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Physical Chemistry Seminar
April 5 @ 4:10 pm - 5:00 pm
Jonathan Prince (Peterson Group)
Modern Electronic Structure Theory: The Search for Chemical Accuracy
Electronic structure theory has progressed significantly within the last few decades, venturing far from the early days of the Hartree-Fock self-consistent field method. Modern electronic structure theory focuses on compound methods, which operate under the idea that we can take a lower level of theory computation (typically, a result from Hartree-Fock, Configuration Interaction, Coupled Cluster or Moller-Plesset perturbation theory) and add in higher level of the theory corrections such as extrapolations to the infinite basis set limit, as well as, relativistic effects. Using the Gaussian-n, Complete Basis Set and Weizmann compound methods, we were able to provide theoretical evidence to justify the claim that the mechanism for the isomerization process of perfluoro-2-azapropene was through either a nitrogen inversion or rotational mechanism. Following the previous study was the realization that what is predicted to be the most accurate compound method (the Weizmann method) doesn’t yield the most accurate result, led us to ask the question “Is there a compound method available that’s both computationally feasible on a workstation computer, as well as, able to produce the best results regardless of the molecule or process being studied?”. What we found was that the Weizmann-2 method is computationally feasible on a workstation computer, as well as, claims to produce chemically accurate results (results within 1 kcal mole-1) from there experimental values for all molecules and processes. However, the Weizmann-2 method has only been tested against thermochemical data with little to no work being done with any kinetic parameter. These realizations sparked are interest to verify the validity of this claim by testing the accuracy of the Weizmann-2 method against a kinetic parameter such as a barrier height. The results of the Weizmann-2 investigation were then used to develop a modification to the Weizmann-2 method which was able to produce chemically accurate barrier heights for all of the well-behaved molecules studied.