Sharma Abhishek K, Escobedo Fernando A
R. F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, United States.
J Phys Chem B. 2021 May 20;125(19):5160-5170. doi: 10.1021/acs.jpcb.1c01737. Epub 2021 May 4.
Many hard faceted nanoparticles are known to undergo disorder-to-order phase transitions following a classical nucleation and growth mechanism. In a previous study [ , , 9264-9273], it was shown that hard cubes undergo a nonclassical phase transition with a bulk character instead of originating from consolidated nuclei. Significantly, an unusually high fraction of ordered particles was observed in the metastable basin of the disordered phase, even for very low degrees of supersaturation. This work aims to substantiate the conjecture that these unique properties originate from a comparatively low interfacial free energy between the disordered and ordered phases for hard cubes relative to other hard particle systems. Using the cleaving wall method to directly measure the interfacial free energy for cubes, it is found that its values are indeed small; e.g., at phase coexistence conditions, it is only one-fifth that for hard spheres. A theoretical nucleation model is used to explore the broader implications of low interfacial tension values and how this could result in a bulk ordering mechanism.
已知许多硬面纳米颗粒遵循经典的成核和生长机制经历从无序到有序的相变。在先前的一项研究[，，9264 - 9273]中，表明硬立方体经历了具有体相特征的非经典相变，而不是起源于固结的核。值得注意的是，即使在非常低的过饱和度下，在无序相的亚稳区内也观察到了异常高比例的有序颗粒。这项工作旨在证实这样的推测：相对于其他硬颗粒系统，这些独特的性质源于硬立方体无序相和有序相之间相对较低的界面自由能。使用劈裂壁法直接测量立方体的界面自由能，发现其值确实很小；例如，在相共存条件下，它仅为硬球的五分之一。使用理论成核模型来探索低界面张力值的更广泛影响以及这如何导致体相有序机制。
