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All Publications

  • Ring-polymer, centroid, and mean-field approximations to multi-time Matsubara dynamics JOURNAL OF CHEMICAL PHYSICS Jung, K. A., Videla, P. E., Batista, V. S. 2020; 153 (12): 124112


    Based on a recently developed generalization of Matsubara dynamics to the multi-time realm, we present a formal derivation of multi-time generalizations of ring-polymer molecular dynamics, thermostatted ring-polymer molecular dynamics (TRPMD), centroid molecular dynamics (CMD), and mean-field Matsubara dynamics. Additionally, we analyze the short-time accuracy of each methodology. We find that for multi-time correlation functions of linear operators, (T)RPMD is accurate up to order t3, while CMD is only correct up to t, indicating a degradation in the accuracy of these methodologies with respect to the single-time counterparts. The present work provides a firm justification for the use of path-integral-based approximations for the calculation of multi-time correlation functions.

    View details for DOI 10.1063/5.0021843

    View details for Web of Science ID 000577137700002

    View details for PubMedID 33003707

  • Energy transfer under natural incoherent light: Effects of asymmetry on efficiency JOURNAL OF CHEMICAL PHYSICS Jung, K. A., Brumer, P. 2020; 153 (11): 114102


    The non-equilibrium stationary coherences that form in donor-acceptor systems are investigated to determine their relationship to the efficiency of energy transfer to a neighboring reaction center. It is found that the effects of asymmetry in the dimer are generally detrimental to the transfer of energy. Four types of systems are examined, arising from combinations of localized trapping, delocalized (Forster) trapping, eigenstate dephasing, and site basis dephasing. In the cases of site basis dephasing, the interplay between the energy gap of the excited dimer states and the environment is shown to give rise to a turnover effect in the efficiency under weak dimer coupling conditions. Furthermore, the nature of the coherences and associated flux is interpreted in terms of pathway interference effects. In addition, regardless of the cases considered, the ratio of the real part and the imaginary part of the coherences in the energy-eigenbasis tends to a constant value in the steady state limit.

    View details for DOI 10.1063/5.0020576

    View details for Web of Science ID 000573433800002

    View details for PubMedID 32962363

  • Two-dimensional Raman spectroscopy of Lennard-Jones liquids via ring-polymer molecular dynamics JOURNAL OF CHEMICAL PHYSICS Tong, Z., Videla, P. E., Jung, K. A., Batista, V. S., Sun, X. 2020; 153 (3): 034117


    The simulation of multidimensional vibrational spectroscopy of condensed-phase systems including nuclear quantum effects is challenging since full quantum-mechanical calculations are still intractable for large systems comprising many degrees of freedom. Here, we apply the recently developed double Kubo transform (DKT) methodology in combination with ring-polymer molecular dynamics (RPMD) for evaluating multi-time correlation functions [K. A. Jung et al., J. Chem. Phys. 148, 244105 (2018)], providing a practical method for incorporating nuclear quantum effects in nonlinear spectroscopy of condensed-phase systems. We showcase the DKT approach in the simulation of the fifth-order two-dimensional (2D) Raman spectroscopy of Lennard-Jones liquids as a prototypical example, which involves nontrivial nonlinear spectroscopic observables of systems described by anharmonic potentials. Our results show that the DKT can faithfully reproduce the 2D Raman response of liquid xenon at high temperatures, where the system behaves classically. In contrast, liquid neon at low temperatures exhibits moderate but discernible nuclear quantum effects in the 2D Raman response compared to the responses obtained with classical molecular dynamics approaches. Thus, the DKT formalism in combination with RPMD simulations enables simulations of multidimensional optical spectroscopy of condensed-phase systems that partially account for nuclear quantum effects.

    View details for DOI 10.1063/5.0015436

    View details for Web of Science ID 000553907500006

    View details for PubMedID 32716164

  • Multi-time formulation of Matsubara dynamics JOURNAL OF CHEMICAL PHYSICS Jung, K. A., Videla, P. E., Batista, V. S. 2019; 151 (3): 034108


    Matsubara dynamics has recently emerged as the most general form of a quantum-Boltzmann-conserving classical dynamics theory for the calculation of single-time correlation functions. Here, we present a generalization of Matsubara dynamics for the evaluation of multitime correlation functions. We first show that the Matsubara approximation can also be used to approximate the two-time symmetrized double Kubo transformed correlation function. By a straightforward extension of these ideas to the multitime realm, a multitime Matsubara dynamics approximation can be obtained for the multitime fully symmetrized Kubo transformed correlation function. Although not a practical method, due to the presence of a phase-term, this multitime formulation of Matsubara dynamics represents a benchmark theory for future development of Boltzmann preserving semiclassical approximations to general higher order multitime correlation functions. It also reveals a connection between imaginary time-ordering in the path integral and the classical dynamics of multitime correlation functions.

    View details for DOI 10.1063/1.5110427

    View details for Web of Science ID 000476588700034

    View details for PubMedID 31325942

  • Inclusion of nuclear quantum effects for simulations of nonlinear spectroscopy JOURNAL OF CHEMICAL PHYSICS Jung, K. A., Videl, P. E., Batista, V. S. 2018; 148 (24): 244105


    The computation and interpretation of nonlinear vibrational spectroscopy is of vital importance for understanding a wide range of dynamical processes in molecular systems. Here, we introduce an approach to evaluate multi-time response functions in terms of multi-time double symmetrized Kubo transformed thermal correlation functions. Furthermore, we introduce a multi-time extension of ring polymer molecular dynamics to evaluate these Kubo transforms. Benchmark calculations show that the approximations are useful for short times even for nonlinear operators, providing a consistent improvement over classical simulations of multi-time correlation functions. The introduced methodology thus provides a practical way of including nuclear quantum effects in multi-time response functions of non-linear optical spectroscopy.

    View details for DOI 10.1063/1.5036768

    View details for Web of Science ID 000437190300053

    View details for PubMedID 29960352

  • Electron Transfer Assisted by Vibronic Coupling from Multiple Modes JOURNAL OF CHEMICAL THEORY AND COMPUTATION Chaudhuri, S., Hedstrom, S., Mendez-Hernandez, D. D., Hendrickson, H. P., Jung, K. A., Ho, J., Batista, V. S. 2017; 13 (12): 6000–6009


    Understanding the effect of vibronic coupling on electron transfer (ET) rates is a challenge common to a wide range of applications, from electrochemical synthesis and catalysis to biochemical reactions and solar energy conversion. The Marcus-Jortner-Levich (MJL) theory offers a model of ET rates based on a simple analytic expression with a few adjustable parameters. However, the MJL equation in conjunction with density functional theory (DFT) has yet to be established as a predictive first-principles methodology. A framework is presented for calculating transfer rates modulated by molecular vibrations, that circumvents the steep computational cost which has previously necessitated approximations such as condensing the vibrational manifold into a single empirical frequency. Our DFT-MJL approach provides robust and accurate predictions of ET rates spanning over 4 orders of magnitude in the 106-1010 s-1 range. We evaluate the full MJL equation with a Monte Carlo sampling of the entire active space of thermally accessible vibrational modes, while using no empirical parameters. The contribution to the rate of individual modes is illustrated, providing insight into the interplay between vibrational degrees of freedom and changes in electronic state. The reported findings are valuable for understanding ET rates modulated by multiple vibrational modes, relevant to a broad range of systems within the chemical sciences.

    View details for DOI 10.1021/acs.jctc.7b00513

    View details for Web of Science ID 000418205100016

    View details for PubMedID 29095611