论文标题
在有限温度下对振动光谱进行半经典评估
On-the-fly ab initio semiclassical evaluation of vibronic spectra at finite temperature
论文作者
论文摘要
为了在零温度下计算和分析振动分辨的电子光谱，我们最近实施了从头开始的延长融化的高斯近似[A. Patoz等人，J。Phys。化学Lett。 9，2367（2018）]，说明了非谐度，模式模式耦合和赫兹伯格 - 泰勒效果。在这里，我们概括了此方法，以评估在非零温度下的光谱。与热场动力学一致，我们将密度矩阵的相干成分的von Neumann演变转换为在增强空间中波函数的schrödinger演变，其自由度是两倍。由于扩展的融化高斯近似值的效率，坐标数量的增加几乎没有额外的计算成本。更具体地说，与原始的零温度方法相比，有限温度的方法不需要额外的缩写电子结构计算。同时，这种新方法可以在有限温度，非谐度和赫兹伯格 - 泰勒对光谱的影响之间明确区分。我们在模型摩尔斯系统上显示，有限温度的优势将高斯近似与常用的全局谐波方法相比，并将其应用于苯的对称性填充吸收光谱，在那里所有上述效应都会造成上述效果。
To compute and analyze vibrationally resolved electronic spectra at zero temperature, we have recently implemented the on-the-fly ab initio extended thawed Gaussian approximation [A. Patoz et al., J. Phys. Chem. Lett. 9, 2367 (2018)], which accounts for anharmonicity, mode-mode coupling, and Herzberg-Teller effects. Here, we generalize this method in order to evaluate spectra at non-zero temperature. In line with thermo-field dynamics, we transform the von Neumann evolution of the coherence component of the density matrix to the Schrödinger evolution of a wavefunction in an augmented space with twice as many degrees of freedom. Due to the efficiency of the extended thawed Gaussian approximation, this increase in the number of coordinates results in nearly no additional computational cost. More specifically, compared to the original, zero-temperature approach, the finite-temperature method requires no additional ab initio electronic structure calculations. At the same time, the new approach allows for a clear distinction among finite-temperature, anharmonicity, and Herzberg-Teller effects on spectra. We show, on a model Morse system, the advantages of the finite-temperature thawed Gaussian approximation over the commonly used global harmonic methods and apply it to evaluate the symmetry-forbidden absorption spectrum of benzene, where all of the aforementioned effects contribute.
