To be rescheduled
Prof Giovanni Ciccotti
Dept of Physics, University of Rome “La Sapienza"
Institute of Application of Calculus (IAC) “Mauro Picone", CNR, Rome School of Physics, University College of Dublin UCD), Dublin
Host: Alin Marin Elena, Computational Chemistry, SCD
Wednesday 13th January 2021 at 14:00-15:00This seminar will take place via Zoom webinar, see joining instructions below.
Statistical Mechanics of polarizable systems (and more) via adiabatic constrainded dynamics of zero-mass particles
Recently a new algorithm, based on holonomic constraints, to solve numerically the dynamics of the shell model for polarization was introduced. The approach, broadly applicable to systems involving adiabatically separated dynamical variables, employs constrained molecular dynamics to strictly enforce the condition that the external force on the fast degrees of freedom, modeled as having zero mass, is null at each time step. The new algorithm is symplectic and fully time reversible, and results in stable and efficient propagation. In this lecture, beyond introducing the new method, I will extend the mechanics of mass-zero constrained dynamics to treat cases where the fast degrees of freedom must satisfy additional conditions. This extension permits to consider first principles molecular dynamics. As for the statistical mechanics of the mass-zero constrained dynamical system I will show that the marginal probability, associated to the real DoF's, properly derives the form intuitively associated to the Born–Oppenheimer probability density. If time remains, I will show the results of test calculations on solid Na via orbital-free density functional dynamics and check the effectiveness of the approach and the favorable scaling of the algorithm with system size.