Multiperturbation theory and its application to polyatomic molecules

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:7014849

Abu-Jafar, M S

A multiperturbation theory for molecular systems is proposed for the calculation of the ground state energy up to fourth-order for simple diatomic and polyatomic molecules over a wide range of internuclear separations. The hydrogenic function is chosen as the zero-order wave function rather than the Hartree-Fock function. With this choice the multiperturbation wave functions are independent of the nuclear charge and of the total number of electrons in the system, and are thus completely transferable to other systems. Results are presented of calculations on the ground state energies for the two-electron diatomic systems H[sub 2], He[sub 2][sup ++] and HeH[sup +] and two-electron polyatomic systems H[sup +][sub 3] and HeH[sub 2][sup ++]. For the homonuclear systems the energy values are very good. For the heteronuclear systems the results are better still and lead to optimism about the application of the method to larger systems. The total energies were compared with Hartree-Fock values. Results obtained for one-electron diatomic molecular ions are directly incorporated into the calculations for two-electron diatomic molecules. Results obtained for the latter are then directly incorporated into the calculations for polyatomic systems. To calculate the first- and second-order correction for the wave function of any molecule, first- and second-order corrections for one-electron diatomic molecules and some additional mixed second-order corrections are needed. These wave functions will be two-center, one-electron at most. The author extends the application of multiperturbation theory to higher order, and to the treatment of simple polyatomic molecules. The goal of this research is an efficient, inexpensive, but accurate method for computing energies of polyatomic systems, in particular potential energy surfaces useful in reactive scattering calculations.

• Research Organization: Southern Illinois Univ., Carbondale, IL (United States)
• OSTI ID: 7014849
• Country of Publication: United States
• Language: English

Related Subjects

664100* -- Theory of Electronic Structure of Atoms & Molecules-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
DATA
ELEMENTS
ENERGY LEVELS
FLUIDS
GASES
GROUND STATES
HELIUM
HELIUM COMPOUNDS
HELIUM HYDRIDES
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
INFORMATION
MOLECULES
NONMETALS
NUMERICAL DATA
PERTURBATION THEORY
RARE GAS COMPOUNDS
RARE GASES
THEORETICAL DATA