UBC Theses and Dissertations
Study of the BH molecule Gagnon, Paul Joseph
Antisymmetrized geminal product wavefunctions with several limited basis sets were calculated for the ground state of BH at R=2.329 atomic units. Extending these wavefunctions to include Kapuy's "one-electron transfer" configurations resulted in a lowering in energy of ~0.01 atomic units. In our case, this improvement accounts for more than 90% of that achieved by a full configuration-interaction wavefunction. A "contracted" double-zeta basis set yielded the best overall energy. A 13-term, "split core", configuration-interaction wavefunction was developed and yielded an energy of -25.14769 atomic units. This wavefunction was then made to satisfy the virial theorem. Parr and White's method for one-point force constant calculation was applied to the scaled wavefunction with negative results. A similar wavefunction was partially optimized at three internuclear distances followed by scaling with fixed R.Various parabolic models were used to fit the virial forces and energies corresponding to each R value. The force constants k(e) calculated from these models were usually very good and the effect of scaling was shown to be important. Parabolic expansions in 1/R gave better results than parabolas in R, compared to a quintic model and to experimental values.
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