Efficient transition path sampling for systems with multiple reaction pathways.
A new algorithm is developed for sampling transition paths and computing reaction rates. To illustrate the use of this method, we study a two-dimensional system that has two reaction pathways: one pathway is straight with a relatively high barrier and the other is roundabout with a lower barrier. The transition rate and the ratio between the numbers of the straight and roundabout transition paths are computed for a wide range of temperatures. Our study shows that the harmonic approximation for fluctuations about the steepest-descent paths is not valid even at relatively low temperatures and, furthermore, that factors related to entropy have to be determined by the global geometry of the potential-energy surface (rather than just the local curvatures alone) for complex reaction systems. It is reasonable to expect that this algorithm is also applicable to higher dimensional systems.
Chen
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Department of Physics, University of Texas at San Antonio, San Antonio, Texas 78249-0697, USA. liao.chen@utsa.edu
Nash
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Horing
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D000465:Algorithms; D002627:Chemistry, Physical / Q000379:methods*; D003198:Computer Simulation; D004058:Diffusion; D019277:Entropy; D008956:Models, Chemical; D015233:Models, Statistical; D008962:Models, Theoretical; D016011:Normal Distribution; D013696:Temperature; D013816:Thermodynamics