Department of Materials Science and Engineering, Norwegian University of Science and Technology, NTNU, Trondheim NO-7491, Norway.
SINTEF Energy Research, Trondheim NO-7465, Norway.
J Chem Inf Model. 2021 Feb 22;61(2):840-855. doi: 10.1021/acs.jcim.0c01367. Epub 2021 Feb 10.
We present a new method for computing chemical potential differences of macroscopic systems by sampling fluctuations in small systems. The small system method, presented by Schnell et al. [Schnell et al., J. Phys. Chem. B, 2011, , 10911], is used to create small embedded systems from molecular dynamics simulations, in which fluctuations of the number of particles are sampled. The sampled fluctuations represent the Boltzmann distributed probability of the number of particles. The overlapping region of two such distributions, sampled from two different systems, is used to compute their chemical potential difference. Since the thermodynamics of small systems is known to deviate from the classical thermodynamic description, the particle distributions will deviate from the macroscopic behavior as well. We show how this can be utilized to calculate the size dependence of chemical potential differences and eventually extract the chemical potential difference in the thermodynamic limit. The macroscopic chemical potential difference is determined with a relative error of 3% in systems containing particles that interact through the truncated and shifted Lennard-Jones potential. In addition to computing chemical potential differences in the macroscopic limit directly from molecular dynamics simulation, the new method provides insights into the size dependency that is introduced to intensive properties in small systems.
我们提出了一种新的方法，通过对小系统的波动进行采样来计算宏观系统的化学势差。Schnell 等人提出的小系统方法[Schnell 等人，J. Phys. Chem. B，2011，10911]用于从小分子动力学模拟中创建小嵌入系统，其中对粒子数的波动进行采样。采样波动代表了粒子数的玻尔兹曼分布概率。从两个不同系统中采样的两个这样的分布的重叠区域用于计算它们的化学势差。由于小系统的热力学已知与经典热力学描述存在偏差，因此粒子分布也会偏离宏观行为。我们展示了如何利用这一点来计算化学势差的尺寸依赖性，并最终在热力学极限下提取化学势差。在通过截断和移动 Lennard-Jones 势相互作用的系统中，包含粒子的系统的化学势差可以用相对误差 3%来确定。除了直接从分子动力学模拟中计算宏观极限的化学势差外，新方法还提供了对小系统中引入到强度性质的尺寸依赖性的深入了解。
