Comparison of 2D melting criteria in a colloidal system
Comparison of 2D melting criteria in a colloidal system
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胶体系统中二维熔化标准的比较
DOI：
10.1088/0953-8984/24/46/464118
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
P. Keim
中科院分区：
文献类型：
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作者：
P. Dillmann;G. Maret;P. Keim
我们使用在水/空气界面上排列成二维单分子膜的超顺磁性球形粒子来研究晶体到液体的相变。根据KTHNY理论，晶体在热平衡状态下熔化，通过两个连续的相变进入具有中间相的各向同性液体状态，通常称为六相。对于相同的实验数据，我们验证了基于动力学和结构性质的几个判据对识别晶体-六元和六元-各向同性液体相变的重要性。这些判据包括键取向关联函数、拉尔森-格里尔判据、二维动态林德曼参数、键取向极化率、二维Hansen-Verlet判据、Löwen-Palberg-Simon判据以及基于Voronoi晶胞形状因子和Minkowski泛函的判据。对于具有长程斥力的体系，键级关联函数和键序极化率最适合于识别六向各向同性的液体转变，而二维动态林德曼参数明确地识别了六向各向同性的液体转变。
We use super-paramagnetic spherical particles which are arranged in a two-dimensional monolayer at a water/air interface to investigate the crystal to liquid phase transition. According to the KTHNY theory a crystal melts in thermal equilibrium by two continuous phase transitions into the isotropic liquid state with an intermediate phase, commonly known as the hexatic phase. We verify the significance of several criteria based on dynamical and structural properties to identify the crystal–hexatic and hexatic–isotropic liquid phase transitions for the same experimental data of the given setup. The criteria are the bond orientational correlation function, the Larson–Grier criterion, the 2D dynamic Lindemann parameter, the bond orientational susceptibility, the 2D Hansen–Verlet rule, the Löwen–Palberg–Simon criterion as well as a criterion based on the shape factor of Voronoi cells and Minkowski functionals. For our system with long-range repulsion, the bond order correlation function and bond order susceptibility work best to identify the hexatic–isotropic liquid transition and the 2D dynamic Lindemann parameter identifies unambiguously the hexatic–crystalline transition.