Moss, Barry Joel (1975) I. The generalized valence bond description of O_2 II. Configuration interaction studies on low-lying states of O_2. Master's thesis, California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:03312010-111428333
I. The Generalized Valence Bond Description of O_2 Ab initio calculations using the generalized valence bond (GVB) method have been carried out for the lowest triplet and singlet states of O_2 at internuclear distances (R) between 2a_o and 6a_o. In contrast to other orbital descriptions, GVB leads correctly to ground state oxygen atoms as the bond length is increased to infinity. This proper behavior requires optimization of the spatial orbitals themselves and of the permutational coupling between them as well. Analysis of the results as a function of R is straightforward. Constructing a simple configuration interaction (CI) wavefunction using the GVB orbitals leads to excellent potential curves, accounting for 94% of the bond dissociation energy. The calculated adiabatic separation of the singlet and triplet states is 1.09 eV compared with the experimental T_e of 1.01 eV. II. Configuration Interaction Studies on Low-Lying States of O_2 Configuration interaction calculations are reported as a function of R for the nine state of O_2 corresponding to the (3σ_g)^2 (1π_μ)^4 (1π_g)^2 and (3σ_g)^2 (1π_μ)^3 (1π_g)^3 configurations (X^3∑^-_g, a^1Δ_g, b^1∑^+_g, ^1∑^-_μ, ^3Δ_μ, A^3∑^+_μ, B^3∑^-_μ, ^1Δ_μ, ^1∑^+_μ). By using the generalized valence bond (GVB) orbitals of the X^3∑^-_g state we obtain good quality GVB-CI wavefunctions with only a moderate number of configurations(72 to 98 spatial configurations) despite the use of a large basis set (double-zeta plus polarization functions). The calculated D_e for the X^3∑^-_μ state is 4.88 eV, 93% of the experimental value. The calculated adiabatic excitation energies are on the average about 0.1 eV from the experimental values.
|Item Type:||Thesis (Master's thesis)|
|Degree Grantor:||California Institute of Technology|
|Division:||Chemistry and Chemical Engineering|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||10 January 1975|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||16 Apr 2010 17:12|
|Last Modified:||26 Dec 2012 03:23|
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