Regensburg 2013 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 43: Computational Materials Modelling - Transport, Excitations, Time Dependence II
MM 43.5: Talk
Wednesday, March 13, 2013, 17:30–17:45, H24
Nuclear quantum effects in ab initio IR spectra of water clusters and peptides — •Mariana Rossi1, Volker Blum1, Carsten Baldauf1, Michele Ceriotti2, and Matthias Scheffler1 — 1Fritz-Haber-Institut, Berlin, Germany — 2University of Oxford, UK
Nuclear quantum effects (NQE) are important in biochemical-related processes (e.g., Ref. [1]), but still present a challenge for ab initio (AI) treatments, especially regarding dynamical quantities. We have recently implemented two features in the all-electron code FHI-aims [2], that allow for an efficient and accurate estimation of NQE from an AI perspective: (i) Generalized Langevin Equation based thermostats (GLE) [3] that can approximate NQE, and (ii) an interface to a wrapper code [4] that performs path integral (PI) ring-polymer molecular dynamics (RPMD) and centroid molecular dynamics (CMD). With these methodologies, we quantify NQE effects in IR spectra of protonated water clusters and protonated peptides. IR spectra obtained from classical AI microcanical simulations started from GLE-thermostated runs successfully approximate NQE for small protonated water clusters. However, we provide a simple physical reason why for large and floppy peptides this approximation can fail even qualitatively, making necessary the explicit inclusion of NQE. Using AI PI based methods we can also reproduce key features of the IR spectra of Zundel-like cations observed experimentally. [1] Masgrau et al., Science 312, 237 (2006) [2] Blum et al., CPC 180, 2175 (2009); [3] Ceriotti, Bussi, Parrinello, JCTC 6, 1170 (2010); [4] Ceriotti, More, Manolopoulos, private communication.