2016/03/23 by Igal Aharonovich, Aharonovich, Igal, Avi Pe'er +1
Physics and Astronomy · #Chemical Physics (physics.chem-ph) #Computational Physics (physics.comp-ph) #FOS: Physical sciences #physics.chem-ph #physics.comp-ph
paper · pdf · doi:10.48550/arxiv.1603.07242
arxiv created 2016/03/23 · arxiv updated 2016/03/24
We present a simple method to expedite simulation of quantum wave-packet dynamics by more than a factor of 2 with the Strang split-operator propagation. Dynamics of quantum wave-packets are often evaluated using the the Strang split-step propagation, where the kinetic part of the Hamiltonian T and the potential part V are piecewise integrated according to e^- i H δt ≈ e^- i V δt/2 e^- i Tδt e^- i V δt/2, which is accurate to second order in the propagation time δt. In molecular quantum dynamics, the potential propagation occurs over multiple coupled potential surfaces and requires matrix exponentiation for each position in space and time which is computationally demanding. Our method employs further splitting of the potential matrix V into a diagonal space dependent part VD(R) and an off-diagonal time-dependent coupling-field VOD(t), which then requires only a single matrix exponentiation for each time-step, considerably reducing the calculation time even in the simplest two-surface interaction (∼70% reduction observed in potential propagation time). We analyze the additional error due to the potential splitting and show it to be small compared to the inherent error associated with the kinetic/potential splitting.