Two different approaches for investigating the quantum dynamics of multiple modes for reactions in complex systems are presented. The first is time-dependent self-consistent-field dynamics based on a reaction path Hamiltonian (TDSCF-RPH), which allows the calculation of the real-time quantum dynamics of gas-phase chemical reactions involving polyatomic molecules. The TDSCF-RPH equations of motion are derived for straightline diabatic reaction path Hamiltonians, including the case in which the minimum-energy path has negligible curvature and the case in which the minimum-energy path has large curvature but the system follows a straightline path instead of the minimum-energy path. The advantage of the diabatic representation is that the TDSCF dynamics reduces to a one-dimensional numerical time propagation, even for the case of large coupling between the vibrational modes. The second approach is the multiconfigurational molecular dynamics with quantum transitions (MC-MDQT) method, which combines a multiconfigurational self-consistent-field (MC-SCF) formulation for the vibrational wavefunction with the MDQT non-adiabatic mixed quantum-classical molecular dynamics method. The MC-MDQT method allows the quantum dynamical treatment of multiple modes within a mixed quantum-classical framework for reactions in condensed-phase systems. The advantages of the MC-MDQT method are that it incorporates the significant correlation between the quantum modes, is valid in the adiabatic and non-adiabatic limits and the intermediate regime, and provides real-time dynamical information. The application of MC-MDQT to simulate the real-time non-equilibrium quantum dynamics of proton transport along protonated chains of water molecules is presented.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry