Departamento de Física Teórica de la Materia Condensada, Instituto de Física de la Materia Condensada (IFIMAC), Instituto de Ciencias de Materiales "Nicolás Cabrera," Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, E-28049 Madrid, Spain.
Department of Chemistry and Department of Physics, Institute for the Science and Technology of Materials, Program for Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544, USA.
Phys Rev E. 2019 Dec;100(6-1):062902. doi: 10.1103/PhysRevE.100.062902.
Among the family of hard convex lens-shaped particles (lenses), the one with aspect ratio equal to 2/3 is "optimal" in the sense that the maximally random jammed (MRJ) packings of such lenses achieve the highest packing fraction ϕ_{MRJ}≃0.73 [G. Cinacchi and S. Torquato, Soft Matter 14, 8205 (2018)1744-683X10.1039/C8SM01519H]. This value is only a few percent lower than ϕ_{DKP}=0.76210⋯, the packing fraction of the corresponding densest-known crystalline (degenerate) packings [G. Cinacchi and S. Torquato, J. Chem. Phys. 143, 224506 (2015)JCPSA60021-960610.1063/1.4936938]. By exploiting the appreciably reduced propensity that a system of such optimal lenses has to positionally and orientationally order, disordered packings of them are progressively generated by a Monte Carlo method-based procedure from the dilute equilibrium isotropic fluid phase to the dense nonequilibrium MRJ state. This allows us to closely monitor how the (micro)structure of these packings changes in the process of formation of the MRJ state. The gradual changes undergone by the many structural descriptors calculated here can coherently and consistently be traced back to the gradual increase in contacts between the hard particles until the isostatic mean value of ten contact neighbors per lens is reached at the effectively hyperuniform MRJ state. Compared to the MRJ state of hard spheres, the MRJ state of such optimal lenses is denser (less porous), more disordered, and rattler-free. This set of characteristics makes them good glass formers. It is possible that this conclusion may also hold for other hard convex uniaxial particles with a correspondingly similar aspect ratio, be they oblate or prolate, and that, by using suitable biaxial variants of them, that set of characteristics might further improve.
在硬凸面透镜状颗粒（透镜）家族中，具有 2/3 纵横比的透镜在最大随机堆积（MRJ）中达到最高堆积分数ϕ_{MRJ}≃0.73 [G. Cinacchi 和 S. Torquato，Soft Matter 14, 8205 (2018)1744-683X10.1039/C8SM01519H]，这具有“最优”意义。这个值仅比相应的最密已知晶体（简并）堆积ϕ_{DKP}=0.76210⋯低几个百分点[G. Cinacchi 和 S. Torquato，J. Chem. Phys. 143, 224506 (2015)JCPSA60021-960610.1063/1.4936938]。通过利用系统中这种最优透镜具有位置和方向有序的倾向大大降低，通过基于蒙特卡罗方法的程序，从稀平衡各向同性流体相到密集非平衡 MRJ 状态，逐步生成它们的无序堆积。这使我们能够密切监控这些堆积物的结构如何在形成 MRJ 状态的过程中发生变化。通过计算这里的许多结构描述符，可以清楚地追溯到硬颗粒之间接触的逐渐增加，直到有效超均匀的 MRJ 状态下每透镜达到十个接触邻居的等静压平均值。与硬球的 MRJ 状态相比，这种最优透镜的 MRJ 状态更加致密（多孔性更低）、更加无序且没有 rattler。这组特性使它们成为良好的玻璃形成体。对于其他具有相应相似纵横比的硬凸单轴颗粒，无论是扁长形还是长扁形，可能也存在同样的结论，并且通过使用它们的合适双轴变体，可能进一步改善该组特性。
