Department of Chemistry, College of Staten Island, City University of New York, 2800 Victory Boulevard, Staten Island, New York 10314, USA.
J Chem Phys. 2010 Jan 28;132(4):044906. doi: 10.1063/1.3290955.
A Monte Carlo algorithm is developed to compute the autocorrelation function of liquids and the corresponding spatial correlation function from spin echo small angle neutron scattering (SESANS) spectra. The accuracy of the simulation algorithm is tested with isolated hard spheres and single dumbbells consisting of two hard spheres separated by a given distance. The simulation results accurately reproduce the exact expressions of these two models. To further test the algorithm for many-body systems, two liquid models are considered including hard sphere fluids and hard spheres with an attractive tail. The many-particle Monte Carlo simulation is carried out to obtain the ensemble average of these correlation functions. Meanwhile, the Percus-Yevic (PY) integral equation theory is resorted to compute the autocorrelation function and SESANS spatial correlation function for a density that the PY theory is reasonably applicable. The agreement between simulation and theory indicates that the algorithm is quite robust and can be extended to more complex fluids in the future. Furthermore, we find that the SESANS spatial correlation function is highly sensitive to the interaction potential between particles, which may serve as a useful tool to explore particle interactions in a liquid.
我们开发了一种蒙特卡罗算法，以计算液体的自相关函数和相应的自旋回波小角中子散射（SESANS）谱的空间相关函数。我们使用孤立硬球和由给定距离分开的两个硬球组成的单个哑铃来测试模拟算法的准确性。模拟结果准确地再现了这两个模型的精确表达式。为了进一步测试该算法在多体系统中的适用性，我们考虑了两种液体模型，包括硬球流体和带有吸引力尾部的硬球。我们通过多粒子蒙特卡罗模拟获得这些相关函数的系综平均。同时，我们还求助于 Percus-Yevic (PY) 积分方程理论来计算 PY 理论合理适用的密度的自相关函数和 SESANS 空间相关函数。模拟和理论之间的一致性表明，该算法非常稳健，将来可以扩展到更复杂的流体。此外，我们发现 SESANS 空间相关函数对粒子之间的相互作用势非常敏感，这可能成为探索液体中粒子相互作用的有用工具。
