelization)

Professor Poirier's research group is concerned with the development and application of new methods for performing accurate quantum dynamics calculations for molecular systems. These calculations encompass rovibrational spectroscopy (especially highly excited states), reactive scattering of molecules in the gas phase and in nanomaterials, and resonance phenomena (energies, widths, phase shifts). Applications of interest include hydrogen storage in carbon nanomaterials, dynamics of rare gas clusters, thermal rate constants pertinent to environmental chemical kinetics, and mass-independent fractionation of SO2 photodissociation products as a proxy for the Archaen Earth atmosphere.

The methods development research is motivated by the inadequacy of conventional numerical techniques for dealing with large molecules, insofar as accurate, quantum dynamics calculations are concerned. Traditionally, the computational effort required scales exponentially with problem size, as a result of which such calculations have traditionally been limited to systems with four or fewer atoms. Dr. Poirier's group is exploring a variety of new approaches that improve the computational efficiency by orders of magnitude, thereby making it possible to handle a much larger class of systems than has heretofore been realized. The quantum trajectory approach, inspired by Bohmian mechanics, incorporates quantum effects into classical-like trajectory simulations. Symmetrized Weyl-Heisenberg wavelets defeat exponential scaling in basis set methods, and have been applied to Taylor-expanded-potential systems with up to 27 dimensions, and adapted for massively parallel computing platforms. Traditional iterative discrete variable representation methods have also been adapted for massively parallel computers, with up to tens of thousands of cores.

Representative Publications

• "On neglecting Coriolis and related couplings in rovibrational spectroscopy: considerations of symmetry, accuracy, and simplicity," J. Phys. Chem. Lett. (2019, submitted).
• "Communication: Adiabatic quantum trajectory capture for cold and ultra-cold chemical reactions," Y. Scribano, G. Parlant, and B. Poirier, J. Chem. Phys., 149, 021101 (2018).
• "Large Scale Exact Quantum Dynamics Calculations: Using phase space to truncate the basis effectively," B. Poirier, invited contribution, special issue in memory of John C. Light, Adv. Chem. Phys., 163, 245-271 (2018).
• "Final State Resolved Quantum Predissociation Dynamics of SO2(C̃1B2) and Its Isotopomers via a Crossing with a Singlet Repulsive State," C. Xie, B. Jiang, J. Klos, P. Kumar, M. H. Alexander, B. Poirier, and H. Guo, J. Phys. Chem. A, 121 (26), 4930-4938 (2017)
• "First-principles C̃ band absorption spectra of SO2 and its isotopologues," B. Jiang, P. Kumar, J. Klos, M. H. Alexander, B. Poirier, and H. Guo, J. Chem. Phys., 146 (15), 154305 (2017).
• "One Million Quantum States of Benzene," T. Halverson, B. Poirier, invited contribution in special issue. J. Phys. Chem. A, 119, 12417-12433 (2015)
• "The Many Interacting Worlds Approach to Quantum Mechanics", A Commentary on "Quantum Phenomena Modelled by Interactions Between Many Classical Worlds", B. Poirier, Phys. Rev. X 4, 040002 (2014)
• “NASA/NSF Summary Report from Workshop on: Mass-Independent Fractionation of Sulfur Isotopes: Carriers and Sources” S. D. Domagal-Goldman, B. Poirier, and B. Wing,(2012) https://astrobiology.nasa.gov/
• "Classical-like Trajectory Simulations for Accurate Computation of Quantum Reactive Scattering Probabilities," G. Parlant, Y.-C. Ou, K. Park and B. Poirier, invited contribution, lead article, special issue to honor Jean-Claude Rayez, Comput. Theoret. Chem. 990 3-17(2012)
• "Communication: Quantum Mechanics Without Wavefunctions," J. Schiff and B. Poirier, J. Chem. Phys., 136 (3), 031102 (2012). [Number One Most Read JCP Article For January 2012; among top seven for February and March 2012].
• "Rovibrational Bound States of Neon Trimer: Quantum dynamical calculation of all eigenstate energy levels and wavefunctions," B. Yang, W. Chen, and B. Poirier, J. Chem. Phys., 135(9), 094306 (2011) (17 pages).
• "Bohmian Mechanics without Pilot Waves," invited contribution, lead article, special issue in honor of Eli Pollak, “Dynamics of Molecular Systems, from Quantum to Classical Dynamics”, B. Poirier, Chem. Phys. 370 (1-3), 4-14 (2010).
• "Quantum Dynamics of Hydrogen Interacting with Single-walled Carbon Nanotubes," J. L. McAfee and B. Poirier, J. Chem. Phys., 130 (6), 064701 (2009) (16 pages), selected for joint publication in:Virtual Journal of Nanoscale Science and Technology,19(8), (2009).