An efficient quantum mechanical method for radical pair recombination reactions

作者：Lewis Alan M^*; Fay Thomas P; Manolopoulos David E

来源：Journal of Chemical Physics, 2016, 145(24): 244101.

DOI：10.1063/1.4972277

The standard quantum mechanical expressions for the singlet and triplet survival probabilities and product yields of a radical pair recombination reaction involve a trace over the states in a combined electronic and nuclear spin Hilbert space. If this trace is evaluated deterministically, by performing a separate time-dependent wavepacket calculation for each initial state in the Hilbert space, the computational effort scales as O (Z(2) log Z), where Z is the total number of nuclear spin states. Here we show that the trace can also be evaluated stochastically, by exploiting the properties of spin coherent states. This results in a computational effort of O (MZ log Z), where M is the number of Monte Carlo samples needed for convergence. Example calculations on a strongly coupled radical pair with Z > 10(6) show that the singlet yield can be converged to graphical accuracy using just M = 200 samples, resulting in a speed up by a factor of > 5000 over a standard deterministic calculation. We expect that this factor will greatly facilitate future quantum mechanical simulations of a wide variety of radical pairs of interest in chemistry and biology. Published by AIP Publishing.

• 出版日期2016-12-28