@article{Fritsch2022, author = {Fritsch, Daniel}, title = {Revisiting the Cu-Zn disorder in kesterite type Cu2ZnSnSe4 employing a novel approach to hybrid functional calculations}, series = {Applied Sciences : open access journal}, volume = {12}, journal = {Applied Sciences : open access journal}, number = {5}, publisher = {MDPI}, address = {Basel}, issn = {2076-3417}, doi = {10.3390/app12052576}, pages = {10}, year = {2022}, abstract = {In recent years, the search for more efficient and environmentally friendly materials to be employed in the next generation of thin film solar cell devices has seen a shift towards hybrid halide perovskites and chalcogenide materials crystallising in the kesterite crystal structure. Prime examples for the latter are Cu2ZnSnS4, Cu2ZnSnSe4, and their solid solution Cu2ZnSn(SxSe1-x)(4), where actual devices already demonstrated power conversion efficiencies of about 13 \%. However, in their naturally occurring kesterite crystal structure, the so-called Cu-Zn disorder plays an important role and impacts the structural, electronic, and optical properties. To understand the influence of Cu-Zn disorder, we perform first-principles calculations based on density functional theory combined with special quasirandom structures to accurately model the cation disorder. Since the electronic band gaps and derived optical properties are severely underestimated by (semi)local exchange and correlation functionals, supplementary hybrid functional calculations have been performed. Concerning the latter, we additionally employ a recently devised technique to speed up structural relaxations for hybrid functional calculations. Our calculations show that the Cu-Zn disorder leads to a slight increase in the unit cell volume compared to the conventional kesterite structure showing full cation order, and that the band gap gets reduced by about 0.2 eV, which is in very good agreement with earlier experimental and theoretical findings. Our detailed results on structural, electronic, and optical properties will be discussed with respect to available experimental data, and will provide further insights into the atomistic origin of the disorder-induced band gap lowering in these promising kesterite type materials.}, language = {en} } @article{SerranoMunozFritschMishurovaetal.2020, author = {Serrano-Munoz, Itziar and Fritsch, Tobias and Mishurova, Tatiana and Trofimov, Anton and Apel, Daniel and Ulbricht, Alexander and Kromm, Arne and Hesse, Rene and Evans, Alexander and Bruno, Giovanni}, title = {On the interplay of microstructure and residual stress in LPBF IN718}, series = {Journal of materials science}, volume = {56}, journal = {Journal of materials science}, number = {9}, publisher = {Springer}, address = {New York}, issn = {0022-2461}, doi = {10.1007/s10853-020-05553-y}, pages = {5845 -- 5867}, year = {2020}, abstract = {The relationship between residual stresses and microstructure associated with a laser powder bed fusion (LPBF) IN718 alloy has been investigated on specimens produced with three different scanning strategies (unidirectional Y-scan, 90 degrees XY-scan, and 67 degrees Rot-scan). Synchrotron X-ray energy-dispersive diffraction (EDXRD) combined with optical profilometry was used to study residual stress (RS) distribution and distortion upon removal of the specimens from the baseplate. The microstructural characterization of both the bulk and the near-surface regions was conducted using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). On the top surfaces of the specimens, the highest RS values are observed in the Y-scan specimen and the lowest in the Rot-scan specimen, while the tendency is inversed on the side lateral surfaces. A considerable amount of RS remains in the specimens after their removal from the baseplate, especially in the Y- and Z-direction (short specimen dimension and building direction (BD), respectively). The distortion measured on the top surface following baseplate thinning and subsequent removal is mainly attributed to the amount of RS released in the build direction. Importantly, it is observed that the additive manufacturing microstructures challenge the use of classic theoretical models for the calculation of diffraction elastic constants (DEC) required for diffraction-based RS analysis. It is found that when the Reuss model is used for the calculation of RS for different crystal planes, as opposed to the conventionally used Kroner model, the results exhibit lower scatter. This is discussed in context of experimental measurements of DEC available in the literature for conventional and additively manufactured Ni-base alloys.}, language = {en} } @article{KatzenmaierFritschBronstert2000, author = {Katzenmaier, Daniel and Fritsch, Uta and Bronstert, Axel}, title = {Influences of land-use and land-cover changes on storm-runoff generation}, year = {2000}, language = {en} } @article{BronstertFritschKatzenmaieretal.2000, author = {Bronstert, Axel and Fritsch, Uta and Katzenmaier, Daniel and Bismuth, Christine}, title = {Quantification of the influence of the land-surface and river training on flood discharge of the Rhine Basin}, year = {2000}, language = {en} } @article{BardossyBronstertBuiteveldetal.2000, author = {B{\´a}rdossy, Andras and Bronstert, Axel and Buiteveld, Hendrik and Disse, Markus and Fritsch, Uta and Katzenmaier, Daniel and Lammersen, Rita}, title = {Influence of the land surface and river training on flood conditions in the Rhine basin}, year = {2000}, language = {en} } @article{FritschKatzenmaierBronstert2000, author = {Fritsch, Uta and Katzenmaier, Daniel and Bronstert, Axel}, title = {Land-use and land-cover scenarios for flood risk analysis and river basin management}, year = {2000}, language = {en} } @article{BronstertKatzenmaierFritsch2000, author = {Bronstert, Axel and Katzenmaier, Daniel and Fritsch, Uta}, title = {Hochwasserproblematik und der Zusammenhang mit Landnutzungs- und Klima{\"a}nderungen}, year = {2000}, language = {de} } @article{KatzenmaierFritschBronstert2001, author = {Katzenmaier, Daniel and Fritsch, Uta and Bronstert, Axel}, title = {Quantifizierung des Einflusses von Landnutzung und dezentraler Versickerung auf die Hochwasserentstehung}, isbn = {3-503-06021-9}, year = {2001}, language = {de} } @article{BronstertFritschLeonhardtetal.2001, author = {Bronstert, Axel and Fritsch, Uta and Leonhardt, H. and Niehoff, Daniel}, title = {Quantifizierung des Einflusses von Landnutzungs- und Klima{\"a}nderungen auf die Hochwasserentstehung am Beispiel ausgew{\"a}hlter Flussgebiete}, year = {2001}, language = {de} } @article{NiehoffFritschBronstert2002, author = {Niehoff, Daniel and Fritsch, Uta and Bronstert, Axel}, title = {Land-use impacts on storm-runoff generation : scenarios of land-use change and simulation of hydrological response in a meso-scale catchment in SW-Germany}, year = {2002}, language = {en} } @article{WangFritschBerendtsetal.2021, author = {Wang, Zhenyu and Fritsch, Daniel and Berendts, Stefan and Lerch, Martin and Breternitz, Joachim and Schorr, Susan}, title = {Elucidation of the reaction mechanism for the synthesis of ZnGeN2 through Zn2GeO4 ammonolysis}, series = {Chemical science / RSC, Royal Society of Chemistry}, volume = {12}, journal = {Chemical science / RSC, Royal Society of Chemistry}, number = {24}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {2041-6539}, doi = {10.1039/d1sc00328c}, pages = {8493 -- 8500}, year = {2021}, abstract = {Ternary II-IV-N-2 materials have been considered as a promising class of materials that combine photovoltaic performance with earth-abundance and low toxicity. When switching from binary III-V materials to ternary II-IV-N-2 materials, further structural complexity is added to the system that may influence its optoelectronic properties. Herein, we present a systematic study of the reaction of Zn2GeO4 with NH3 that produces zinc germanium oxide nitrides, and ultimately approach stoichiometric ZnGeN2, using a combination of chemical analyses, X-ray powder diffraction and DFT calculations. Elucidating the reaction mechanism as being dominated by Zn and O extrusion at the later reaction stages, we give an insight into studying structure-property relationships in this emerging class of materials.}, language = {en} }