We investigate the phase behaviour of a system of particles interacting through the exp-6 pair potential, a model interaction that is appropriate to describe effective interatomic forces under high compression. The soft-repulsive component of the potential is being varied so as to study the effect on reentrant melting and density anomaly. Upon increasing the repulsion softness, we find that the anomalous melting features persist and occur at smaller pressures. Moreover, if we reduce the range of downward concavity in the potential by extending the hard core at the expenses of the soft-repulsive shoulder, the reentrant part of the melting line reduces in extent so as it does the region of density anomaly.
We consider binary suspension of rough, circular particles in two dimensions under athermal conditions. The mean density of the system is kept constant. The suspension is subject to a time-independent external drive in response to which one half of the particles are pulled along the field direction whereas the other half is pushed in the opposite direction. Simulating the system with different magnitude of external drive in steady state, we obtain oppositely moving macroscopic lanes only for a moderate range of external drive. Below as well as above the range we obtain states with no lane. Hen…
We report the first observation of temperature-controlled reentrant transition in simulations of mixtures of small and big particles interacting via soft repulsive potential in 2D. As temperature increases, the system passes from a fluid mixture, to a crystal of big particles in a fluid of small particles and back to a fluid mixture. Solidification is driven by entropy gain of small particles which overcomes the free energy cost of confining big ones. Melting results from enhanced interpenetration of particles at high temperature which reduces the entropic forces that stabilize the crystal.
The anomalous behavior of a two-dimensional system of Hertzian spheres with exponent $α= 7/2 $ has been studied using the method of molecular dynamics. The phase diagram of this system is the melting line of a triangular crystal with several maxima and minima. Water-like density and diffusion anomalies have been found in the reentrant melting regions. Noteworthy, a density anomaly has been observed not only in the liquid and hexatic but also solid phase. The calculations of the phonon spectra of longitudinal and transverse modes have yielded negative dependence of the frequency of transverse m…
Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses
我们研究了一个点粒子相互作用模型的结构和热力学性质，该模型是由Stillinger首次引入的高斯对势[Stillinger F H 1976 J. Chem. Phys. 65，3968]。利用流体状态的积分方程理论，通过与蒙特卡罗模拟结果的比较，确定了各种常用封闭的适用范围，并考察了液体的关联函数对密度和温度的依赖性。我们采用了一个简单的，平均场论的高密度域的液体，并表明，在无限密度的平均场论是准确的，该系统减少到一个“无限密度理想气体”，所有的相关性消失，超网链（HNC）关闭成为准确的。采用Einstein固相模型，定量计算了该模型的相图，发现该体系具有面心立方和体心立方两种固相，并在高密度下表现出重入熔融。此外，当温度超过相互作用强度的1%时，系统在所有密度下都保持流体状态。
