für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namen...

Ground state properties and excited states of ladder-type paraphenylene oligomers are calculated applying semiempirical methods for up to eleven phenylene rings. The results are in qualitative agreement with experimental data. A new scheme to interpret the excited states is developed which reveals the excitonic nature of the excited states. The electron-hole pair of the S1-state has a mean dist...

The rovibrational partition functions of diatomic molecules are calculated using a classical framework plus quantum, semiclassical, and semiempirical corrections. The most popular methods to calculate such corrections are briefly reviewed and applied to the benchmark H2 molecule. A novel hybrid scheme is proposed and applied to H2, HCl, and ArO. Each method is analyzed with a view to find an ec...

Several modifications that have been made to the NDDO core-core interaction term and to the method of parameter optimization are described. These changes have resulted in a more complete parameter optimization, called PM6, which has, in turn, allowed 70 elements to be parameterized. The average unsigned error (AUE) between calculated and reference heats of formation for 4,492 species was 8.0 kc...

A semiempirical AM1/d Hamiltonian is developed to model phosphoryl transfer reactions catalyzed by enzymes and ribozymes for use in linear-scaling calculations and combined quantum mechanical/molecular mechanical simulations. The model, designated AM1/d-PhoT, is parametrized for H, O, and P atoms to reproduce high-level density-functional results from a recently constructed database of quantum ...

We describe experimental and theoretical studies of the third-order nonlinear optical coefficients of methyl orange solutions under different pH conditions. A combination of semiempirical and ab initio methods was adopted to investigate the most stable geometrical structures possible for this molecule. The experimental data obtained using the Z-scan technique for the third-order nonlinear optic...

The semiempirical orthogonalization-corrected OMx methods have recently been shown to perform well in extensive ground-state benchmarks. They can also be applied to the computation of electronically excited states when combined with a suitable multireference configuration interaction (MRCI) treatment. We report on a comprehensive evaluation of the performance of the OMx/MRCI methods for electro...