Theoretical vibrational spectra of OH-(H2O)2: Effect of quantum distribution and vibrational coupling
Theoretical vibrational spectra of OH-(H2O)2: Effect of quantum distribution and vibrational coupling
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OH-(H2O)2 的理论振动光谱：量子分布和振动耦合的影响
DOI：
10.1039/c5cp03632a
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
and M. Tachikawa
中科院分区：
文献类型：
--
作者：
Y. Ogata;Y. Kawashima;K. Takahashi;and M. Tachikawa
我们在50 K、100 K和150 K下对氢氧水团簇OH−（H2O）2进行了从头算路径积分分子动力学模拟，以研究其柔性结构。从我们的模拟中，我们发现核量子效应增强了氢氧化物氢原子的反转，并且通过自由氢原子的同时旋转发生异构体之间的构象变化。我们提出的重要性，包括过渡态构象与C2对称性，在预解离实验中实现的温度下，该系统的描述。利用各构象相对布居数的温度依赖性沿着与多维振动计算来模拟振动光谱，并与约翰逊及其同事的实验光谱进行比较。我们将实验中在2500 ~ 3000 cm-1处看到的双峰指定为离子氢键OH伸缩泛音、离子氢键OH弯曲泛音以及离子氢键OH伸缩和弯曲的组合带的混合物，它们由货车德瓦耳斯OO振动调制。我们的结论是，对于OH−（H2O）2，离子氢键运动和松弛模式之间的振动耦合有助于在2500至3000 cm−1区域观察到的峰的加宽。
We performed ab initio path integral molecular dynamics simulations for the hydroxide–water cluster, OH−(H2O)2, at 50 K, 100 K, and 150 K to investigate its flexible structure. From our simulations, we found that nuclear quantum effects enhance hydroxide hydrogen atom inversion and the conformational change between isomers occurs by simultaneous rotation of the free hydrogen atom. We propose the importance of including the transition state conformer with C2 symmetry, for the description of this system at temperatures realized in predissociation experiments. Temperature dependence of relative populations of each conformer along with multidimensional vibrational calculations were used to simulate the vibrational spectra and compare with the experimental spectra of Johnson and coworkers. We assign the doublet peaks seen in the experiment at 2500 to 3000 cm−1, as the mixture of the ionic hydrogen bonded OH stretching overtone, ionic hydrogen bonded OH bending overtone, and the combination band of the ionic hydrogen bonded OH stretch and bend, which are modulated by the van der Waals OO vibrations. We concluded that for OH−(H2O)2, the vibrational couplings between the ionic hydrogen bonded motion and floppy modes contribute to the broadening of peaks observed in the 2500 to 3000 cm−1 region.