Culpitt Tanner, Yang Yang, Pavošević Fabijan, Tao Zhen, Hammes-Schiffer Sharon
Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520 USA.
J Chem Phys. 2019 May 28;150(20):201101. doi: 10.1063/1.5099093.
The multicomponent extension of time-dependent density functional theory (TDDFT) within the nuclear-electronic orbital (NEO) framework enables the calculation of both electronic and vibrational excitations simultaneously. In this NEO-TDDFT approach, all electrons and select nuclei, typically protons, are treated quantum mechanically on the same level. Herein, the dependence of the proton vibrational excitation energies on the nuclear and electronic basis sets is examined. Protonic basis sets that include f basis functions in conjunction with substantial electronic basis sets for the quantum hydrogen are found to produce accurate proton vibrational excitation energies that are mostly within ∼30 cm of reference values for the molecules studied. The NEO-TDDFT approach is shown to be effective for open-shell as well as closed-shell systems. Additionally, an approach for computing and visualizing the nuclear transition densities associated with the proton vibrational excitations is implemented. These nuclear transition densities are important for characterizing the proton vibrational excitations and determining the spatial orientations of the corresponding vibrational modes. These capabilities are essential for a variety of applications, including the incorporation of anharmonic effects into molecular vibrational frequency calculations.
在核电子轨道（NEO）框架内，含时密度泛函理论（TDDFT）的多组分扩展能够同时计算电子激发和振动激发。在这种NEO-TDDFT方法中，所有电子和选定的原子核（通常是质子）都在同一水平上进行量子力学处理。在此，研究了质子振动激发能对核基组和电子基组的依赖性。发现对于量子氢而言，包含f基函数并结合大量电子基组的质子基组能够产生精确的质子振动激发能，对于所研究的分子，这些能量大多在参考值的约30厘米范围内。结果表明，NEO-TDDFT方法对开壳层和闭壳层系统均有效。此外，还实现了一种计算和可视化与质子振动激发相关的核跃迁密度的方法。这些核跃迁密度对于表征质子振动激发以及确定相应振动模式的空间取向非常重要。这些能力对于包括将非谐效应纳入分子振动频率计算在内的各种应用至关重要。
