<p>This work presents first-principles calculations of long-range intermolecular dispersion energies between two atoms or molecules as expressed in terms of the C<sub>6</sub> dipole-dipole dispersion coefficients. In a series of publications, it has been shown by us that the complex linear polarization propagator method provides accurate <em>ab initio</em> and first-principles density functional theory values of the C<sub>6</sub> dispersion coefficients in comparison with those reported in the literature. The selected samples for the investigation of dispersion interactions in the electronic ground state are the noble gases, <em>n</em>-alkanes, polyacenes, azabenzenes, and C<sub>60</sub>. It has been shown that the proposed method can also be used to determine dispersion energies for species in their respective excited electronic states. The C<sub>6 </sub>dispersion coefficients for the first <em>π</em> → <em>π*</em> excited state of the azabenzene molecules have been obtained with the adopted method in the multiconfiguration self-consistent field approximation. The dispersion energy of the <em>π</em> → <em>π*</em> excited state is smaller r than that of the ground state. It is found that the characteristic frequencies ω<sub>1</sub> defined in the London approximation of <em>n</em>-alkanes vary in a narrow range and that makes it possible to construct a simple structure-to-property relation based on the number of -bonds for the dispersion interaction in these saturated compounds. However, this simple approach is not applicable for the interactions of the <em>π</em>-conjugated systems since their characteristic frequencies <em>ω</em><sub>1</sub> vary strongly depending on the systems.</p> / Report code: LIU-TEK-LIC-2006:2
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:liu-7512 |
| Date | January 2006 |
| Creators | Jiemchooroj, Auayporn |
| Publisher | Linköping University, Linköping University, Theoretical Physics, Institutionen för fysik, kemi och biologi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Licentiate thesis, comprehensive summary, text |
| Relation | Linköping Studies in Science and Technology. Thesis, 0280-7971 ; 1217 |
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