Comparison of full multiple spawning, trajectory surface hopping, and converged quantum mechanics for electronically nonadiabatic dynamics

Abstract

Time-dependent quantum wave packet dynamics of the C + OH reaction on the excited electronic state J. Chem. Phys. 138, 094318 (2013); 10.1063/1.4793395 Dynamics of the O ( P 3 ) + H 2 reaction at low temperatures: Comparison of quasiclassical trajectory with quantum scattering calculations Quantum reactive scattering in three dimensions using adiabatically adjusting principal axis hyperspherical coordinates: Periodic distributed approximating functional method for surface functionsWe present calculations employing the simplest version of the full multiple spawning method, FMS-M or minimal FMS, for electronically nonadiabatic quantum dynamics using three model potential energy matrices with different strengths and ranges for the diabatic coupling. We first demonstrate stability of the branching probabilities and final energy distributions with respect to the parameters in the FMS-M method. We then compare the method to a variety of other semiclassical methods, as well as to accurate quantum mechanical results for three-dimensional atom-diatom reactions and quenching processes; the deviations of the semiclassical results from the accurate quantum mechanical ones are averaged over nine cases. In the adiabatic electronic representation, the FMS-M method provides some improvement over Tully's fewest switches trajectory surface hopping method. However, both methods, irrespective of electronic representation, systematically overpredict the extent of reaction in comparison to the exact quantum mechanical results. The present work provides a baseline for understanding the simplest member of the hierarchy of FMS methods and its relationship to established surface hopping methods.

The second-order Ehrenfest method

“…It is important to keep in mind that it succeeds in describing nuclear motion if the potential energy surfaces of the various electronic states are similar in topology and energies [20]. However, in the case of weakly coupled electronic states, the nuclear motion will be dominated by the potential corresponding to the highly populated electronic state and regions of space accessible only on the sparsely populated electronic state may not be explored properly [28,29]. One advantage of the Ehrenfest method is that its applications and results do not depend on the choice of basis functions (if complete) and can, in principle, be applied without choosing basis functions by numerical integration of equation (9).…”

Between ethylene and polyenes - the non-adiabatic dynamics of cis-dienes

“…The initial 40 (24 for Me 4 -CPD) TBFs were placed on S 1 and propagated for 193.5 fs (8000 au) with a time step of 0.39 fs (16 au) using the independent first-generation approximation. 69,73 The final time was chosen long enough to capture the essential dynamics on the excited states. 59 In cases where all population (>99%) had been transferred to the ground state before the final time was reached, the calculation was stopped as our focus here is on the excited state dynamics and timescale of non-adiabatic transfer and not on possible thermal reactions taking place on the vibrationally hot ground electronic state.…”

Efficient real-space configuration-interaction method for the simulation of multielectron mixed quantum and classical nonadiabatic molecular dynamics in the condensed phase

“…This is because nonadiabatic dynamics requires the full many-electron wave function for both the ground and excited states. Thus, condensed phase systems studied with nonadiabatic dynamics, such as solvated electrons, [8][9][10][11] proton transfer, 12,13 charge-transfer-tosolvent ͑CTTS͒, 14 -16 and donor-acceptor electron transfer complexes, 17 typically are simulated with only a single quan-tum degree of freedom. 18 This restriction to a single quantum degree of freedom is unfortunate because there are several hints that one-electron treatments do not always properly describe the electronic structure of solvated systems.…”