论文标题
解冻的高斯波袋动力学适用于具有双孔势能表面的分子振动光谱的计算
Applicability of the thawed Gaussian wavepacket dynamics to the calculation of vibronic spectra of molecules with double-well potential energy surfaces
论文作者
论文摘要
模拟Anharmonic系统的振动分辨的电子光谱，尤其是涉及双孔势能表面的振动，通常需要昂贵的量子动力学方法。在这里，我们探讨了最近提出的单人融化的高斯近似值的适用性和局限性，以模拟具有双孔电势的系统的模拟，包括1,2,4,5-二氟氟苯，氨，磷素，磷酸和砷。与常规的谐波近似相比，这种半古老的波袋方法显示出更强的稳定性和更准确的光谱。具体而言，我们确定了两种情况，其中高斯波袋方法特别有用，这是由于谐波近似的分解：（i）当核波袋最初处于潜在障碍的顶部，但在两个井上的井中，例如，在低频模式下，沿两个井的井中都具有低频的能量，并且（ii）在波袋上具有足够的经典能量孔，并且两次都可以连接到两个井的能量。该方法是有效的，除了计算谐波光谱所需的数据外，仅需要单个经典的从头算分子动力学轨迹。我们还提出了一种用于计算波袋自相关函数的改进算法，该算法确保评估的相关函数对于时间步的任意大小是连续的。
Simulating vibrationally resolved electronic spectra of anharmonic systems, especially those involving double-well potential energy surfaces, often requires expensive quantum dynamics methods. Here, we explore the applicability and limitations of the recently proposed single-Hessian thawed Gaussian approximation for the simulation of spectra of systems with double-well potentials, including 1,2,4,5-tetrafluorobenzene, ammonia, phosphine, and arsine. This semiclassical wavepacket approach is shown to be more robust and to provide more accurate spectra than the conventional harmonic approximation. Specifically, we identify two cases in which the Gaussian wavepacket method is especially useful due to the breakdown of the harmonic approximation: (i) when the nuclear wavepacket is initially at the top of the potential barrier but delocalized over both wells, e.g., along a low-frequency mode, and (ii) when the wavepacket has enough energy to classically go over the low potential energy barrier connecting the two wells. The method is efficient and requires only a single classical ab initio molecular dynamics trajectory, in addition to the data required to compute the harmonic spectra. We also present an improved algorithm for computing the wavepacket autocorrelation function, which guarantees that the evaluated correlation function is continuous for arbitrary size of the time step.
