@article{BreternitzSchorr2021,
  author    = {Breternitz, Joachim and Schorr, Susan},
  title     = {Symmetry relations in wurtzite nitrides and oxide nitrides and the curious case of Pmc2(1)},
  series = {Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances},
  volume    = {77},
  journal   = {Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances},
  number    = {3},
  publisher = {Blackwell},
  address   = {Oxford [u.a.]},
  issn      = {2053-2733},
  doi       = {10.1107/S2053273320015971},
  pages     = {208 -- 216},
  year      = {2021},
  abstract  = {Binary III-V nitrides such as AlN, GaN and InN in the wurtzite-type structure have long been considered as potent semiconducting materials because of their optoelectronic properties, amongst others. With rising concerns over the utilization of scarce elements, a replacement of the trivalent cations by others in ternary and multinary nitrides has led to the development of different variants of nitrides and oxide nitrides crystallizing in lower-symmetry variants of wurtzite. This work presents the symmetry relationships between these structural types specific to nitrides and oxide nitrides and updates some prior work on this matter. The non-existence of compounds crystallizing in Pmc2(1), formally the highest subgroup of the wurtzite type fulfilling Pauling's rules for 1:1:2 stoichiometries, has been puzzling scientists for a while; a rationalization is given, from a crystallographic basis, of why this space group is unlikely to be adopted.},
  language  = {en}
}
@inproceedings{BreternitzSchorr2021,
  author    = {Breternitz, Joachim and Schorr, Susan},
  title     = {Halide perovskites},
  series = {Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances},
  volume    = {77},
  booktitle = {Acta crystallographica / International Union of Crystallography. Section A, Foundations and advances},
  number    = {Suppl.},
  publisher = {Blackwell},
  address   = {Oxford [u.a.]},
  issn      = {2053-2733},
  doi       = {10.1107/S0108767321089479},
  pages     = {C750 -- C750},
  year      = {2021},
  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}
}
@article{FranzToebbensLehmannetal.2020,
  author    = {Franz, Alexandra and T{\"o}bbens, Daniel M. and Lehmann, Frederike and K{\"a}rgell, Martin and Schorr, Susan},
  title     = {The influence of deuteration on the crystal structure of hybrid halide perovskites: a temperature-dependent neutron diffraction study of FAPbBr(3)},
  series = {Acta crystallographica; Section B, Structural science, crystal engineering and materials},
  volume    = {76},
  journal   = {Acta crystallographica; Section B, Structural science, crystal engineering and materials},
  number    = {2},
  publisher = {Wiley-Blackwell},
  address   = {Oxford [u.a.]},
  issn      = {2052-5206},
  doi       = {10.1107/S2052520620002620},
  pages     = {267 -- 274},
  year      = {2020},
  abstract  = {This paper discusses the full structural solution of the hybrid perovskite formamidinium lead tribromide (FAPbBr(3)) and its temperature-dependent phase transitions in the range from 3 K to 300 K using neutron powder diffraction and synchrotron X-ray diffraction. Special emphasis is put on the influence of deuteration on formamidinium, its position in the unit cell and disordering in comparison to fully hydrogenated FAPbBr(3). The temperature-dependent measurements show that deuteration critically influences the crystal structures, i.e. results in partially-ordered temperature-dependent structural modifications in which two symmetry-independent molecule positions with additional dislocation of the molecular centre atom and molecular angle inclinations are present.},
  language  = {en}
}
@article{BreternitzLehmannBarnettetal.2019,
  author    = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan},
  title     = {Role of the Iodide-methylammonium interaction in the ferroelectricity of CH3NH3PbI3},
  series = {Angewandte Chemie - international edition},
  volume    = {59},
  journal   = {Angewandte Chemie - international edition},
  number    = {1},
  publisher = {John Wiley \& Sons, Inc.},
  address   = {New Jersey},
  pages     = {5},
  year      = {2019},
  abstract  = {Excellent conversion efficiencies of over 20\% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3NH3PbI3 being an archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions.},
  language  = {en}
}
@misc{BreternitzLehmannBarnettetal.2019,
  author    = {Breternitz, Joachim and Lehmann, Frederike and Barnett, Sarah A. and Nowell, Harriott and Schorr, Susan},
  title     = {Role of the Iodide-methylammonium interaction in the ferroelectricity of CH3NH3PbI3},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51822},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-518227},
  pages     = {7},
  year      = {2019},
  abstract  = {Excellent conversion efficiencies of over 20\% and facile cell production have placed hybrid perovskites at the forefront of novel solar cell materials, with CH3NH3PbI3 being an archetypal compound. The question why CH3NH3PbI3 has such extraordinary characteristics, particularly a very efficient power conversion from absorbed light to electrical power, is hotly debated, with ferroelectricity being a promising candidate. This does, however, require the crystal structure to be non-centrosymmetric and we herein present crystallographic evidence as to how the symmetry breaking occurs on a crystallographic and, therefore, long-range level. Although the molecular cation CH3NH3+ is intrinsically polar, it is heavily disordered and this cannot be the sole reason for the ferroelectricity. We show that it, nonetheless, plays an important role, as it distorts the neighboring iodide positions from their centrosymmetric positions.},
  language  = {en}
}
@article{FranzToebbensSteckhanetal.2018,
  author    = {Franz, Alexandra and T{\"o}bbens, Daniel M. and Steckhan, Julia and Schorr, Susan},
  title     = {Determination of the miscibility gap in the solid solutions series of methylammonium lead iodide/chloride},
  series = {Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials},
  volume    = {74},
  journal   = {Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials},
  publisher = {International Union of Crystallography},
  address   = {Chester},
  issn      = {2052-5206},
  doi       = {10.1107/S2052520618010764},
  pages     = {445 -- 449},
  year      = {2018},
  abstract  = {Perovskites are widely known for their enormous possibility of elemental substitution, which leads to a large variety of physical properties. Hybrid perovskites such as CH3NH3PbI3 (MAPbI(3)) and CH3NH3PbCl3 (MAPbCl(3)) are perovskites with an A([XII])B([VI)X(-)([II)(])structure, where A is an organic molecule, B is a lead(II) cation and X is a halide anion of iodine or chlorine. Whereas MAPbCl(3) crystallizes in the cubic space group Pm (3) over barm, MAPbI(3) is in the tetragonal space group I4/mcm. The substitution of I by Cl leads to an increased tolerance against humidity but is challenging or even impossible due to their large difference in ionic radii. Here, the influence of an increasing Cl content in the reaction solution on the miscibility of the solid solution members is examined systematically. Powders were synthesized by two different routes depending on the I:Cl ratio. High-resolution synchrotron X-ray data are used to establish values for the limits of the miscibility gap which are 3.1 (1.1) mol\% MAPbCl(3) in MAPI(3) and 1.0 (1) mol\% MAPbI(3) in MAPCl. The establishment of relations between average pseudo-cubic lattice parameters for both phases allows a determination of the degree of substitution from the observed lattice parameters.},
  language  = {en}
}
@article{LehmannFranzToebbensetal.2019,
  author    = {Lehmann, Frederike and Franz, Alexandra and Toebbens, Daniel M. and Levcenco, Sergej and Unold, Thomas and Taubert, Andreas and Schorr, Susan},
  title     = {The phase diagram of a mixed halide (Br, I) hybrid perovskite obtained by synchrotron X-ray diffraction},
  series = {RSC Advances},
  volume    = {9},
  journal   = {RSC Advances},
  number    = {20},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2046-2069},
  doi       = {10.1039/c8ra09398a},
  pages     = {11151 -- 11159},
  year      = {2019},
  abstract  = {By using synchrotron X-ray powder diffraction, the temperature dependent phase diagram of the hybrid perovskite tri-halide compounds, methyl ammonium lead iodide (MAPbI3, MA+ = CH3NH3+) and methyl ammonium lead bromide (MAPbBr3), as well as of their solid solutions, has been established. The existence of a large miscibility gap between 0.29 ≤ x ≤ 0.92 (±0.02) for the MAPb(I1-xBrx)3 solid solution has been proven. A systematic study of the lattice parameters for the solid solution series at room temperature revealed distinct deviations from Vegard's law. Furthermore, temperature dependent measurements showed that a strong temperature dependency of lattice parameters from the composition is present for iodine rich compositions. In contrast, the bromine rich compositions show an unusually low dependency of the phase transition temperature from the degree of substitution.},
  language  = {en}
}
@article{SchuckLehmannOllivieretal.2019,
  author    = {Schuck, G{\"o}tz and Lehmann, Frederike and Ollivier, Jacques and Mutka, Hannu and Schorr, Susan},
  title     = {Influence of chloride substitution on the rotational dynamics of methylammonium in MAPbI(3-x)Cl(x) perovskites},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {123},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  number    = {18},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.9b01238},
  pages     = {11436 -- 11446},
  year      = {2019},
  abstract  = {Hybrid halide perovskites, MAPbI(3), MAPbI(2.94)Cl(0.0)6, and MAPbCl(3) (MA, methylammonium), were investigated using inelastic and quasielastic neutron scattering (QENS) with the aim of elucidating the impact of chloride substitution on the rotational dynamics of MA. In this context, we discuss the influence of the inelastic neutron scattering caused by low-energy phonons on QENS, resulting from the MA rotational dynamics in MAPbI(3-x)Cl(x). Through a comparative temperature-dependent QENS investigation with different energy resolutions, which allow a wide Fourier time window, we achieved a consistent description of the influence of chlorine substitution in MAPbI(3) on the MA dynamics. Our results showed that chlorine substitution in the low-temperature orthorhombic phase leads to a weakening of the hydrogen bridge bonds, since the characteristic relaxation times of C-3 rotation at 70 K in MAPbCl(3) (135 ps) and MAPbI(2.94)Cl(0.06) (485 ps) are much shorter than that in MAPbI(3) (1635 ps). For the orthorhombic phase, we obtained the activitin energies from the temperature-dependent characteristic relaxation times tau (c3). by Arrhenius fits, indicating lower values of E-a for MAPbCl(3) and MAPbI(2.94)Cl(0.06) compared to that of MAPbI(3). We also performed QENS analyses at 190 K for all three samples. Here, we observed that MAPbCI(3) shows slower MA rotational dynamics than MAPbI(3) in the disordered structure.},
  language  = {en}
}