Variační a poruchové výpočty interakčních energií nekovalentních klastrů

Hostaš, Jiří

Calculation of noncovalent interactions in set of complexes containing halogen atom (called Halogensx10) is the main subject of this thesis. Wide variety of semiempirical quantum mechanical (SQM) methods (AM1, RM1, PM3, PM6 and SCC-DFTB augmented with empirical correction for dispersion interaction and hydrogen bonding (D3H4)) have been tested and their accuracy was discussed. The SCC-DFTB-D3H4 method showed the advantage of no artificial behaviour for other types of interactions with exception of halogen bonding which is underestimated. Specific correction for halogen bonding was designed as a purely empirical fix of serious underestimation of interaction energy in halogen bonded complexes that yields results for validation set very close to benchmark interaction energies with average error is 0.3 kcal/mol ~ 6% of the interaction energy. As a benchmark method the CCSD(T) extrapolated to the CBS limit, according to Helgaker's scheme with rather large correlation consistent basis sets has been used. The results presented herein can be used in the rational design of halogenated ligands as well as in research of another halogen enriched compounds.

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