Theoretical study of Raman spectra of methanol in aqueous solutions: non-coincident effect of the CO stretch.
Theoretical study of Raman spectra of methanol in aqueous solutions: non-coincident effect of the CO stretch.
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DOI：
10.1021/jp300178v
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发表时间：
2012-03
期刊：
影响因子：
--
通讯作者：
Yuanyuan Sun;Ren-hui Zheng;Qiang Shi
中科院分区：
文献类型：
--
作者：
Yuanyuan Sun;Ren-hui Zheng;Qiang Shi
用电子结构和分子动力学相结合的方法模拟了液态甲醇及其水溶液的CO拉曼光谱。瞬时振动频率由经验映射到静电势得到，而不同分子之间的振动耦合采用跃迁偶极耦合模型计算。结果表明，高浓度下的非符合效应(NCEs)主要由CO分子间的耦合作用决定，随着甲醇浓度的降低，NCEs单调减小。这一行为被解释为水的加入降低了甲醇-甲醇氢键的影响。由CO拉伸峰位置定义的NCEs随甲醇摩尔分数的变化是非单调的，这归因于重取向动力学引起的带不对称性。
Raman spectra of the CO stretch for liquid methanol and its aqueous solutions were simulated using the combined electronic structure and molecular dynamics simulation method. The instantaneous vibrational frequencies were obtained from an empirical mapping to the electrostatic potentials, while vibrational couplings between different molecules were calculated using the transition dipole coupling model. It is found that noncoincident effects (NCEs) at high concentrations are dominated by the intermolecular couplings of CO stretch and decrease monotonically as the methanol concentration decreases. This behavior is explained as the effect of reduced methanol-methanol hydrogen bonding with the addition of water. A non-monotonic change of the NCEs defined by the peak position of the CO stretch as a function of methanol mole fraction is found, which is ascribed to band asymmetry caused by reorientational dynamics.