dc.contributor.author Welsch, R en dc.contributor.author Song, K en dc.contributor.author Shi, Q en dc.contributor.author Althorpe, Stuart en dc.contributor.author Miller, TF en dc.date.accessioned 2017-02-02T14:03:43Z dc.date.available 2017-02-02T14:03:43Z dc.date.issued 2016-11-28 en dc.identifier.issn 0021-9606 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/262237 dc.description.abstract We investigate the calculation of approximate non-equilibrium quantum time correlation functions (TCFs) using two popular path-integral-based molecular dynamics methods, ring-polymer molecular dynamics (RPMD) and centroid molecular dynamics (CMD). It is shown that for the cases of a sudden vertical excitation and an initial momentum impulse, both RPMD and CMD yield non-equilibrium TCFs for linear operators that are exact for high temperatures, in the $\textit{t}$ = 0 limit, and for harmonic potentials; the subset of these conditions that are preserved for non-equilibrium TCFs of non-linear operators is also discussed. Furthermore, it is shown that for these non-equilibrium initial conditions, both methods retain the connection to Matsubara dynamics that has previously been established for equilibrium initial conditions. Comparison of non-equilibrium TCFs from RPMD and CMD to Matsubara dynamics at short times reveals the orders in time to which the methods agree. Specifically, for the position-autocorrelation function associated with sudden vertical excitation, RPMD and CMD agree with Matsubara dynamics up to O($\textit{t}$$^{4}) and O(\textit{t}$$^{1}$), respectively; for the position-autocorrelation function associated with an initial momentum impulse, RPMD and CMD agree with Matsubara dynamics up to O($\textit{t}$$^{5}) and O(\textit{t}$$^{2}$), respectively. Numerical tests using model potentials for a wide range of non-equilibrium initial conditions show that RPMD and CMD yield non-equilibrium TCFs with an accuracy that is comparable to that for equilibrium TCFs. RPMD is also used to investigate excited-state proton transfer in a system-bath model, and it is compared to numerically exact calculations performed using a recently developed version of the Liouville space hierarchical equation of motion approach; again, similar accuracy is observed for non-equilibrium and equilibrium initial conditions. dc.description.sponsorship R.W. acknowledges financial support from the Deutsche Forschungsgemeinschaft under Grant No. We 5762/1-1. S.C.A. acknowledges support from the Leverhulme Trust, the Chinese Academy of Sciences visiting professorship for senior international scientists (Grant No. 2013T2J0022) program, and the hospitality of the Miller group at Caltech. Q.S. acknowledges support from the National Natural Science Foundation of China (Grant No. 21290194). T.F.M. acknowledges support from the National Science Foundation (NSF) CAREER Award under Grant No. CHE-1057112 and from the Office of Naval Research (ONR) under Grant No. N00014-16-1-2761. dc.language eng en dc.language.iso en en dc.publisher American Institute of Physics dc.title Non-equilibrium dynamics from RPMD and CMD en dc.type Article prism.issueIdentifier 20 en prism.number 204118 en prism.publicationDate 2016 en prism.publicationName Journal of Chemical Physics en prism.volume 145 en dc.identifier.doi 10.17863/CAM.7492 dcterms.dateAccepted 2016-11-07 en rioxxterms.versionofrecord 10.1063/1.4967958 en rioxxterms.version VoR en rioxxterms.licenseref.uri http://www.rioxx.net/licenses/all-rights-reserved en rioxxterms.licenseref.startdate 2016-11-28 en dc.contributor.orcid Althorpe, Stuart [0000-0003-1288-8070] dc.identifier.eissn 1089-7690 rioxxterms.type Journal Article/Review en pubs.funder-project-id Leverhulme Trust (RF-2014-091) cam.issuedOnline 2016-11-30 en rioxxterms.freetoread.startdate 2017-11-28
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