Han Huixian, Li Anyang, Guo Hua
Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
J Chem Phys. 2014 Dec 28;141(24):244312. doi: 10.1063/1.4904859.
A new full-dimensional global potential energy surface (PES) for the acetylene-vinylidene isomerization on the ground (S0) electronic state has been constructed by fitting ∼37,000 high-level ab initio points using the permutation invariant polynomial-neural network method with a root mean square error of 9.54 cm(-1). The geometries and harmonic vibrational frequencies of acetylene, vinylidene, and all other stationary points (two distinct transition states and one secondary minimum in between) have been determined on this PES. Furthermore, acetylene vibrational energy levels have been calculated using the Lanczos algorithm with an exact (J = 0) Hamiltonian. The vibrational energies up to 12,700 cm(-1) above the zero-point energy are in excellent agreement with the experimentally derived effective Hamiltonians, suggesting that the PES is approaching spectroscopic accuracy. In addition, analyses of the wavefunctions confirm the experimentally observed emergence of the local bending and counter-rotational modes in the highly excited bending vibrational states. The reproduction of the experimentally derived effective Hamiltonians for highly excited bending states signals the coming of age for the ab initio based PES, which can now be trusted for studying the isomerization reaction.
通过使用置换不变多项式神经网络方法拟合约37000个高水平从头算点，构建了一个新的基态（S0）电子态乙炔-亚乙烯基异构化的全维全局势能面（PES），其均方根误差为9.54 cm(-1)。在此PES上确定了乙炔、亚乙烯基以及所有其他驻点（两个不同的过渡态和其间的一个二级极小值）的几何结构和谐波振动频率。此外，使用具有精确（J = 0）哈密顿量的兰索斯算法计算了乙炔的振动能级。高于零点能达12700 cm(-1)的振动能量与实验推导的有效哈密顿量高度吻合，这表明该PES已接近光谱精度。此外，波函数分析证实了在高激发弯曲振动状态下实验观察到的局部弯曲和反向旋转模式的出现。对高激发弯曲态实验推导的有效哈密顿量的再现标志着基于从头算的PES已成熟，现在可信赖其用于研究异构化反应。
