Yurchenko Stanislav O, Kryuchkov Nikita P, Ivlev Alexei V
Bauman Moscow State Technical University, 2nd Baumanskaya str. 5, 105005 Moscow, Russia.
J Phys Condens Matter. 2016 Jun 15;28(23):235401. doi: 10.1088/0953-8984/28/23/235401. Epub 2016 May 9.
Effects of anharmonicity on the pair correlation function of classical crystals are studied. The recently proposed shortest-graph approach using the Gaussian representation of the individual correlation peaks (the peak width is determined by the length of the shortest graph connecting a given pair of particles) is further improved, to account for anharmonic corrections due to finite temperatures and hard-sphere-like interactions. Two major effects are identified, leading to a modification of the correlation peaks at large or short distances: (i) the peaks at large distances, well described by Gaussians, should be calculated from the finite-temperature phonon spectra; (ii) at short distances, the correlation peaks deviate significantly from the Gaussian form due to the lattice discreteness. We propose the analytical interpolation method, based on the shortest-graph approach, which includes both effects. By employing the molecular dynamics simulations, the accuracy of the method is verified for three- and two-dimensional crystals with the Yukawa, inverse-power-law, and pseudo-hard-sphere pair interactions. The capabilities of the method are demonstrated by calculating the phase diagram of a three-dimensional Yukawa system.
研究了非简谐性对经典晶体对关联函数的影响。最近提出的使用单个关联峰的高斯表示的最短图方法（峰宽由连接给定粒子对的最短图的长度确定）得到了进一步改进，以考虑有限温度和类硬球相互作用引起的非简谐修正。确定了两个主要影响，导致大距离或短距离处关联峰的修改：（i）大距离处由高斯很好描述的峰，应根据有限温度声子谱计算；（ii）在短距离处，由于晶格离散性，关联峰显著偏离高斯形式。我们基于最短图方法提出了分析插值方法，该方法包括这两种影响。通过分子动力学模拟，验证了该方法对于具有 Yukawa、逆幂律和伪硬球对相互作用的三维和二维晶体的准确性。通过计算三维 Yukawa 系统的相图展示了该方法的能力。
