Poveda L A, Biczysko M, Varandas A J C
Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal.
J Chem Phys. 2009 Jul 28;131(4):044309. doi: 10.1063/1.3176512.
A global single-sheeted double many-body expansion potential energy surface is reported for the ground electronic state of N(2)H(2). Starting from an approximate cluster expansion of the molecular potential that utilizes previously reported functions of the same family for the triatomic fragments, four-body energy terms have been calibrated from extensive accurate ab initio data so as to reproduce the main features of the title system. The switching function formalism previously suggested for three-body systems [A. J. C. Varandas and L. Poveda, Theor. Chem. Acc. 116, 404 (2006)] has been generalized to approximate the true multisheeted nature of N(2)H(2) potential energy surface, thus allowing the correct behavior at the N((2)D) + NH(2)((2)A(")) and N((4)S) + NH(2)((4)A(")) dissociation limits. The resulting fully six-dimensional potential energy function reproduces the correct symmetry under permutation of identical atoms and predicts the main stationary points of the molecule in the valence and long-range regions in good agreement with available experimental and theoretical data on the diazene molecule.
报道了N₂H₂基态电子态的一个全局单叶双多体展开势能面。从分子势能的近似团簇展开出发，利用先前报道的同一族函数描述三原子片段，根据大量精确的从头算数据校准了四体能量项，以再现标题体系的主要特征。先前为三体系统提出的开关函数形式（A. J. C. 瓦兰达斯和L. 波韦达，《理论化学学报》116, 404 (2006)）已被推广，以近似N₂H₂势能面的真实多叶性质，从而在N((²D)) + NH₂((²A″))和N((⁴S)) + NH₂((⁴A″))解离极限处给出正确行为。所得的全六维势能函数在相同原子置换下再现了正确的对称性，并预测了分子在价态和长程区域的主要驻点，与重氮烯分子现有的实验和理论数据高度吻合。
