Ab initio potential energy surfaces for NH((3)Sigma(-))-NH((3)Sigma(-)) with analytical long range

作者：Janssen Lie**eth M C^*; Groenenboom Gerrit C; van der Avoird Ad; Zuchowski Piotr S; Podeszwa Rafal

来源：Journal of Chemical Physics, 2009, 131(22): 224314.

DOI：10.1063/1.3268920

• ab initio calculations
• coupled cluster calculations
• nitrogen compounds
• perturbation theory
• potential energy surfaces
• triplet state

We present four-dimensional ab initio potential energy surfaces for the three different spin states of the NH((3)Sigma(-))-NH((3)Sigma(-)) complex. The potentials are partially based on the work of Dhont [J. Chem. Phys. 123, 184302 (2005)]. The surface for the quintet state is obtained at the RCCSD(T)/augmented correlation-consistent polarized valence triple-zeta (aug-cc-pVTZ) level of theory and the energy differences with the singlet and triplet states are calculated at the complete active space with nth-order perturbation theory/aug-cc-pVTZ (n=2,3) level of theory. The ab initio potentials are fitted to coupled spherical harmonics in the angular coordinates, and the long range is further expanded as a power series in 1/R. The RCCSD(T) potential is corrected for a size-consistency error of about 0.5x10(-6) E-h prior to fitting. The long-range coefficients obtained from the fit are found to be in good agreement with first and second-order perturbation theory calculations.

• 出版日期2009-12-14