Berlin 2015 – scientific programme

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SYME: Symposium Frontiers of Electronic Structure Theory: Many-body Effects on the Nano-Scale

SYME 2: Frontiers of Electronic Structure Theory: Many-Body Effects on the Nano-Scale I

SYME 2.5: Talk

Tuesday, March 17, 2015, 11:45–12:00, MA 004

Can we get reliable quantum dynamics simulations for vibrational spectra in the condensed phase? — •Mariana Rossi¹, David Manolopoulos¹, and Michele Ceriotti² — ¹University of Oxford, Oxford, UK — ²EPFL, Lausanne, Switzerland

At the level of accuracy we can now achieve in first-principles calculations, the inclusion of more subtle nuclear quantum effects (NQE) in simulations become more relevant. However, their inclusion is challenging for anharmonic and dynamical processes, in particular in the condensed phase. We show a new method to approximate quantum corrections in time-dependent properties based on a path integral framework, called thermostatted ring polymer molecular dynamics (TRPMD) [1], which is immune to pathological problems of previously proposed methods. We perform a systematic comparison of TRPMD with other approaches that rely on different approximations to quantum dynamics, to assess their performance for the IR spectrum of HOD in D₂O and water at different phases/temperatures [2]. Using an empirical potential energy surface (q-TIP4P/f), we find that the different techniques are largely consistent with one another, within a few tens of cm⁻¹. Comparison with classical molecular dynamics demonstrates the importance of NQE even up to 600K. The cross validation between these different approaches provides clues to limitations of their underlying approximations and paves the way for more reliable approaches to nuclear quantum dynamics that are feasible together with electronic structure methods. [1] M. Rossi, M. Ceriotti, D. Manolopoulos, JCP 140, 234116 (2014); [2] M. Rossi, et al., JCP 141, 181101 (2014)