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Quantum Mechanical Investigation of Polymeric Properties Using a Combination of First Principle Quantum Chemical and Solid State Physical Methods.

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Final rept. 1 Jul 96-30 Jun 97,

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The Hartree-Fock HF crystal orbital code as well as its correction for correlation has been rewritten in FORTRAN 90 in a vectorized form. This language has several advantages. We have performed also a multipole expansion for the not explicitly calculated Coulomb integrals and introduced different tresholds for different types of integrals. The new program packages will be completely ready and tested in about two months. A copy of them will be sent to the Air Force Office of Scientific Research as well as to Dr. Doug Dudis at Wright-Patterson Air Force Base. Using our present HF and QP band structure programs we have calculated polyparaphenylene-vinylidene and the four nucleotide base stacks. We have started to compute also different homopolypeptides. The results in the first case show that to obtain a good agreement between the calculated gap 4.87 eV and the one estimated from experimental data, one has to perform a 2D calculation. In the case of the cytosine C stack we have improved our double basis by inserting at the half stacking distance a virtual C molecule. The calculated gap value of 6.60 eV is close to the value estimated from the exciton spectra of C 5.5 eV. On the basis of this also the gaps of the other base stacks could be improved. Finally we have already calculated the QP band structures of polyserine and polythreonine. The obtained gap values are by about 4 eV smaller than the corresponding HF ones.

Subject Categories:

  • Physical Chemistry
  • Numerical Mathematics
  • Computer Programming and Software

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