Huang Xinchuan, Braams Bastiaan J, Bowman Joel M
Cherry L. Emerson Center of Scientific Computation, Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
J Phys Chem A. 2006 Jan 19;110(2):445-51. doi: 10.1021/jp053583d.
A full-dimensional ab initio potential energy surface (PES) and dipole moment surface (DMS) are reported for the water dimer, (H2O)2. The CCSD(T)-PES is a very precise fit to 19,805 ab initio energies obtained with the coupled-cluster (CCSD(T)) method, using an aug-cc-pVTZ basis. The standard counterpoise correction was applied to approximately eliminate basis set superposition errors. The fit is based on an approach that incorporates the permutational symmetry of identical atoms [Huang, X.; Braams, B.; Bowman, J. M. J. Chem.Phys. 2005, 122, 044308]. The DMS is a fit to the dipole moment obtained with Møller-Plesset (MP2) theory, using an aug-cc-pVTZ basis. The PES has an RMS fitting error of 31 cm(-1) for energies below 20,000 cm(-1), relative to the global minimum. This surface can describe various internal floppy motions, including various monomer inversions, and isomerization pathways. Ten characteristic stationary points have been located on the surface, four of which are transition structures and the rest are higher order saddle points. Their geometrical and vibrational properties are presented and compared with available previous theoretical work. The CCSD(T)-PES and MP2-DMS dissociate correctly (and symmetrically) to two H2O monomers, with D(e) = 1665.7 cm(-1) (19.93 kJ/mol). Accurate quantum calculations of the zero-point energy of the dimer (using diffusion Monte Carlo) and the monomers (using a vibrational configuration interaction approach) are reported, and these together with D(e) give a value of D0 of 1042 cm(-1) (12.44 kJ/mol). A best estimated value is 1130 cm(-1) (13.5 kJ/mol).
报道了水二聚体（H₂O）₂的全维从头算势能面（PES）和偶极矩面（DMS）。CCSD（T）-PES是使用aug-cc-pVTZ基组，通过耦合簇（CCSD（T））方法对19805个从头算能量进行的非常精确的拟合。应用了标准的抵消校正以近似消除基组叠加误差。该拟合基于一种纳入相同原子置换对称性的方法[黄，X.；布拉姆斯，B.；鲍曼，J.M.《化学物理杂志》2005年，122，044308]。DMS是使用aug-cc-pVTZ基组，对用莫勒-普列斯特定理（MP2）得到的偶极矩进行的拟合。相对于全局最小值，对于低于20000 cm⁻¹的能量，PES的均方根拟合误差为31 cm⁻¹。该表面可以描述各种内部松弛运动，包括各种单体反转和异构化途径。在该表面上已定位了十个特征驻点，其中四个是过渡结构，其余是高阶鞍点。给出了它们的几何和振动性质，并与先前可用的理论工作进行了比较。CCSD（T）-PES和MP2-DMS正确（且对称地）解离为两个H₂O单体，解离能D（e） = 1665.7 cm⁻¹（19.93 kJ/mol）。报道了二聚体零点能（使用扩散蒙特卡罗方法）和单体零点能（使用振动组态相互作用方法）的精确量子计算，这些与D（e）一起给出D₀的值为1042 cm⁻¹（12.44 kJ/mol）。最佳估计值为1130 cm⁻¹（13.5 kJ/mol）。
