Maximilian Saller


Last Name

Saller

First Name

Maximilian

ORCID

0000-0003-3845-6831

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20203
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Publications 1 - 3 of 3
  • Benchmarking Quasiclassical Mapping Hamiltonian Methods for Simulating Electronically Nonadiabatic Molecular Dynamics
    Item type: Journal Article
    Gao, Xing; Saller, Maximilian; Liu, Yudan; et al. (2020)
    Journal of Chemical Theory and Computation
    Quasi-classical mapping Hamiltonian methods have recently emerged as a promising approach for simulating electronically nonadiabatic molecular dynamics. The classical-like dynamics of the overall system within these methods makes them computationally feasible, and they can be derived based on well-defined semiclassical approximations. However, the existence of a variety of different quasi-classical mapping Hamiltonian methods necessitates a systematic comparison of their respective advantages and limitations. Such a benchmark comparison is presented in this paper. The approaches compared include the Ehrenfest method, the symmetrical quasi-classical (SQC) method, and five variations of the linearized semiclassical (LSC) method, three of which employ a modified identity operator. The comparison is based on a number of popular nonadiabatic model systems; the spin-boson model, a Frenkel biexciton model, and Tully’s scattering models 1 and 2. The relative accuracy of the different methods is tested by comparing with quantum-mechanically exact results for the dynamics of the electronic populations and coherences. We find that LSC with the modified identity operator typically performs better than the Ehrenfest and standard LSC approaches. In comparison to SQC, these modified methods appear to be slightly more accurate for condensed phase problems, but for scattering models there is little distinction between them.
  • Path‐Integral Approaches to Non‐Adiabatic Dynamics
    Item type: Book Chapter
    Saller, Maximilian; Runeson, Johan E.; Richardson, Jeremy (2020)
    Quantum Chemistry and Dynamics of Excited States: Methods and Applications
    In this chapter, we describe methods for simulating non‐adiabatic dynamics based on the path‐integral formulation of quantum mechanics. In order to employ trajectory calculations to a system of more than one electronic state, we introduce the mapping formalism and explain how this approach can be used with linearized semiclassical or ring‐polymer molecular dynamics.
  • Improved population operators for multi-state nonadiabatic dynamics with the mixed quantum-classical mapping approach
    Item type: Journal Article
    Saller, Maximilian; Kelly, Aaron; Richardson, Jeremy (2020)
    Faraday Discussions
    The mapping approach addresses the mismatch between the continuous nuclear phase space and discrete electronic states by creating an extended, fully continuous phase space using a set of harmonic oscillators to encode the populations and coherences of the electronic states. Existing quasiclassical dynamics methods based on mapping, such as the linearised semiclassical initial value representation (LSC-IVR) and Poisson bracket mapping equation (PBME) approaches, have been shown to fail in predicting the correct relaxation of electronic-state populations following an initial excitation. Here we generalise our recently published modification to the standard quasiclassical approximation for simulating quantum correlation functions. We show that the electronic-state population operator in any system can be exactly rewritten as a sum of a traceless operator and the identity operator. We show that by treating the latter at a quantum level instead of using the mapping approach, the accuracy of traditional quasiclassical dynamics methods can be drastically improved, without changes to their underlying equations of motion. We demonstrate this approach for the seven-state Frenkel-exciton model of the Fenna–Matthews–Olson light harvesting complex, showing that our modification significantly improves the accuracy of traditional mapping approaches when compared to numerically exact quantum results.
Publications 1 - 3 of 3