Center of Smart Interfaces, Technische Universität Darmstadt, Petersenstrasse 17, 64287 Darmstadt, Germany.
J Chem Phys. 2012 Oct 21;137(15):154113. doi: 10.1063/1.4758936.
The representability and transferability of effective pair potentials used in multiscale simulations of soft matter systems is ill understood. In this paper, we study liquid state systems composed of n-alkanes, the coarse-grained (CG) potential of which may be assumed pairwise additive and has been obtained using the conditional reversible work (CRW) method. The CRW method is a free-energy-based coarse-graining procedure, which, by means of performing the coarse graining at pair level, rigorously provides a pair potential that describes the interaction free energy between two mapped atom groups (beads) embedded in their respective chemical environments. The pairwise nature of the interactions combined with their dependence on the chemically bonded environment makes CRW potentials ideally suited in studies of chemical transferability. We report CRW potentials for hexane using a mapping scheme that merges two heavy atoms in one CG bead. It is shown that the model is chemically and thermodynamically transferable to alkanes of different chain lengths in the liquid phase at temperatures between the melting and the boiling point under atmospheric (1 atm) pressure conditions. It is further shown that CRW-CG potentials may be readily obtained from a single simulation of the liquid state using the free energy perturbation method, thereby providing a fast and versatile molecular coarse graining method for aliphatic molecules.
有效对力在软物质多尺度模拟中的表示和传递性理解得还不够透彻。在本文中，我们研究了由 n-烷烃组成的液态系统，其粗粒化（CG）势可以假定为两两相加，并使用条件可逆功（CRW）方法获得。CRW 方法是一种基于自由能的粗粒化方法，通过在对级进行粗粒化，严格地提供了一个对力，描述了嵌入其各自化学环境中的两个映射原子组（珠子）之间的相互作用自由能。相互作用的两两性质及其对化学键合环境的依赖性使 CRW 对力非常适合于化学可转移性的研究。我们报告了使用将两个重原子合并到一个 CG 珠子中的映射方案的正己烷的 CRW 对力。结果表明，该模型在大气（1 atm）压力条件下，在熔点和沸点之间的温度范围内，对于液态中不同链长的烷烃在化学上和热力学上都是可转移的。进一步表明，CRW-CG 对力可以从液体状态的单次模拟中使用自由能微扰法很容易地获得，从而为脂肪族分子提供了一种快速而通用的分子粗粒化方法。
