Hazra Anirban, Skone Jonathan H, Hammes-Schiffer Sharon
Department of Chemistry, 104 Chemistry Building, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
J Chem Phys. 2009 Feb 7;130(5):054108. doi: 10.1063/1.3068526.
The nuclear-electronic orbital (NEO) method is combined with vibronic coupling theory to calculate hydrogen tunneling splittings in polyatomic molecules. In this NEO-vibronic coupling approach, the transferring proton and all electrons are treated quantum mechanically at the NEO level, and the other nuclei are treated quantum mechanically using vibronic coupling theory. The dynamics of the molecule are described by a vibronic Hamiltonian in a diabatic basis of two localized nuclear-electronic states for the electrons and transferring proton. This ab initio approach is computationally practical and efficient for relatively large molecules, and the accuracy can be improved systematically. The NEO-vibronic coupling approach is used to calculate the hydrogen tunneling splitting for malonaldehyde. The calculated tunneling splitting of 24.5 cm(-1) is in excellent agreement with the experimental value of 21.6 cm(-1). This approach also enables the identification of the dominant modes coupled to the transferring hydrogen motion and provides insight into their roles in the hydrogen tunneling process.
核电子轨道（NEO）方法与振子-电子耦合理论相结合，用于计算多原子分子中的氢隧穿分裂。在这种NEO-振子-电子耦合方法中，转移质子和所有电子在NEO水平上进行量子力学处理，其他原子核则使用振子-电子耦合理论进行量子力学处理。分子的动力学由一个振子-电子哈密顿量描述，该哈密顿量基于电子和转移质子的两个局域核电子态的非绝热基。这种从头算方法对于相对较大的分子在计算上是实用且高效的，并且精度可以系统地提高。NEO-振子-电子耦合方法用于计算丙二醛的氢隧穿分裂。计算得到的24.5 cm⁻¹的隧穿分裂与21.6 cm⁻¹的实验值非常吻合。这种方法还能够识别与转移氢运动耦合的主导模式，并深入了解它们在氢隧穿过程中的作用。
