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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Elementary Steps of Lithium Ion Transport in PEO via Quantum Mechanical Calculations
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Elementary Steps of Lithium Ion Transport in PEO via Quantum Mechanical Calculations

机译：量子力学计算中锂离子在PEO中传输的基本步骤

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摘要

A first attempt to model lithium ion transport along a poly(ethylene oxide), PEO, chain by quantum mechanical calculations is reported here. The PEO oligomer diglyme (CH_3O-(CH_2CH_2O)_2-CH_3) has been used as a model system for a PEO polymer. Different transition states have been calculated with ab initio methods for conformational changes leading to changes in coordination number for lithium from three to two in the lithium-diglyme complexes. The imaginary frequencies for the transition states and the associated intrinsic reaction-coordinate paths have been calculated. Energy barriers of ～90 kJ mol~(-1) are found along all the paths. The use of a bidentate structure as an intermediate between the two different tridentate structures is suggested. All structures have been optimized at the HF/6-31G~(**) level of theory, and the total energy calculations have been performed at different levels of sophistication (HF/6-31G~(**) and MP2/6-311 + G~(**)//HF/6-31G~(**)). Furthermore, two equivalent transition states for the next oligomer in size, triglyme, complexed with a lithium ion have been calculated to test and show the stability of the calculations of the present model when elongating the oligomer. The results are compared with NMR data for the activation energies of conformational transformations in complexed PEO. A transport path for Li~+ along a single PEO chain involving tri- to "tetra-" to tridentate coordination changes with small energy differences has been calculated.
机译：本文首次尝试通过量子力学计算来模拟锂离子沿聚环氧乙烷PEO链的迁移。 PEO低聚物二甘醇二甲醚（CH_3O-（CH_2CH_2O）_2-CH_3）已用作PEO聚合物的模型系统。从头算方法已经计算出不同的过渡态用于构象变化，从而导致锂-二甘醇二甲醚络合物中锂的配位数从三变为二。已经计算出过渡态和相关的固有反应坐标路径的虚数频率。在所有路径上都发现了〜90 kJ mol〜（-1）的能垒。建议使用双齿结构作为两个不同的三齿结构之间的中间产物。在HF / 6-31G〜（**）的理论水平上优化了所有结构，并且在不同的复杂程度（HF / 6-31G〜（**）和MP2 / 6-进行了总能量计算） 311 + G〜（**）// HF / 6-31G〜（**））。此外，已计算出与锂离子络合的下一个低聚物三甘醇二甲醚的两个等效过渡态，以测试并显示出当加长低聚物时本模型计算的稳定性。将结果与NMR数据进行比较，得出复合PEO中构象转化的活化能。已计算出Li〜+沿着一条PEO链的传输路径，该路径涉及从三到“四”到三齿的配位变化，并且能量差异很小。

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