论文标题
使用一般的intanton路径的振动激发态的隧道分裂
Tunneling splittings of vibrationally excited states using general instanton paths
论文作者
论文摘要
开发了一种用于计算使用笛卡尔坐标的分子振动激发态中的隧道分裂的多维半经典方法。这是Mil'nikov和Nakamura [$ \ textit {J. Chem。 Phys。} $ $ \ textbf {122} $，$ 124311 $ $（2005）$]，用于计算多孔系统（例如水簇）中计算隧道分裂模式所必需的不对称路径。此外，在半经典波函数的描述中介绍了新术语，这些术语大大改善了某些系统的分裂估计值。该方法基于激体理论，并构建了沿最小动作路径及其谐波邻域的振动激发态的半经典波函数。因此，激发态的分裂是在可忽略不计的数值努力下获得的。对于地面分裂，成本是集中的，在instanton路径优化和沿路径的Hessian评估中。因此，该方法可以无需修改以完全维度的许多中大号分子的修改，并结合对电子电位的即时评估。对几个模型电位和水二聚体进行了测试。
A multidimensional semiclassical method for calculating tunneling splittings in vibrationally excited states of molecules using Cartesian coordinates is developed. It is an extension of the theory by Mil'nikov and Nakamura [$\textit{ J. Chem. Phys.}$ $\textbf{122}$, $124311$ $(2005)$] to asymmetric paths that are necessary for calculating tunneling splitting patterns in multi-well systems, such as water clusters. Additionally, new terms are introduced in the description of the semiclassical wavefunction that drastically improve the splitting estimates for certain systems. The method is based on the instanton theory and builds the semiclassical wavefunction of the vibrationally excited states from the ground-state instanton wavefunction along the minimum action path and its harmonic neighborhood. The splittings of excited states are thus obtained at a negligible added numerical effort. The cost is concentrated, as for the ground-state splittings, in the instanton path optimization and the hessian evaluation along the path. The method can thus be applied without modification to many mid-sized molecules in full dimensionality and in combination with on-the-fly evaluation of electronic potentials. The tests were performed on several model potentials and on the water dimer.
