Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, Netherlands.
Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay, 91405 Orsay, France.
Phys Rev Lett. 2018 Dec 21;121(25):258001. doi: 10.1103/PhysRevLett.121.258001.
Vacancies in simple cubic crystals of hard cubes are known to delocalize over one-dimensional chains of several lattice sites. Here, we use computer simulations to examine the structure and dynamics of vacancies in simple cubic crystals formed by hard cubes, right rhombic prisms (slanted cubes), truncated cubes, and particles interacting via a soft isotropic pair potential. We show that these vacancies form a vacancy analog of the crowdion interstitial, generating a strain field which follows a soliton solution of the sine-Gordon equation, and diffusing via a persistent random walk. Surprisingly, we find that the structure of these "voidions" is not significantly affected by changes in density, vacancy concentration, and even particle interaction. We explain this structure quantitatively using a one-dimensional model that includes the free-energy barrier particles have to overcome to slide between lattice sites and the effective pair interaction along this line. We argue that voidions are a robust phenomenon in systems of repulsive particles forming simple cubic crystals.
已知硬立方形成的简单立方晶体中的空位会在几个晶格位置的一维链上离域。在这里，我们使用计算机模拟来研究由硬立方、右斜方棱柱（倾斜立方）、截角立方和通过软各向同性对势能相互作用的粒子形成的简单立方晶体中的空位的结构和动力学。我们表明，这些空位形成了拥挤间隙原子的空位类似物，产生了遵循正弦-戈登方程孤子解的应变场，并通过持续的随机漫步扩散。令人惊讶的是，我们发现这些“空穴离子”的结构不受密度、空位浓度甚至粒子相互作用的变化的显著影响。我们使用包括粒子在晶格位置之间滑动时必须克服的自由能势垒以及沿此线的有效对相互作用的一维模型来定量解释这种结构。我们认为，空穴离子是形成简单立方晶体的排斥粒子系统中的一个稳健现象。
