Molecular Dynamics Study of Thermodynamic Scaling of the Glass-Transition Dynamics in Ionic Liquids over Wide Temperature and Pressure Ranges
Molecular Dynamics Study of Thermodynamic Scaling of the Glass-Transition Dynamics in Ionic Liquids over Wide Temperature and Pressure Ranges
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DOI：
10.1021/jp911157k
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发表时间：
2010-03-25
影响因子：
3.3
通讯作者：
Ngai, K. L.
中科院分区：
文献类型：
--
作者：
Habasaki, J.;Casalini, R.;Ngai, K. L.
实验上，在不同温度 T、压力 P 和体积 V 条件下，通过缩放变量 TV gamma（其中 gamma 是材料常数）叠加动态特性，如粘度、弛豫时间或扩散系数，已被报道为多种玻璃形成材料的一般特征。在目前的工作中，进行了分子动力学（MD）模拟来研究离子液体玻璃化转变区域附近的动力学尺度。 Scaling ill file 模拟 1-乙基-3-甲基咪唑硝酸盐 (EMIM-NO3) 系统已在广泛的温度和压力范围内进行了测试。动态的 TV 缩放可以通过主曲线很好地描述，其中阳离子和阴离子的 gamma = 4.0 +/- 0.2 和 3.8 +/- 0.2。发现相应状态的结构和库仑项非常相似。成对相关函数的温度和压力依赖性显示出相似的趋势，因此需要叠加到主曲线上。尽管在关系 gamma = n/3 之前可以预期 gamma = 4 的行为，但对于软核型势 U = 11 = 12 的动力学，MD 模拟中使用的对势具有更复杂的形式，并且并非所有排斥项都能在由离子-离子相互作用决定的异质结构中发挥作用。缩放比例与与成对相关函数相关的有效势的公共部分有关，包括真实空间中的多体效应。
Experimentally, superpositioning of dynamic properties such as Viscosity, relaxation times, or diffusion coefficients Under different conditions of temperature T, pressure P, and volume V by the scaling variable TV gamma (where gamma is it material constant) has been reported as a general feature of many kinds of glass-forming materials. In the present work, molecular dynamics (MD) simulations have been performed to study the scaling of dynamics near the glass-transition regime of Ionic liquids. Scaling ill file simulated 1-ethyl-3-methylimidazolum nitrate (EMIM-NO3) system has been tested over wide ranges of temperatures and pressures. TV scaling of the dynamics is well described by master curves with gamma = 4.0 +/- 0.2 and 3.8 +/- 0.2 for cation and anion, respectively. structures and Coulombic terms of the corresponding states are found to be quite similar. The temperature and pressure dependence of the pair correlation function show similar trends and therefore call be superpositioned onto the master curve. Although the behaviors with gamma = 4 might be expected front the relation gamma = n/3, for the dynamics with the soft-core-type potential U = with 11 = 12, pair potentials Used in the MD simulation have a more complex form, and not all the repulsive terms can play their roles in the heterogeneous structures determined by ion-ion interactions. Scaling is related to the common part of effective potentials related to the pair correlation functions, including, the many-body effect in real space.