Ab initio and Gordon--Kim intermolecular potentials for two nitrogen molecules

Journal Article · Tue Jul 01 04:00:00 EDT 1980 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.439878· OSTI ID:5294944

Ree, F H; Winter, N W

Both ab initio MO--LCAO--SCF and the electron-gas (or Gordon--Kim) methods have been used to compute the intermolecular potential (Phi) of N/sub 2/ molecules for seven different N/sub 2/--N/sub 2/ orientations. The ab initio calculations were carried out using a (4s3p) contracted Gaussian basis set with and without 3d polarization functions. The larger basis set provides adequate results for Phi>0.002 hartree or intermolecular separations less than 6.5--7 bohr. We use a convenient analytic expression to represent the ab initio data in terms of the intermolecular distance and three angles defining the orientations of the two N/sub 2/ molecules. The Gordon--Kim method with Rae's self-exchange correction yields Phi, which agrees reasonably well over a large repulsive range. However, a detailed comparison of the electron kinetic energy contributions shows a large difference between the ab initio and the Gordon--Kim calculations. Using the ab initio data we derive an atom--atom potential of the two N/sub 2/ molecules. Although this expression does not accurately fit the data at some orientations, its spherical average agrees with the corresponding average of the ab initio Phi remarkably well. The spherically averaged ab initio Phi is also compared with the corresponding quantities derived from experimental considerations. The approach of the ab initio Phi to the classical quadrupole--quadrupole interaction at large intermolecular separation is also discussed.

• Research Organization: University of California, Lawrence Livermore Laboratory, Livermore, California 94550
• OSTI ID: 5294944
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 73:1; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

640300* -- Atomic
Molecular & Chemical Physics
74 ATOMIC AND MOLECULAR PHYSICS
CRYOGENIC FLUIDS
ELEMENTS
ENERGY
FLUIDS
FUNCTIONS
INTERMOLECULAR FORCES
NITROGEN
NONMETALS
POTENTIAL ENERGY
SELF-CONSISTENT FIELD
WAVE FUNCTIONS