Department of Computational Biological Chemistry, University of Vienna, Wien A-1090, Austria.
J Chem Phys. 2010 Jun 28;132(24):244109. doi: 10.1063/1.3432620.
This work deals with the development of an appropriate set of fit functions for describing dielectric spectra based on simulated raw data. All these fit functions are of exponential character with properly chosen cofunctions. The type of the cofunctions is different for translation, rotation and their coupling. As an alternative to multiexponential fits we also discuss Kohlrausch-Williams-Watts functions. Since the corresponding Fourier-Laplace series for these stretched exponentials has severe convergence problems, we represent their Fourier-Laplace spectrum as a Havriliak-Negami expression with properly chosen parameters. A general relation between the parameter of the Kohlrausch-Williams-Watts and the Havriliak-Negami parameters is given. The set of fit functions is applied to the concrete simulation of the hydrated ionic liquid 1-ethyl-3-methyl-imidazolium triflate with H(2)O. The systematic variation of the water mole fraction permits to study the gradual transition from a neutral molecular liquid to molecular ionic liquids.
这项工作涉及开发一套合适的拟合函数，用于根据模拟原始数据描述介电谱。所有这些拟合函数都具有指数特征，并带有适当选择的余函数。对于平移、旋转及其耦合，余函数的类型不同。作为多指数拟合的替代方法，我们还讨论了 Kohlrausch-Williams-Watts 函数。由于这些扩展指数的相应 Fourier-Laplace 级数存在严重的收敛问题，我们将它们的 Fourier-Laplace 谱表示为具有适当选择参数的 Havriliak-Negami 表达式。给出了 Kohlrausch-Williams-Watts 参数与 Havriliak-Negami 参数之间的一般关系。该拟合函数集应用于水合离子液体 1-乙基-3-甲基-咪唑𬭩三氟甲磺酸酯与 H2O 的具体模拟。水摩尔分数的系统变化允许研究从中性分子液体到分子离子液体的逐渐转变。
