This paper presents a numerical study of the asymmetric dumbbell model consisting of ``molecules'' constructed as two different Lennard-Jones spheres connected by a rigid bond. In terms of the largest (A) particle radius, we report data for the structure and dynamics of the liquid phase for the bond lengths 0.05, 0.1, 0.2, and 0.5, and analogous data for the plastic crystalline phase for the bond lengths 0.05, 0.1, 0.2, and 0.3. Structure is probed by means of the AA, AB, and BB radial distribution functions. Dynamics is probed via the A and B particle mean-square displacement as functions of time and via the rotational time-autocorrelation function. Consistent with the systems' strong virial potential-energy correlations, the structure and dynamics are both found to be isomorph invariant to a good approximation in reduced units, while they generally vary considerably along isotherms of the same (20%) density variation. Our findings provide the first validation of isomorph-theory predictions for plastic crystals for which isomorph invariance, in fact, is found to apply even better than in the liquid phase of asymmetric dumbbells.

中文翻译：

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非对称哑铃模型液相和塑晶相的同晶不变性

本文介绍了由“分子”组成的不对称哑铃模型的数值研究，这些“分子”由两个不同的 Lennard-Jones 球体通过刚性键连接而成。就最大 (A) 粒子半径而言，我们报告了键长 0.05、0.1、0.2 和 0.5 的液相结构和动力学数据，以及键长 0.05 的塑料结晶相的类似数据， 0.1、0.2 和 0.3。通过 AA、AB 和 BB 径向分布函数探测结构。通过作为时间函数的 A 和 B 粒子均方位移以及通过旋转时间自相关函数来探索动力学。与系统强大的维里势能相关性一致，结构和动力学都被发现是同构不变的，可以很好地近似于简化单位，而它们通常沿着相同（20％）密度变化的等温线变化很大。我们的研究结果首次验证了塑料晶体的同晶型理论预测，实际上发现同晶型不变性比在不对称哑铃的液相中更适用。