Schröder C, Rudas T, Neumayr G, Gansterer W, Steinhauser O
Department of Computational Biological Chemistry, University of Vienna, A-1090 Vienna, Austria.
J Chem Phys. 2007 Jul 28;127(4):044505. doi: 10.1063/1.2754690.
The complex ionic network of 1-butyl-3-methyl-imidazolium trifluoroacetate was simulated by means of the molecular dynamics methods over a time period of 100 ns. The influence of the anisotropy of the shape and charge distribution of both the cations and the anions on the local (molecular) and global (collective) structure and dynamics is analyzed. The distance-dependent g coefficients of the orientational probability function g(r,Omega) were found to be an excellent way to interpret local structure. Thereby, the combination and interrelation of individual g coefficients elucidate the mutual orientation. Dynamics at the molecular level is characterized by the time correlation function of the center-of-mass corrected molecular dipole moment mucm. Upon uniting the set of molecular dipoles to a single collective rotational dipole moment, MD, dynamics on a global level is studied. Decomposing into subsets of cations and anions respective self terms as well as the prominent cross term can be extracted. This decomposition also enables a detailed peak assignment in dielectric spectra.
采用分子动力学方法，在100纳秒的时间段内对1-丁基-3-甲基咪唑三氟乙酸盐的复杂离子网络进行了模拟。分析了阳离子和阴离子的形状及电荷分布的各向异性对局部（分子）和全局（集体）结构及动力学的影响。发现取向概率函数g(r,Ω)的距离相关g系数是解释局部结构的一种极佳方式。由此，各个g系数的组合及相互关系阐明了相互取向。分子水平的动力学由质心校正分子偶极矩mucm的时间相关函数表征。将分子偶极子集合合并为单个集体旋转偶极矩MD后，研究了全局水平的动力学。分解为阳离子和阴离子各自的自项以及突出的交叉项的子集后，可以提取出来。这种分解还能在介电谱中进行详细的峰归属。
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