Aix Marseille University, CNRS, PIIM, Marseille, France.
Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), Oberpfaffenhofen, Germany.
Sci Rep. 2017 Aug 11;7(1):7985. doi: 10.1038/s41598-017-08429-5.
We study collective modes in a classical system of particles with repulsive inverse-power-law (IPL) interactions in the fluid phase, near the fluid-solid coexistence (IPL melts). The IPL exponent is varied from n = 10 to n = 100 to mimic the transition from moderately soft to hard-sphere-like interactions. We compare the longitudinal dispersion relations obtained using molecular dynamic (MD) simulations with those calculated using the quasi-crystalline approximation (QCA) and find that this simple theoretical approach becomes grossly inaccurate for [Formula: see text]. Similarly, conventional expressions for high-frequency (instantaneous) elastic moduli, predicting their divergence as n increases, are meaningless in this regime. Relations of the longitudinal and transverse elastic velocities of the QCA model to the adiabatic sound velocity, measured in MD simulations, are discussed for the regime where QCA is applicable. Two potentially useful freezing indicators for classical particle systems with steep repulsive interactions are discussed.
我们研究了在接近固液共存（IPL 熔体）的流体相中，具有排斥性反幂律（IPL）相互作用的经典粒子系统中的集体模式。通过改变 IPL 指数 n = 10 到 n = 100，模拟了从中等软相互作用到硬球相似相互作用的转变。我们将使用分子动力学（MD）模拟得到的纵向弥散关系与使用准晶近似（QCA）计算得到的结果进行了比较，发现对于 IPL 熔体，这种简单的理论方法变得非常不准确。同样，对于高频（瞬时）弹性模量的常规表达式，预测它们随着 n 的增加而发散，在这个区域是没有意义的。讨论了在 QCA 适用的区域，QCA 模型的纵向和横向弹性速度与 MD 模拟中测量的绝热声速之间的关系。对于具有陡峭排斥相互作用的经典粒子系统，讨论了两种潜在有用的冻结指标。
