Quantum dynamics using pseudo-particle trajectories: A new approach based on the multiconfiguration time-dependent Hartree method

Quantum molecular-dynamics simulations are an important way of gaining info rmation on the molecular level about chemical systems. In this paper, a new method for the approximate solution of the time-dependent Schrodinger equa tion is presented. This is a reformulation of the multiconfiguration time-d ependent Hartree (MCTDH) wave packet propagation method, which is transform ed so that the evolution of the wave function can be represented by pseudo- particle trajectories. In this way, the poor scaling of computational resou rces with system size attending all exact solutions of the time-dependent S chrodinger equation are circumvented. The equations of motion for the traje ctories and the wave function expansion coefficients (importance of each tr ajectory for the representation) are derived using a variational principle. Other than the MCTDH ansatz, no major approximations have been introduced, and the method converges on the numerically exact solution. Importantly, t he trajectories are not classical trajectories, and are coupled by nonlocal effects. A strategy for the practical solution of the equations of motion is then detailed. (C) 2001 American Institute of Physics.