College of Chemistry, Beijing Normal University, Beijing, 100875, China.
J Phys Chem A. 2009 Dec 3;113(48):13608-20. doi: 10.1021/jp905928u.
Theoretical investigations of the equilibrium structures and associated isomerization reactions of the hydrogen clusters H(6)(+) have been carried out. Three equilibrium structures and three isomerization transition states were located on the electronic doublet and quartet states of the respective potential energy surfaces. The research employed ab initio self-consistent-field (SCF), coupled cluster (CC) with single and double excitations (CCSD), CCSD with perturbative triple excitations (CCSD(T)), and full triple excitations (CCSDT) wave functions and a wide variety of correlation-consistent polarized valence cc-pVXZ and aug-cc-pVXZ (where X = D, T, Q) basis sets. For each structure the geometry, energy, dipole moment, harmonic vibrational frequencies, and infrared intensities are predicted. Complete active space SCF (CASSCF) and multireference configuration interaction (MRCI) wave functions are used to analyze the effect of correlation on physical properties and energetics. Extensive focal point analyses (including CCSDTQ and full CI energies and basis sets up to sextuple zeta) are used to obtain complete basis set (CBS) limit energies. The H(2)(+)-core H(6)(+) cluster with D(2d) symmetry is the global minimum, lying 3.9 (4.2) +/- 0.1 kcal mol(-1) below the H(3)(+)-core H(6)(+) cluster with C(s) symmetry, where zero-point vibrational energy (ZPVE) corrected value are shown in parentheses. The barrier of the isomerization reaction between these two structures is 7.4 (5.2) +/- 0.1 kcal mol(-1). The dissociation energies for the H(2)(+)-core H(6)(+) isomer [H(6)(+) (D(2d)) --> 2H(2) + H(2)(+)] and the H(3)(+)-core H(6)(+) isomer [H(6)(+) (C(s)) --> H(3)(+) + H(2) + H] are 57.5 (50.9) +/- 0.1 and 12.3 (8.3) +/- 0.1 kcal mol(-1), respectively.
已对氢团簇 H(6)(+)的平衡结构和相关异构化反应进行了理论研究。在电子双重态和四重态的相应势能面上，确定了三种平衡结构和三种异构化过渡态。研究采用了从头算自洽场 (SCF)、单和双激发耦合簇 (CC) (CCSD)、微扰三激发耦合簇 (CCSD(T)) 和全三激发耦合簇 (CCSDT) 波函数以及各种相关一致极化价 cc-pVXZ 和 aug-cc-pVXZ（其中 X = D、T、Q）基组。对于每个结构，预测了几何形状、能量、偶极矩、简谐振动频率和红外强度。完全活性空间自洽场 (CASSCF) 和多参考组态相互作用 (MRCI) 波函数用于分析相关对物理性质和能态的影响。广泛的焦点分析（包括 CCSDTQ 和全 CI 能量以及直到六重 zeta 的基组）用于获得完全基组 (CBS) 极限能量。具有 D(2d)对称性的 H(2)(+)-核 H(6)(+)团簇是全局最小值，比具有 C(s)对称性的 H(3)(+)-核 H(6)(+)团簇低 3.9（4.2）±0.1 kcal mol(-1)，括号内显示零振动能（ZPVE）校正值。这两种结构之间异构化反应的势垒为 7.4（5.2）±0.1 kcal mol(-1)。H(2)(+)-核 H(6)(+)异构体[H(6)(+) (D(2d)) --> 2H(2) + H(2)(+)]和 H(3)(+)-核 H(6)(+)异构体[H(6)(+) (C(s)) --> H(3)(+) + H(2) + H]的离解能分别为 57.5（50.9）±0.1 和 12.3（8.3）±0.1 kcal mol(-1)。
