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arXiv 0812.3390cond-mat.stat-mechcond-mat.soft
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基于优化关联函数的稠密球填充

Dense sphere packings from optimized correlation functions

Adam B. Hopkins, Frank H. Stillinger, Salvatore Torquato

摘要:

基本光滑函数(超越接触)被用来构造成对的关联函数,以模拟堵塞的无序球填充。使用Torquato和Stillinger [J. Phys. Chem. B 106,8354,2002]的g2不变优化方法,在必要的可实现性条件下优化这些函数中的参数,以最大化填充分数phi和每个球Z的平均接触数。一对关联函数,它包含了无序堆积的显著特征,并且在接触之外是光滑的,被示出为允许φ为0.6850:该值表示三维中全等硬球的最大值π/sqrt{18} ~ 0.7405,和0.64,与最大随机堵塞(MRJ)填料在三维空间中的近似分数。我们发现,令人惊讶的是,继续添加由光滑正弦曲线组成的初等函数,其衰减为r^{-4},允许填充分数接近pi/sqrt{18}。一个平移顺序度量是用来区分度的顺序包装。我们发现,为了获得更高的填充分数,有序度必须增加,这与先前研究的结果一致[Torquato等人,物理修订版信函84,2064,2000]。

英文摘要:

Elementary smooth functions (beyond contact) are employed to construct pair correlation functions that mimic jammed disordered sphere packings. Using the g2-invariant optimization method of Torquato and Stillinger [J. Phys. Chem. B 106, 8354, 2002], parameters in these functions are optimized under necessary realizability conditions to maximize the packing fraction phi and average number of contacts per sphere Z. A pair correlation function that incorporates the salient features of a disordered packing and that is smooth beyond contact is shown to permit a phi of 0.6850: this value represents a 45% reduction in the difference between the maximum for congruent hard spheres in three dimensions, pi/sqrt{18} ~ 0.7405, and 0.64, the approximate fraction associated with maximally random jammed (MRJ) packings in three dimensions. We show that, surprisingly, the continued addition of elementary functions consisting of smooth sinusoids decaying as r^{-4} permits packing fractions approaching pi/sqrt{18}. A translational order metric is used to discriminate between degrees of order in the packings presented. We find that to achieve higher packing fractions, the degree of order must increase, which is consistent with the results of a previous study [Torquato et al., Phys. Rev. Lett. 84, 2064, 2000].

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