Wehrle Marius, Oberli Solène, Vaníček Jiří
Laboratory of Theoretical Physical Chemistry, Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
J Phys Chem A. 2015 Jun 4;119(22):5685-90. doi: 10.1021/acs.jpca.5b03907. Epub 2015 May 14.
We investigate the performance of on-the-fly ab initio (OTF-AI) semiclassical dynamics combined with the thawed Gaussian approximation (TGA) for computing vibrationally resolved absorption and photoelectron spectra. Ammonia is used as a prototype of floppy molecules, whose potential energy surfaces display strong anharmonicity. We show that despite complications due to the presence of large amplitude motion, the main features of the spectra are captured by the OTF-AI-TGA, which—by definition—does not require any a priori knowledge of the potential energy surface. Moreover, the computed spectra are significantly better than those based on the popular global harmonic approximation. Finally, we probe the limit of the TGA to describe higher-resolution spectra, where long time dynamics is required.
我们研究了即时从头算（OTF-AI）半经典动力学与解冻高斯近似（TGA）相结合用于计算振动分辨吸收光谱和光电子能谱的性能。氨被用作软分子的原型，其势能面表现出很强的非谐性。我们表明，尽管由于存在大幅度运动而带来了复杂性，但光谱的主要特征仍被OTF-AI-TGA捕捉到，根据定义，OTF-AI-TGA不需要任何关于势能面的先验知识。此外，计算得到的光谱明显优于基于流行的全局谐波近似得到的光谱。最后，我们探究了TGA描述更高分辨率光谱的极限，在这种情况下需要长时间动力学。
