Viel Alexandra, Coutinho-Neto Maurício D, Manthe Uwe
Theoretische Chemie, TU München, Lichtenbergstrasse 4, D-85747 Garching, Germany.
J Chem Phys. 2007 Jan 14;126(2):024308. doi: 10.1063/1.2406074.
Quantum dynamics calculations of the ground state tunneling splitting and of the zero point energy of malonaldehyde on the full dimensional potential energy surface proposed by Yagi et al. [J. Chem. Phys. 1154, 10647 (2001)] are reported. The exact diffusion Monte Carlo and the projection operator imaginary time spectral evolution methods are used to compute accurate benchmark results for this 21-dimensional ab initio potential energy surface. A tunneling splitting of 25.7+/-0.3 cm-1 is obtained, and the vibrational ground state energy is found to be 15 122+/-4 cm-1. Isotopic substitution of the tunneling hydrogen modifies the tunneling splitting down to 3.21+/-0.09 cm-1 and the vibrational ground state energy to 14 385+/-2 cm-1. The computed tunneling splittings are slightly higher than the experimental values as expected from the potential energy surface which slightly underestimates the barrier height, and they are slightly lower than the results from the instanton theory obtained using the same potential energy surface.
报道了基于八木等人[《化学物理杂志》1154, 10647 (2001)]提出的全维势能面，对丙二醛基态隧穿分裂和零点能的量子动力学计算。采用精确的扩散蒙特卡罗方法和投影算符虚时间谱演化方法，为这个21维的从头算势能面计算出精确的基准结果。得到的隧穿分裂为25.7±0.3 cm-1，振动基态能量为15122±4 cm-1。隧穿氢的同位素取代使隧穿分裂降低至3.21±0.09 cm-1，振动基态能量降低至14385±2 cm-1。计算得到的隧穿分裂比实验值略高，这正如从略微低估势垒高度的势能面所预期的那样，并且它们比使用相同势能面得到的瞬子理论结果略低。
