The Development of Rigorously Correct, Dynamical Pseudopotentials for Use in Mixed Quantum Classical Simulations in the Condensed Phase

Seminar series
Physical Chemistry Seminar
Thu, May 29 12:00pm
2033 Young Hall
Speaker Argyris Kahros
University of California, Los Angeles
Dept. of Chemistry and Biochemistry

Abstract: Ideally, to study a quantum mechanical process, one would solve the Schrödinger equation for all the electrons in a system.  This calculation, however, becomes prohibitive as the system size becomes large and more than a few electrons become involved.  One way to circumvent this dilemma is to employ a mixed quantum classical approach (MQC).  This involves treating the majority of the system classically, with Newtonian mechanics, and only a few electrons quantum mechanically, employing pseudopotentials to couple these degrees of freedom and implicitly include the effects of all the electrons in the system.  These potentials can be empirical or analytic in nature, but to date, virtually all have been subject to the frozen core approximation (FCA), which neglects how changes in the implicitly treated electrons affect the generated pseudopotential.  In this talk, the development of novel methods for the generation of rigorously correct pseudopotentials that go beyond the FCA will be presented.  The new formalism is then applied first to the sodium dimer cation molecule, and then to investigate the nature of the hydrated electron, a system that has been the subject of controversy over the past several years.  In both cases, it will be shown that rigorously correct pseudopotentials that go beyond the FCA are essential in the quest to accurately predict experimental observables.  In the case of the hydrated electron, the resulting dynamics from employing such potentials will be explored with special attention given to the sensitivity of the dynamics to the details of the calculated pseudopotential.