Huang Xinchuan, Braams Bastiaan J, Bowman Joel M
Cherry L. Emerson Center of Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30322, USA.
J Chem Phys. 2005 Jan 22;122(4):44308. doi: 10.1063/1.1834500.
Full-dimensional ab initio potential energy surface (PES) and dipole moment surface (DMS) are reported for H(5)O(2) (+). Tens of thousands of coupled-cluster [CCSD(T)] and second-order Moller-Plesset (MP2) calculations of electronic energies, using aug-cc-pVTZ basis, were done. The energies were fit very precisely in terms of all the internuclear distances, using standard least-square procedures, however, with a fitting basis that satisfies permutational symmetry with respect to like atoms. The H(5)O(2) (+) PES is a fit to 48 189 CCSD(T) energies, containing 7962 polynomial coefficients. The PES has a rms fitting error of 34.9 cm(-1) for the entire data set up to 110 000 cm(-1). This surface can describe various internal floppy motions, including the H atom exchanges, monomer inversions, and monomer torsions. First- and higher-order saddle points have been located on the surface and compared with available previous theoretical work. In addition, the PES dissociates correctly (and symmetrically) to H(2)O+H(3)O(+), with D(e)=11 923.8 cm(-1). Geometrical and vibrational properties of the monomer fragments are presented. The corresponding global DMS fit (MP2 based) involves 3844 polynomial coefficients and also dissociates correctly.
报道了H(5)O(2) (+)的全维从头算势能面（PES）和偶极矩面（DMS）。使用aug-cc-pVTZ基组进行了数万次耦合簇[CCSD(T)]和二阶莫勒-普列斯特定理（MP2）电子能量计算。利用标准最小二乘法，根据所有核间距对能量进行了非常精确的拟合，不过，拟合基组满足同类原子的置换对称性。H(5)O(2) (+)的PES拟合了48189个CCSD(T)能量，包含7962个多项式系数。对于高达110000 cm(-1)的整个数据集，PES的均方根拟合误差为34.9 cm(-1)。该表面可以描述各种内部松弛运动，包括H原子交换、单体反转和单体扭转。已在该表面上找到一阶和高阶鞍点，并与之前可用的理论工作进行了比较。此外，PES正确（且对称地）解离为H(2)O + H(3)O(+)，解离能D(e)=11923.8 cm(-1)。给出了单体片段的几何和振动性质。相应的全局DMS拟合（基于MP2）涉及3844个多项式系数，且也能正确解离。
