Professor John Tully, Yale University. Quantum-Classical Dynamics: Issues and Applications. R.B. Woodward Lectures in the Chemical Sciences, Theoretical Chemistry Seminar.
Conventional Molecular Dynamics (MD) rests on two fundamental assumptions: 1. Nuclear motion evolves by classical mechanics. 2. The forces on the nuclei derive from a single electronic potential energy surface (the Born-Oppenheimer Approximation). There are hosts of chemical processes for which one or both of these assumptions are not adequate. Nuclear motion can exhibit pronounced quantum mechanical effects associated with tunneling, zero-point motion and quantized energy levels. Transitions among multiple electronic states can play a dominant role in processes such as nonradiative transitions, electron transfer, photochemistry, and chemistry at semiconductor and metal surfaces. Mixed quantum-classical dynamics (MQCD) has been an at least partially successful strategy for introducing quantum effects into molecular dynamics simulations, as well as providing a procedure to treat open systems. A crucial concern in MQCD is feedback between the classical and quantum motions. The time-dependent motion of the classical nuclei induces transitions among quantum states. Quantum mechanical transitions, in turn, alter the forces that govern the motion of the classical particles. Proper treatment of this “quantum backreaction” has been a subject of controversy for more than 40 years. Aspects of this issue will be examined, both at a fundamental level and by example. Among the applications presented are the quantum dynamics of proton transfer in solution and inelastic scattering of molecules from metal surfaces. Because metal surfaces exhibit a continuum of infinitesimally spaced conduction electron levels, the latter is an extreme example of anticipated inadequacy of the Born-Oppenheimer Approximation.
LOCATION:MIT, Room 4-163 STATUS:CONFIRMED DTSTART:20131211T210000Z DTEND:20131211T230000Z END:VEVENT END:VCALENDAR