1
|
Sharma AK, Escobedo FA. Effect of particle anisotropy on the thermodynamics and kinetics of ordering transitions in hard faceted particles. J Chem Phys 2023; 158:044502. [PMID: 36725523 DOI: 10.1063/5.0135461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Monte Carlo simulations were used to study the influence of particle aspect ratio on the kinetics and phase behavior of hard gyrobifastigia (GBF). First, the formation of a highly anisotropic nucleus shape in the isotropic-to-crystal transition in regular GBF is explained by the differences in interfacial free energies of various crystal planes and the nucleus geometry predicted by the Wulff construction. GBF-related shapes with various aspect ratios were then studied, mapping their equations of state, determining phase coexistence conditions via interfacial pinning, and computing nucleation free-energy barriers via umbrella sampling using suitable order parameters. Our simulations reveal a reduction of the kinetic barrier for isotropic-crystal transition upon an increase in aspect ratio, and that for highly oblate and prolate aspect ratios, an intermediate nematic phase is stabilized. Our results and observations also support two conjectures for the formation of the crystalline state from the isotropic phase: that low phase free energies at the ordering phase transition correlate with low transition barriers and that the emergence of a mesophase provides a steppingstone that expedites crystallization.
Collapse
Affiliation(s)
- Abhishek K Sharma
- R. F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Fernando A Escobedo
- R. F. Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| |
Collapse
|
2
|
Ding Y, Yang J, Ou Y, Zhao Y, Li J, Hu B, Xia C. Structural evolution of granular cubes packing during shear-induced ordering. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:224003. [PMID: 35263715 DOI: 10.1088/1361-648x/ac5c22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 03/09/2022] [Indexed: 06/14/2023]
Abstract
Packings of granular particles may transform into ordered structures under external agitation, which is a special type of out-of-equilibrium self-assembly. Here, evolution of the internal packing structures of granular cubes under cyclic rotating shearing has been analyzed using magnetic resonance imaging techniques. Various order parameters, different types of contacts and clusters composed of face-contacting cubes, as well as the free volume regions in which each cube can move freely have been analyzed systematically to quantify the ordering process and the underlying mechanism of this granular self-assembly. The compaction process is featured by a first rapid formation of orientationally ordered local structures with faceted contacts, followed by further densification driven by free-volume maximization with an almost saturated degree of order. The ordered structures are strongly anisotropic with contacting ordered layers in the vertical direction while remaining liquid-like in the horizontal directions. Therefore, the constraint of mechanical stability for granular packings and the thermodynamic principle of entropy maximization are both effective in this system, which we propose can be reconciled by considering different depths of supercooling associated with various degrees of freedom.
Collapse
Affiliation(s)
- Yunhao Ding
- Shanghai Key Laboratory of Magnetic Resonance, Institute of Materials, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, People's Republic of China
| | - Jing Yang
- Shanghai Key Laboratory of Magnetic Resonance, Institute of Materials, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, People's Republic of China
| | - Yao Ou
- Shanghai Key Laboratory of Magnetic Resonance, Institute of Materials, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, People's Republic of China
| | - Yu Zhao
- Shanghai Key Laboratory of Magnetic Resonance, Institute of Materials, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, People's Republic of China
| | - Jianqi Li
- Shanghai Key Laboratory of Magnetic Resonance, Institute of Materials, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, People's Republic of China
| | - Bingwen Hu
- Shanghai Key Laboratory of Magnetic Resonance, Institute of Materials, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, People's Republic of China
| | - Chengjie Xia
- Shanghai Key Laboratory of Magnetic Resonance, Institute of Materials, School of Physics and Electronic Science, East China Normal University, Shanghai 200241, People's Republic of China
| |
Collapse
|