School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
J Phys Chem A. 2010 Mar 11;114(9):3096-102. doi: 10.1021/jp9082689.
Theoretical and experimental methods were integrated to investigate the structures of H(+)(CH(3)OH)(m)(H(2)O)(n) clusters for m + n = 5 and 6. An effective theoretical approach is presented to search for extensive sets of structural isomers using an empirical model and substitution schemes. Stable isomers were then reoptimized by the B3LYP level of computations with the 6-31+G* basis set. Canonical averages of these structural isomers were analyzed by harmonic superposition approximation (HSA) to study their finite temperature behavior and enable quantitative comparisons with experimental results. Thermal energy is found to have a significant effect on the structure of these clusters. Our calculations show that cyclic isomers are preferred at low temperature, while linear and tree forms become more favorable at high temperature (>200 K). Furthermore, we found that proton can reside on both water and methanol ion cores and the proton switch is associated with morphology change. Experimental IR spectra in the free OH stretching region were also obtained and compared with calculated spectra.
理论和实验方法相结合，研究了 H(+)(CH(3)OH)(m)(H(2)O)(n) 簇合物的结构，其中 m + n = 5 和 6。提出了一种有效的理论方法，使用经验模型和取代方案搜索广泛的结构异构体集。然后，通过 B3LYP 水平的计算和 6-31+G*基组对稳定的异构体进行重新优化。通过谐波叠加近似（HSA）对这些结构异构体的正则平均值进行分析，以研究它们的有限温度行为，并与实验结果进行定量比较。发现热能对这些簇合物的结构有显著影响。我们的计算表明，在低温下，环状异构体是优先的，而在高温（>200 K）下，线性和树状形式更为有利。此外，我们发现质子可以存在于水和甲醇离子核上，并且质子的转换与形态变化有关。还获得了游离 OH 伸缩区域的实验红外光谱，并与计算光谱进行了比较。
