Citation
Kahn, Luis R. (1972) I. Abinitio effective potentials for use in molecular calculations. II. The Sternheimer correction, perturbation theory, and approximate wavefunctions. III. The theoretical determination of the Li_2 B^1π_u potential energy curve. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:11202009150548056
Abstract
Part I: We have investigated the efficacy of abinitio effective potentials in replacing the core electrons of atoms for use in molecular calculations. The effective potentials are obtained from ab initio GI calculations on atoms and are unique and local. We find that the use of these effective potentials to replace the core orbitals of such molecules as LiH, Li_2, BH, or LiH_2, leads to wavefunctions in excellent agreement with allelectron abinitio results. The use of such effective potentials should allow abinitio quality wavefunctions to be obtained for systems too large for the abinitio consideration of all the electrons. Part II: We have investigated the Sternheimer correction for the calculation of the nuclear quadrupole coupling constants and its relation to the approximate nature of the zeroorder wave function. The firstorder perturbed HartreeFock equations, and some approximations to them, are solved for the 2^2P state of Li, and the resulting Sternheimer type corrections are compared with Sternheimeris approximate calculations and with results from nonperturbation theory approaches. PART III: The Li_2 B^1π_u potential energy curve has been calculated with a MultiConfiguration SCF (MCSCF) wavefunction. Several different types of wavefunctions and basis sets have been examined and their accuracy determined. The most accurate wavefunction used predicts a binding energy of 0.3015 e.V. (84% of the experimental value of 0.362 e.V.), and predicts a potential hump of 0.0724 e.V. with its maximum in the vicinity of 10.6 Bohr. It is argued that the theoretical value of the hump is an upper bound to the experimental value.
Item Type:  Thesis (Dissertation (Ph.D.)) 

Subject Keywords:  Chemistry 
Degree Grantor:  California Institute of Technology 
Division:  Chemistry and Chemical Engineering 
Major Option:  Chemistry 
Thesis Availability:  Public (worldwide access) 
Research Advisor(s): 

Thesis Committee: 

Defense Date:  30 September 1971 
Record Number:  CaltechTHESIS:11202009150548056 
Persistent URL:  http://resolver.caltech.edu/CaltechTHESIS:11202009150548056 
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  5394 
Collection:  CaltechTHESIS 
Deposited By:  Tony Diaz 
Deposited On:  01 Dec 2009 19:03 
Last Modified:  26 Dec 2012 03:19 
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