Begušić Tomislav, 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 Lett. 2021 Mar 25;12(11):2997-3005. doi: 10.1021/acs.jpclett.1c00123. Epub 2021 Mar 18.
Accurate description of finite-temperature vibrational dynamics is indispensable in the computation of two-dimensional electronic spectra. Such simulations are often based on the density matrix evolution, statistical averaging of initial vibrational states, or approximate classical or semiclassical limits. While many practical approaches exist, they are often of limited accuracy and difficult to interpret. Here, we use the concept of thermo-field dynamics to derive an exact finite-temperature expression that lends itself to an intuitive wavepacket-based interpretation. Furthermore, an efficient method for computing finite-temperature two-dimensional spectra is obtained by combining the exact thermo-field dynamics approach with the thawed Gaussian approximation for the wavepacket dynamics, which is exact for any displaced, distorted, and Duschinsky-rotated harmonic potential but also accounts partially for anharmonicity effects in general potentials. Using this new method, we directly relate a symmetry breaking of the two-dimensional signal to the deviation from the conventional Brownian oscillator picture.
在二维电子光谱的计算中，准确描述有限温度下的振动动力学是必不可少的。此类模拟通常基于密度矩阵演化、初始振动态的统计平均，或近似经典或半经典极限。虽然存在许多实用方法，但它们的精度往往有限且难以解释。在此，我们利用热场动力学的概念推导出一个精确的有限温度表达式，该表达式便于基于波包进行直观解释。此外，通过将精确的热场动力学方法与波包动力学的解冻高斯近似相结合，获得了一种计算有限温度二维光谱的有效方法，该近似对于任何位移、扭曲和杜施insky旋转的谐振势都是精确的，但也能部分考虑一般势中的非谐效应。使用这种新方法，我们直接将二维信号的对称性破缺与偏离传统布朗振子图像联系起来。
