Dr. William L. Hase (deceased)

Principal Research Interests

• Theory of Unimolecular and Intramolecular Dynamics
• Computer Simulation of Organic and Biochemical Reactions
• Gas-Surface Collisions
• Energy Transfer and Chemical Reactions at Interfaces
• Web-based Computing

Dr. Hase's research group simulates the dynamics of molecular motion and chemical reaction at an atomistic, microscopic level. Classical, semi-classical, and quantum mechanical simulations are performed. The simulation results are used to compare with experiments and to test and develop theoretical models of molecular motion and chemical reactivity. Computer graphics are used to animate and visualize the atomistic simulations. For many chemical problems classical mechanics provides an accurate description of atomic motion and the Hase research group has developed the VENUS computer program for performing classical trajectory simulations. Calculating a classical trajectory or the motion of a semi-classical/quantum wave packet requires the derivatives of the potential energy with respect to the coordinates of each of the atoms. In a direct dynamics simulation these derivatives are obtained directly from a quantum chemistry (QM) electronic structure theory. To perform this type of simulation VENUS is interfaced with quantum chemistry computer programs. For large-scale simulations, a QM/MM calculation may be performed in which part of the potential is represented by both a quantum mechanical theory and the remainder by molecular mechanical (MM) analytic potential energy functions. Dr. Hase also advises computer science graduate students whose research is in the area of scientific computing. Dr. Hase is co-author of the books Chemical Kinetics and Dynamics and Unimolecular Reaction Dynamics. Theory and Experiments.

The current simulations of Dr. Hase's research group include collision- and surface-induced dissociation (CID and SID) of ions (including peptides), the dynamics and role of microsolvation in gas phase S_N2 nucleophilic substitution reactions, intramolecular and unimolecular dynamics, energy transfer and chemical reaction in collisions of projectiles with surfaces, intermolecular energy transfer in the gas and liquid phases, dynamics in supercritical fluids, the aggregation of PAH molecules and the role of cations, interstellar chemistry, post-transition state dynamics, and semi-classical calculation of anharmonic vibrational spectra. The figure shown below is a chemical dynamics simulation of the SID of protonated diglycine. The peptide shatters as it collides with the diamond {111} surface, forming H₂ + NHCH₂ + CONHCH₂COOH⁺.

Representative Publications

• Rethinking the S_N2 Reaction. Xie, J.; Hase, W. L. Science 2016, 352, 32.
• Perspective: Dynamics of Protonated Peptide Ion Collisions with Organic Surfaces. Consonance of Simulation and Experiment. Pratihar, S.; Barnes, G. L.; J. Laskin, J.; and W. L. Hase, W. L. J. Phys. Chem. Lett. 2016, 7, 3142.
• Chemical Dynamics Simulations of Energy Transfer, Surface-Induced Dissociation, Soft-Landing, and Reactive-Landing in Collisions of Protonated Peptide Ions with Organic Surfaces. Pratihar, S.; Barnes, G.; Hase, W. L. Chem. Soc. Rev. 2016, 45, 3595.
• A Zero Point Energy Constraint for Unimolecular Dissociation Reactions. Giving Trajectories Multiple Chances to Dissociate Correctly. Paul, A. K.; Hase, W. L. J. Phys. Chem. A 2016, 120, 372.
• Microsolvated F-(H₂O) + CH₃I S_N2 Reaction Dynamics. An Insight into the Suppressed Formation of Solvated Products. Zhang, J.; Yang, L.; Xie, J.; Hase, W. L. J. Phys. Chem. Lett. 2016, 7, 660.
• Chemical Dynamics Simulations of Intermolecular Energy Transfer: Azulene + N2 Collisions. Kim, H.; Paul, A.; Hase, W. L. J. Phys. Chem. A 2016, 120, 5187.
• Identification of Atomic-Level Mechanisms for Gas-Phase X- + CH3Y SN2 Reactions by Combined Experiments and Simulations. Xie, J.; Otto, R.; Mikosch, J.; Zhang, J.; Wester, R.; Hase, W. L. Acc. Chem. Res. 2014, 47, 2960.
• Properties of Complexes Formed by Na+, Mg2+, and Fe2+ Binding with Benzene Molecules. Kolakkandy, S.; Pratihar, S.; Aquino, A. J. A.; Wang, H.; Hase, W. L. J. Phys. Chem. A 2014, 118, 9500.
• Direct Chemical Dynamics Simulations: Coupling of Classical and Quasiclassical Trajectories with Electronic Structure Theory. Paranjothy, M.; Sun, R.; Zhuang, Y.; Hase, W. L. WIREs Comput. Mol. Sci. 2013, 3, 296.