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Your search keyword '"Niehaus, T.A."' showing total 8 results
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8 results on '"Niehaus, T.A."'

4. A global investigation of excited state surfaces within time-dependent density-functional response theory.

Author

Wanko, M., Garavelli, M., Bernardi, F., Niehaus, T.A., Frauenheim, T., and Elstner, M.

Subjects
DENSITY functionals, EXCITED state chemistry, POTENTIAL energy surfaces, MOLECULES, POLYENES, PHYSICAL & theoretical chemistry
Abstract

This work investigates the capability of time-dependent density functional response theory to describe excited state potential energy surfaces of conjugated organic molecules. Applications to linear polyenes, aromatic systems, and the protonated Schiff base of retinal demonstrate the scope of currently used exchange-correlation functionals as local, adiabatic approximations to time-dependent Kohn–Sham theory. The results are compared to experimental and ab initio data of various kinds to attain a critical analysis of common problems concerning charge transfer and long range (nondynamic) correlation effects. This analysis goes beyond a local investigation of electronic properties and incorporates a global view of the excited state potential energy surfaces. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2004
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6. Vibrational absorption spectra, DFT and SCC-DFTB conformational study and analysis of [Leu]enkephalin

Author

Abdali, Salim, Niehaus, T.A., Jalkanen, Karl J., Cao, X., Nafie, L.A., Frauenheim, T., Suhai, S., Bohr, Henrik, Abdali, Salim, Niehaus, T.A., Jalkanen, Karl J., Cao, X., Nafie, L.A., Frauenheim, T., Suhai, S., and Bohr, Henrik

Abstract

The endogenous morphine-like pentapeptide, [Leu]enkephalin, which binds to the opiate receptor in the brain, spinal core and gut, is the subject of this study. Vibrational absorption (VA) measurements were carried out on [Leu] enkephalin in non-polar solvent, DMSO-D6 to stabilize the environment. Ab initio (DFT at the B3LYP/6-31G* level of theory) and semi-empirical (SCC-DFTB) with and without dispersion correction were applied to simulate the VA spectra of [Leu] enkephalin. In these calculations structures taken from X-ray measurements for different conformers of the molecule were used as initial structures for SCC-DFTB geometry optimizations, while the optimized SCC-DFTB geometries were used as initial structures for the DFT geometry optimizations. The experimental VA spectrum and the VA spectra calculated for the low energy conformers at each level of theory are then compared for different conformers of this peptide. This comparison allowed structural study of this molecule as it is here presented.

Published
2003

8. Excited State Properties of Allylamine-Capped Silicon Quantum Dots

Author

Wang, X., Zhang, R.Q., Niehaus, T.A., and Frauenheim, Th.

Abstract

Excited-state properties of allylamine-capped silicon quantum dots (SiQDs) from Si10to Si59are studied using a density-functional tight-binding method and compared with available experimental data. Signatures in vibrational and optical absorption spectra are revealed, which show the detailed effect of modification of the SiQDs with allylamine. It is verified that the modification could be expected to not only reduce the surface oxidation rate but also maintain an efficient electronic transition feature that facilitates blue emission. The optical properties show significant size dependence due to the quantum confinement effect. The increase in the number of allylamine molecules could only result in a slight red shift of emission spectra.

Published
2007
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