# Research

**
Research projects completed **

1. In the course of this project, I developed a program package for computations using the so-called Mutually Consistent Field (MCF) theory which deals with the ab initio calculation of interactions between an arbitrary number of molecules. The method was numerically applied to the problem of a glycine ion in aqueous solution. The results agreed satisfactorily with corresponding data from more exact calculations. Further I developed an approximate method to apply this method also to polymers, by cutting them into subunits with the help of localized orbitals.

2. As described in more detail in my Ph.D. thesis, a method was developed and applied which allows to compute the correlation energy of large molecules with the help of the Coupled Cluster method together with the use of localized orbitals. Calculations on several test systems and on the nucleotide bases of DNA were performed.

3. A Hartree Fock crystal orbital program was developed in the course of my Ph.D work which for the first time could also be applied to infinite polymers exhibiting helical symmetry. In this project we considered for the first time to act with the rotation operator on Hartree Fock density matrices during the iterations, instead of performing the symmetry operation on the very large number of two-electron integrals. Calculations on polyethylene and teflon were performed.

4. In cooperation with Professor Dr. G. Del Re from Rome we performed time dependent calculations on vibrating model systems using a discrete state approach. In the course of this project we also developed the formalism further.

**
Research projects in progress**

1. Dynamics of non-linear quasiparticles, especially solitons in trans-polyacetylene and pernigraniline, Davydov solitons in proteins, conformational solitons in the base stacks of DNA, and polarons in cis-polyacetylene, polyparaphenylene, polyfurane, -pyrrole, and -thiophene with emphasis of quantum-, temperature- and disorder-effects on their dynamics. Application of semiempirical π-electron theories together with adiabatic and quantum dynamics to two dimensional systems and fullerenes. This project is funded by a new grant of the "Deutsche Forschungsgemeinschaft", and was partially funded by the same organization under another grant for 5 years. The project is aimed to lead to a concept for the theoretical design of conducting polymers (synthetic metals, theoretical materials research). Consideration of semiempirical all valence electron theories and density functional methods to replace the π-electron models (funding of this project is granted by the "Deutsche Forschungsgemeinschaft", however, the grant had to be closed because of my shift to Arabia, where I will renew it). A proposal for funding by KFUPM is under consideration.

2. Comparative
application of the Dynamical Self Trapping (DST) equations and of
discrete state methods to the localization of molecular vibrations,
e.g. in first row hydrides (BeH_{2}, BH_{3}, B_{2}H_{6},
CH_{4}, NH_{3}, H_{2}O) and mono-deuterated
benzene. Calculation of (anharmonic) potential surfaces on
correlated ab initio level for these vibrations.

3. We want to use energy dependent exchange-correlation functionals, especially the self-energy-corrected (SIC) functional in density functional theory (DFT) to be able to improve the performance of DFT in the calculation of excited states. Here we want to develop program packages for ab initio applications to molecules and one-dimensional infinite polymers. In case that the SIC functional does not work satisfactorily we also want to test the idea (published previously by others) to apply quasiparticle concepts together with Green function methods to the problem (funding of this project is granted by the "Deutsche Forschungsgemeinschaft", however, the grant had to be closed because of my shift to Arabia, where I submitted a proposal for this project).

4. Application of the ab initio Coupled Cluster Theory for the calculation of correlation energies and correlation corrections to the band structure of polymers with the help of localized Wannier-Boys functions. This project was funded for 5 years by the "Deutsche Forschungsgemeinschaft" and is now completed. Afterwards a couple of applications to several polymers is planned.

5. Together with Professor Dr. J. Ladik we are working, as described in more detail in my habilitation thesis, on long range mechanisms for the understanding of the action of chemical carcinogens as well as of radiation (leading to double strand breaking) on DNA. A review of experimental observations and theories including ours was published as a Springer book by Prof. Ladik and myself this September.

6. In the framework of a smaller project we are trying, in cooperation with Professor Ladik and the Theoretical Particle Physics group, Professor Reinhard, in Erlangen, to apply Gaussian basis sets together with quantum chemical methods to a soliton model commonly used in theoretical elementary particle physics (Soliton Bag Model) to compute the structure of nuclear matter on the basis of quantum chromodynamics for the interactions between quarks.

7. In order to reach a qualitative understanding of the Surface Enhanced Raman Effect (SERE) we calculate the Raman spectra of pyridine and clusters composed of pyridine and silver atoms. For the purpose of the embedding of such clusters into a silver surface we have developed a methodology so far, which is still in the stage of programming. This project is performed in close collaboration with the group of Prof. S. Schneider from the Department of Physical Chemistry at the University Erlangen-Nürnberg.

8. Calculation of infrared and Raman spectra for small molecules. The project is funded by KFUPM.