Nonequilibrium umbrella sampling in spaces of many order parameters
Nonequilibrium umbrella sampling in spaces of many order parameters
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DOI：
10.1063/1.3070677
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发表时间：
2009-02-21
影响因子：
4.4
通讯作者：
Dinner, Aaron R.
中科院分区：
文献类型：
--
作者：
Dickson, Alex;Warmflash, Aryeh;Dinner, Aaron R.
我们最近引入了一种伞形抽样方法，用于获得投影到任意数量的坐标上的非平衡稳态概率分布(序参数)[A.WarmFlash，P.Bhimalapuram，和A.R.Dner，J.Chem。太棒了。127、154112(2007年)]。在这里，我们展示了我们的算法如何与可逆过程的有限温度弦方法的图像更新过程相结合[E.Vanden-Eijnden和M.Venturoli，《重温有限温度弦方法计算反应管和自由能》，J.太棒了。能够对序参数的多维空间中的路径附近的非平衡稳态进行受限采样。对于稳态之间的转变的研究，改进的算法导致了随序参数的数量而改进的缩放，以及逐步细化强制采样区域的能力。我们将该算法应用于驱动布朗运动的二维模型和剪切作用下的粗粒(Ising)形核模型。结果表明，序参数的选择对模拟的收敛有很大影响；为了确保无功磁通主要包含在序参数空间中的管内，需要使用不同于以往用于Ising系统中采样过渡路径的局部磁化变量。讨论了该方法与其他采样路径集成统计的算法之间的关系。
We recently introduced an umbrella sampling method for obtaining nonequilibrium steady-state probability distributions projected onto an arbitrary number of coordinates that characterize a system (order parameters) [A. Warmflash, P. Bhimalapuram, and A. R. Dinner, J. Chem. Phys. 127, 154112 (2007)]. Here, we show how our algorithm can be combined with the image update procedure from the finite-temperature string method for reversible processes [E. Vanden-Eijnden and M. Venturoli, "Revisiting the finite temperature string method for calculation of reaction tubes and free energies," J. Chem. Phys. (in press)] to enable restricted sampling of a nonequilibrium steady state in the vicinity of a path in a many-dimensional space of order parameters. For the study of transitions between stable states, the adapted algorithm results in improved scaling with the number of order parameters and the ability to progressively refine the regions of enforced sampling. We demonstrate the algorithm by applying it to a two-dimensional model of driven Brownian motion and a coarse-grained (Ising) model for nucleation under shear. It is found that the choice of order parameters can significantly affect the convergence of the simulation; local magnetization variables other than those used previously for sampling transition paths in Ising systems are needed to ensure that the reactive flux is primarily contained within a tube in the space of order parameters. The relation of this method to other algorithms that sample the statistics of path ensembles is discussed.