Cazade Pierre-André, Tran Halina, Bereau Tristan, Das Akshaya K, Kläsi Felix, Hamm Peter, Meuwly Markus
Department of Chemistry, University of Basel, Klingelbergstrasse 80, 4056 Basel, Switzerland.
Department of Chemistry, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland.
J Chem Phys. 2015 Jun 7;142(21):212415. doi: 10.1063/1.4916630.
The solvent dynamics around fluorinated acetonitrile is characterized by 2-dimensional infrared spectroscopy and atomistic simulations. The lineshape of the linear infrared spectrum is better captured by semiempirical (density functional tight binding) mixed quantum mechanical/molecular mechanics simulations, whereas force field simulations with multipolar interactions yield lineshapes that are significantly too narrow. For the solvent dynamics, a relatively slow time scale of 2 ps is found from the experiments and supported by the mixed quantum mechanical/molecular mechanics simulations. With multipolar force fields fitted to the available thermodynamical data, the time scale is considerably faster--on the 0.5 ps time scale. The simulations provide evidence for a well established CF-HOH hydrogen bond (population of 25%) which is found from the radial distribution function g(r) from both, force field and quantum mechanics/molecular mechanics simulations.
通过二维红外光谱和原子模拟对含氟乙腈周围的溶剂动力学进行了表征。半经验（密度泛函紧束缚）混合量子力学/分子力学模拟能更好地捕捉线性红外光谱的线形，而具有多极相互作用的力场模拟产生的线形明显过窄。对于溶剂动力学，实验发现了相对较慢的2皮秒时间尺度，并得到了混合量子力学/分子力学模拟的支持。使用根据现有热力学数据拟合的多极力场，时间尺度要快得多——在0.5皮秒时间尺度上。模拟为一个已确立的CF-HOH氢键（占有率为25%）提供了证据，这是从力场和量子力学/分子力学模拟的径向分布函数g(r)中发现的。
