PHYS 471 |
| Since quantum mechanics was constructed in 1920s, solving the non-relativistic time-independent Schrödinger equation for a system of nuclei and electrons has become an essential step to understand every detail of atomic or molecular properties. In the Born-Oppenheimer approximation, nuclei effectively move on a potential energy surface obtained by solving the electronic part of the Schrödinger equation. Perhaps owing to smaller quantum effects on nuclei, most of the theoretical efforts in developing analytical approximation schemes have been put on the electronic part rather than the nuclear part. A variety of approximate methods have thus been developed in electronic structure theory. Among them, Hartree-Fock (HF) theory is known as the foundation of ab initio molecular orbital theory. Its subsequent Roothaan-Hall (RH) equations provide a practical procedure for obtaining numerical solutions for any molecular systems using HF theory. Although nuclear quantum effects are not as dominant as the electronic ones, those effects have become significant in the most advanced technology, ranging from the carbon nanotubes in materials science to the drug design in life science. To catch up with modern technology, there is a vital need for developing an ab initio theory which can systematically and practically incorporate quantum effects into nuclei with any desired accuracy. The new method proposed in this talk, which is based on Feynman-Kleinert variational perturbation theory for path integrals, hopefully can serve as the first step to develop such ab initio approach for thermodynamics and play a role similar to RH equations in electronic structure theory. The method has been tested with a wide range of fundamental systems in which exact results are available for comparisons, including Morse potential, anharmonic potential, Eckart (symmetric and asymmetric) potential, double-well potential, H + H2 collinear reaction (two-degree-of-freedom), and a water molecule (three-degree-of-freedom). Accurate results have been calculated and will be presented. |
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Physical Chemistry Poster Session
7:00 PM-9:00 PM, Wednesday, August 22, 2007 BCEC -- Exhibit Hall - B2, Poster
Sci-Mix
Division of Physical Chemistry |