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First-principles calculations of long-range intermolecular dispersion forces

<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

Identiferoai:union.ndltd.org:UPSALLA/oai:DiVA.org:liu-7512
Date January 2006
CreatorsJiemchooroj, Auayporn
PublisherLinköping University, Linköping University, Theoretical Physics, Institutionen för fysik, kemi och biologi
Source SetsDiVA Archive at Upsalla University
LanguageEnglish
Detected LanguageEnglish
TypeLicentiate thesis, comprehensive summary, text
RelationLinköping Studies in Science and Technology. Thesis, 0280-7971 ; 1217

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