A method to calculate the probability distribution for systems with large energy barriers
A method to calculate the probability distribution for systems with large energy barriers
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DOI：
10.1016/s0301-0104(96)00247-9
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发表时间：
1996-12-15
期刊：
影响因子：
2.3
通讯作者：
Karlstrom, G
中科院分区：
文献类型：
--
作者：
Engkvist, O;Karlstrom, G
提出了一种计算分子系统中自由能差异的新方法。基本思想涉及使用改进的蒙特卡罗程序自动生成伞采样势。这种势能具有使分子的所有构象在收敛时具有同等可能性的特性。因此最终的伞势将等于平均力势的负值，将给出两个例子。在第一个示例中，使用新方法和标准 Metropolis 算法在气相中进行了 1,2-二甲氧基乙烷的模拟。在第二种方法中，我们应用了所提出的方案来研究由硬球介导的两个硬墙之间的有效相互作用。新开发的技术已与标准 Metropolis 算法以及施加在墙壁上的力的直接积分进行了比较。三种技术之间的比较表明，只要所研究的障碍远高于 kT，新方法比标准技术更快地收敛到正确的平均力势。
A new way to calculate free energy differences in a molecular system is presented. The fundamental idea involves using a modified Monte Carlo procedure to automatically generate an umbrella sampling potential. This potential will have the property of making all conformations of the molecule equally probable at convergence. Thus the final umbrella potential will be equal to the negative value of the potential of mean force, Two examples will be given. In the first example, simulations of 1,2-dimethoxyethane have been performed in gas phase with the new method and with the standard Metropolis algorithm. In the second approach we have applied the proposed scheme to study the effective interaction between two hard walls mediated by hard spheres. The newly developed technique has been compared with a standard Metropolis algorithm and with a direct integration of the force exerted on the walls. Comparison between the three techniques reveals that the new method converges much faster to a correct potential of mean force than standard techniques, provided that the studied barriers are much higher than kT.