The time-dependent variational principle, or Dirac-Frenkel variational principle, provides a systematic strategy for defining the optimal time evolution of approximate wavefunctions. For complex analytic parametrizations, the variational equations of motion exhibit a symplectic structure, associated with a generalized Hamiltonian flow. Here, we focus on multiconfigurational wavefunctions built from Gaussian wavepackets (GWPs), within the Gaussian-based multiconfiguration time-dependent Hartree (G-MCTDH) approach and its variational multiconfigurational Gaussian (vMCG) variant. These methods have proven versatile tools for on-the-fly calculations as well as the explicit representation of system-bath problems. More recently, we extended these methods such as to remedy the lack of flexibility of the Frozen Gaussian (FG), or coherent state, basis sets that are most often employed. To this end, hierarchical two-layer and multi-layer schemes were introduced, similarly to the multi-layer multiconfiguration time-dependent Hartree (ML-MCTDH) method. We report on the first implementation of the two-layer (2L-)GMCTDH method in an in-house code, along with applications to vibrational energy transport, high-dimensional nonadiabatic dynamics, and the computation of vibronic spectra for strongly anharmonic systems. We further report on a classical-limit formulation yielding a multi-configuration Ehrenfest (MCE) dynamics, and on recent developments based on variational equations of motions within a density matrix setting. Against this background, a perspective is given on the application of these methods to carry out quantum dynamics in condensed-phase environments.

Multiconfigurational Gaussian wavepacket dynamics: Interpolating between accurate quantum dynamics and the quantum-classical limit

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.