@article{13520, abstract = {{Atomistic simulations in the framework of the density functional theory have been used to model morphologic and vibrational properties of lithium niobate–lithium tantalate mixed crystals as a function of the [Nb]/[Ta] ratio. Structural parameters such as the crystal volume and the lattice parameters a and c vary roughly linearly from LiTaO3 to LiNbO3, showing only minor deviations from the Vegard behavior. Our ab initio calculations demonstrate that the TO1, TO2 and TO4 vibrational modes become harder with increasing Nb concentration. TO3 becomes softer with increasing Nb content, instead. Furthermore, the investigated zone center A1 -TO phonon modes are characterized by a pronounced stoichiometry dependence. Frequency shifts as large as 30 cm−1 are expected as the [Nb]/[Ta] ratio grows from 0 to 1. Therefore, spectroscopic techniques sensitive to the A1 modes (such as Raman spectroscopy), can be employed for a direct and non-destructive determination of the crystal composition.}}, author = {{Sanna, Simone and Riefer, A. and Neufeld, Sergej and Schmidt, Wolf Gero and Berth, Gerhard and Rüsing, Michael and Widhalm, A. and Zrenner, Artur}}, issn = {{0015-0193}}, journal = {{Ferroelectrics}}, keywords = {{Ferroelectrics, vibrational properties, LiNbO3, LiTaO3, mixed crystals}}, number = {{1}}, pages = {{63--68}}, title = {{{Vibrational Fingerprints of LiNbO3-LiTaO3Mixed Crystals}}}, doi = {{10.1080/00150193.2013.821893}}, volume = {{447}}, year = {{2013}}, } @article{13517, author = {{Jesser, Anton and Rohrmüller, Martin and Schmidt, Wolf Gero and Herres-Pawlis, Sonja}}, issn = {{0192-8651}}, journal = {{Journal of Computational Chemistry}}, number = {{1-2}}, pages = {{1--17}}, title = {{{Geometrical and optical benchmarking of copper guanidine-quinoline complexes: Insights from TD-DFT and many-body perturbation theory†}}}, doi = {{10.1002/jcc.23449}}, volume = {{35}}, year = {{2013}}, } @article{13521, author = {{Sanna, S. and Rode, S. and Hölscher, R. and Klassen, S. and Marutschke, C. and Kobayashi, K. and Yamada, H. and Schmidt, Wolf Gero and Kühnle, A.}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, title = {{{Charge compensation by long-period reconstruction in strongly polar lithium niobate surfaces}}}, doi = {{10.1103/physrevb.88.115422}}, volume = {{88}}, year = {{2013}}, } @article{13522, author = {{Aldahhak, Hazem and Schmidt, Wolf Gero and Rauls, E.}}, issn = {{0039-6028}}, journal = {{Surface Science}}, pages = {{242--248}}, title = {{{Adsorption of PTCDA on NaCl(100) and KCl(100)}}}, doi = {{10.1016/j.susc.2013.08.003}}, volume = {{617}}, year = {{2013}}, } @article{13519, author = {{Riefer, A. and Sanna, S. and Schmidt, Wolf Gero}}, issn = {{0015-0193}}, journal = {{Ferroelectrics}}, pages = {{78--85}}, title = {{{LiNb1-xTaxO3Electronic Structure and Optical Response fromFirst-PrinciplesCalculations}}}, doi = {{10.1080/00150193.2013.821904}}, volume = {{447}}, year = {{2013}}, } @article{13528, author = {{George, B. M. and Behrends, J. and Schnegg, A. and Schulze, T. F. and Fehr, M. and Korte, L. and Rech, B. and Lips, K. and Rohrmüller, M. and Rauls, E. and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, number = {{13}}, title = {{{Atomic Structure of Interface States in Silicon Heterojunction Solar Cells}}}, doi = {{10.1103/physrevlett.110.136803}}, volume = {{110}}, year = {{2013}}, } @article{13527, author = {{Rohrmüller, M. and Herres-Pawlis, S. and Witte, M. and Schmidt, Wolf Gero}}, issn = {{0192-8651}}, journal = {{Journal of Computational Chemistry}}, pages = {{1035--1045}}, title = {{{Bis-μ-oxo and μ-η2:η2-peroxo dicopper complexes studied within (time-dependent) density-functional and many-body perturbation theory}}}, doi = {{10.1002/jcc.23230}}, volume = {{34}}, year = {{2013}}, } @article{13525, abstract = {{The frequency-dependent dielectric function and the second-order polarizability tensor of ferroelectric LiNbO3 are calculated from first principles. The calculations are based on the electronic structure obtained from density-functional theory. The subsequent application of the GW approximation to account for quasiparticle effects and the solution of the Bethe-Salpeter equation for the stoichiometric material yield a dielectric function that slightly overestimates the absorption onset and the oscillator strength in comparison with experimental measurements. Calculations at the level of the independent-particle approximation indicate that these deficiencies are, at least, partially related to the neglect of intrinsic defects typical for the congruent material. The second-order polarizability calculated within the independent-particle approximation predicts strong nonlinear coefficients for photon energies above 1.5 eV. The comparison with measured data suggests that the inclusion of self-energy effects in the nonlinear optical response leads to a better agreement with experiments. The intrinsic defects of congruent samples reduce the optical nonlinearities, in particular, for the 21 and 31 tensor components, further improving the agreement between experiments and theory.}}, author = {{Riefer, Arthur and Sanna, Simone and Schindlmayr, Arno and Schmidt, Wolf Gero}}, issn = {{1550-235X}}, journal = {{Physical Review B}}, number = {{19}}, publisher = {{American Physical Society}}, title = {{{Optical response of stoichiometric and congruent lithium niobate from first-principles calculations}}}, doi = {{10.1103/PhysRevB.87.195208}}, volume = {{87}}, year = {{2013}}, } @article{15867, author = {{Tautz, Raphael and Da Como, Enrico and Wiebeler, Christian and Soavi, Giancarlo and Dumsch, Ines and Fröhlich, Nils and Grancini, Giulia and Allard, Sybille and Scherf, Ullrich and Cerullo, Giulio and Schumacher, Stefan and Feldmann, Jochen}}, issn = {{0002-7863}}, journal = {{Journal of the American Chemical Society}}, pages = {{4282--4290}}, title = {{{Charge Photogeneration in Donor–Acceptor Conjugated Materials: Influence of Excess Excitation Energy and Chain Length}}}, doi = {{10.1021/ja309252a}}, year = {{2013}}, } @article{15866, author = {{Ardizzone, Vincenzo and Lewandowski, Przemyslaw and Luk, M. H. and Tse, Y. C. and Kwong, N. H. and Lücke, Andreas and Abbarchi, Marco and Baudin, Emmanuel and Galopin, Elisabeth and Bloch, Jacqueline and Lemaitre, Aristide and Leung, P. T. and Roussignol, Philippe and Binder, Rolf and Tignon, Jerome and Schumacher, Stefan}}, issn = {{2045-2322}}, journal = {{Scientific Reports}}, title = {{{Formation and control of Turing patterns in a coherent quantum fluid}}}, doi = {{10.1038/srep03016}}, year = {{2013}}, } @article{15868, author = {{Luk, M. H. and Tse, Y. C. and Kwong, N. H. and Leung, P. T. and Lewandowski, Przemyslaw and Binder, R. and Schumacher, Stefan}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, title = {{{Transverse optical instability patterns in semiconductor microcavities: Polariton scattering and low-intensity all-optical switching}}}, doi = {{10.1103/physrevb.87.205307}}, year = {{2013}}, } @article{15871, abstract = {{We derive a transparent and easy-to-use analytic expression for the selection rules and the optical dipole matrix elements for carbon nanotubes of arbitrary chirality in the presence of axial magnetic fields using a single-orbital π-electron tight-binding model. From this, we calculate the linear absorption spectrum for arbitrary polarization directions of the incident light, providing insight into all optically allowed transition. We show that the transverse absorption peaks can be selectively excited with circularly polarized light and spectrally resolved in an axial magnetic field.}}, author = {{Liu, Hong and Schumacher, Stefan and Meier, Torsten}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, number = {{3}}, title = {{{Selection rules and linear absorption spectra of carbon nanotubes in axial magnetic fields}}}, doi = {{10.1103/physrevb.88.035429}}, volume = {{88}}, year = {{2013}}, } @article{15870, author = {{Ling, Sanliang and Schumacher, Stefan and Galbraith, Ian and Paterson, Martin J.}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, pages = {{6889--6895}}, title = {{{Excited-State Absorption of Conjugated Polymers in the Near-Infrared and Visible: A Computational Study of Oligofluorenes}}}, doi = {{10.1021/jp401359a}}, year = {{2013}}, } @article{13819, author = {{Riefer, A. and Sanna, S. and Schmidt, Wolf Gero}}, issn = {{0015-0193}}, journal = {{Ferroelectrics}}, pages = {{78--85}}, title = {{{LiNb1-xTaxO3Electronic Structure and Optical Response fromFirst-PrinciplesCalculations}}}, doi = {{10.1080/00150193.2013.821904}}, volume = {{447}}, year = {{2013}}, } @inbook{18475, abstract = {{The frequency-dependent dielectric function and the second-order polarizability tensor of ferroelectric LiNbO3 are calculated from first principles. The calculations are based on the electronic structure obtained from density-functional theory. The subsequent application of the GW approximation to account for quasiparticle effects and the solution of the Bethe–Salpeter equation yield a dielectric function for the stoichiometric material that slightly overestimates the absorption onset and the oscillator strength in comparison with experimental measurements. Calculations at the level of the independent-particle approximation indicate that these deficiencies are at least partially related to the neglect of intrinsic defects typical for the congruent material. The second-order polarizability calculated within the independent-particle approximation predicts strong nonlinear coefficients for photon energies above 1.5 eV. The comparison with measured data suggests that self-energy effects improve the agreement between experiment and theory. The intrinsic defects of congruent samples reduce the optical nonlinearities, in particular for the 21 and 31 tensor components, further improving the agreement with measured data.}}, author = {{Riefer, Arthur and Rohrmüller, Martin and Landmann, Marc and Sanna, Simone and Rauls, Eva and Vollmers, Nora Jenny and Hölscher, Rebecca and Witte, Matthias and Li, Yanlu and Gerstmann, Uwe and Schindlmayr, Arno and Schmidt, Wolf Gero}}, booktitle = {{High Performance Computing in Science and Engineering ‘13}}, editor = {{Nagel, Wolfgang E. and Kröner, Dietmar H. and Resch, Michael M.}}, isbn = {{978-3-319-02164-5}}, pages = {{93--104}}, publisher = {{Springer}}, title = {{{Lithium niobate dielectric function and second-order polarizability tensor from massively parallel ab initio calculations}}}, doi = {{10.1007/978-3-319-02165-2_8}}, year = {{2013}}, } @inproceedings{15985, author = {{Reuter, Corin and Frantz, Meike and Lauter, Christian and Block, Holger and Tröster, Thomas}}, location = {{Turin, Italy}}, title = {{{Simulation and testing of hybrid structures consisting of press-hardened steel and CFRP}}}, year = {{2012}}, } @inproceedings{15987, author = {{Lauter, Christian and Frantz, Meike and Kohler, J. P. and Tröster, Thomas}}, location = {{Venice, Italy}}, title = {{{Crash tests of hybrid structures consisting of sheet metal and local CFRP reinforcements}}}, year = {{2012}}, } @article{22953, abstract = {{The generation of specific high harmonics for an optical two-level system is elucidated. The desired emitted radiation can be induced by a carefully designed excitation pulse, which is found by a multiparameter optimization procedure. The presented mechanism can also be applied to semiconductor structures for which the calculations result in much higher emission frequencies. The optimization procedure is either performed using a genetic algorithm or a rigorous mathematical optimization technique.}}, author = {{Reichelt, Matthias and Walther, Andrea and Meier, Torsten}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, number = {{2}}, title = {{{Tailoring the high-harmonic emission in two-level systems and semiconductors by pulse shaping}}}, doi = {{10.1364/josab.29.000a36}}, volume = {{29}}, year = {{2012}}, } @inproceedings{15986, author = {{Gorny, B. and Hankeln, Frederik and Lauter, Christian and Schmidt, H. C. and Damerow, U. and Mahnken, Rolf and Maier, H. J. and Tröster, Thomas and Homberg, Werner}}, location = {{Turin, Italy}}, title = {{{Simulation and manufacturing of deep drawn parts reinforced by carbon fibre prepregs}}}, year = {{2012}}, } @article{13546, author = {{Riefer, A. and Rauls, E. and Schmidt, Wolf Gero and Eberhard, J. and Stoll, I. and Mattay, J.}}, issn = {{1098-0121}}, journal = {{Physical Review B}}, number = {{16}}, title = {{{2-Aminopyrimidine-silver(I) based organic semiconductors: Electronic structure and optical response}}}, doi = {{10.1103/physrevb.85.165202}}, volume = {{85}}, year = {{2012}}, }