Bernini S, Puosi F, Leporini D
Dipartimento di Fisica 'Enrico Fermi', Università di Pisa, Largo B Pontecorvo 3, I-56127 Pisa, Italy. Present address: Jawaharlal Nehru Center for Advanced Scientific Research, Theoretical Sciences Unit, Jakkur Campus, Bengaluru 560064, India.
J Phys Condens Matter. 2017 Apr 5;29(13):135101. doi: 10.1088/1361-648X/aa5a7e. Epub 2017 Jan 19.
Using molecular dynamics simulations of a molecular liquid, we investigate the thermodynamic scaling (TS) of the structural relaxation time [Formula: see text] in terms of the quantity [Formula: see text], where T and ρ are the temperature and density, respectively. The liquid does not exhibit strong virial-energy correlations. We propose a method for evaluating both the characteristic exponent [Formula: see text] and the TS master curve that uses experimentally accessible quantities that characterise the anharmonic elasticity and does not use details about the microscopic interactions. In particular, we express the TS characteristic exponent [Formula: see text] in terms of the lattice Grüneisen parameter [Formula: see text] and the isochoric anharmonicity [Formula: see text]. An analytic expression of the TS master curve of [Formula: see text] with [Formula: see text] as the key adjustable parameter is found. The comparison with the experimental TS master curves and the isochoric fragilities of 34 glassformers is satisfying. In a few cases, where thermodynamic data are available, we test (i) the predicted characteristic exponent [Formula: see text] and (ii) the isochoric anharmonicity [Formula: see text], as drawn by the best fit of the TS of the structural relaxation, against the available thermodynamic data. A linear relation between the isochoric fragility and the isochoric anharmonicity [Formula: see text] is found and compared favourably with the results of experiments with no adjustable parameters. A relation between the increase of the isochoric vibrational heat capacity due to anharmonicity and the isochoric fragility is derived.
通过对分子液体进行分子动力学模拟，我们依据量[公式：见正文]研究了结构弛豫时间[公式：见正文]的热力学标度（TS），其中T和ρ分别为温度和密度。该液体不表现出强维里能相关性。我们提出了一种评估特征指数[公式：见正文]和TS主曲线的方法，该方法使用可通过实验获取的表征非谐弹性的量，且不使用关于微观相互作用的细节。特别地，我们根据晶格格林艾森参数[公式：见正文]和等容非谐性[公式：见正文]来表示TS特征指数[公式：见正文]。找到了以[公式：见正文]作为关键可调参数的[公式：见正文]的TS主曲线的解析表达式。与34种玻璃形成体的实验TS主曲线和等容脆性的比较结果令人满意。在少数可获得热力学数据的情况下，我们针对可用的热力学数据测试：（i）预测的特征指数[公式：见正文]和（ii）通过结构弛豫的TS最佳拟合得出的等容非谐性[公式：见正文]。发现了等容脆性与等容非谐性[公式：见正文]之间的线性关系，且与无可调参数的实验结果相比表现良好。推导了由于非谐性导致的等容振动热容量增加与等容脆性之间的关系。
