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首页> 外文期刊>The Journal of Chemical Physics >Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water-dimer III: Mixed Jacobi-valence parametrization and benchmark results for the zero point energy, vibrationally excited states, and infrared spectrum
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Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water-dimer III: Mixed Jacobi-valence parametrization and benchmark results for the zero point energy, vibrationally excited states, and infrared spectrum

机译：质子化水二聚体III的全尺寸（15维）量子动力学模拟：混合雅可比价参数化和零点能量，振动激发态和红外光谱的基准结果

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摘要

Quantum dynamical calculations are reported for the zero point energy, several low-lying vibrational states, and the infrared spectrum of the H_5O_2~+ cation. The calculations are performed by the multiconfiguration time-dependent Hartree (MCTDH) method. A new vector parametrization based on a mixed Jacobi-valence description of the system is presented. With this parametrization the potential energy surface coupling is reduced with respect to a full Jacobi description, providing a better convergence of the n-mode representation of the potential. However, new coupling terms appear in the kinetic energy operator. These terms are derived and discussed. A mode-combination scheme based on six combined coordinates is used, and the representation of the 15-dimensional potential in terms of a six-combined mode cluster expansion including up to some 7-dimensional grids is discussed. A statistical analysis of the accuracy of the n-mode representation of the potential at all orders is performed. Benchmark, fully converged results are reported for the zero point energy, which lie within the statistical uncertainty of the reference diffusion Monte Carlo result for this system. Some low-lying vibrationally excited eigenstates are computed by block improved relaxation, illustrating the applicability of the approach to large systems. Benchmark calculations of the linear infrared spectrum are provided, and convergence with increasing size of the time-dependent basis and as a function of the order of the n-mode representation is studied. The calculations presented here make use of recent developments in the parallel version of the MCTDH code, which are briefly discussed. We also show that the infrared spectrum can be computed, to a very good approximation, within D_(2d) symmetry, instead of the G_(16) symmetry used before, in which the complete rotation of one water molecule with respect to the other is allowed, thus simplifying the dynamical problem.
机译：报告了零点能量，几个低振动态和H_5O_2〜+阳离子的红外光谱的量子动力学计算。通过多配置时变哈特里（MCTDH）方法执行计算。提出了一种基于系统混合雅可比价描述的新矢量参数化方法。通过这种参数化，相对于完整的Jacobi描述，势能表面耦合得以减少，从而提供了电势的n模式表示的更好收敛。但是，新的耦合项出现在动能算子中。这些术语是派生和讨论的。使用基于六个组合坐标的模式组合方案，并讨论了六维模式簇扩展中最多包含7维网格的15维势的表示形式。对所有阶次的电势的n模式表示的准确性进行统计分析。报告了零点能量的基准，完全收敛的结果，该结果在该系统的参考扩散蒙特卡洛结果的统计不确定性内。一些低洼的振动激发本征态是通过块改进的弛豫来计算的，说明了该方法在大型系统中的适用性。提供了线性红外光谱的基准计算，并且研究了随时间变化的基础的大小以及n模式表示的阶次函数的收敛性。此处介绍的计算利用了MCTDH代码并行版本中的最新进展，对此进行了简要讨论。我们还表明，可以在D_（2d）对称性内而不是之前使用的G_（16）对称性内，以非常好的近似值计算红外光谱，其中一个水分子相对于另一个分子的完整旋转是允许，从而简化了动力学问题。

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