Author: Alexandra Friedrich

Pressure-Induced Polymerization of Polycyclic Arene-Perfluoroarene Cocrystals: Single Crystal X-ray Diffraction Studies, Reaction Kinetics, and Design of Columnar Hydrofluorocarbons

Pressure-induced polymerization of aromatic compounds leads to novel materials containing sp3 carbon-bonded networks. The choice of the molecular species and the control of their arrangement in the crystal structures via intermolecular interactions, such as the arene–perfluoroarene interaction, can enable the design of target polymers. We have investigated the crystal structure compression and pressure-induced polymerization reaction kinetics of two polycyclic 1:1 arene–perfluoroarene cocrystals, naphthalene/octafluoronaphthalene (NOFN) and anthracene/octafluoronaphthalene (AOFN), up to 25 and 30 GPa, respectively, using single-crystal synchrotron X-ray diffraction, infrared spectroscopy, a…

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High-pressure phase of LaPO$_{4}$ studied by x-ray diffraction and second harmonic generation

Physical review / B 94(13), 134109 (2016). doi:10.1103/PhysRevB.94.134109

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Optical and structural study of the pressure-induced phase transition of CdWO$_4$

Physical review / B 95(17), 174105 (2017). doi:10.1103/PhysRevB.95.174105

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Phase Stability of Lanthanum Orthovanadate at High Pressure

The journal of physical chemistry / C 120(25), 13749 - 13762(2016). doi:10.1021/acs.jpcc.6b04782

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High-pressure phase ofLaPO4studied by x-ray diffraction and second harmonic generation

The pressure-induced phase transition of monazite-type ${\mathrm{LaPO}}_{4}$ at $\ensuremath{\approx}26$ GPa is studied by single-crystal x-ray diffraction and second harmonic generation (SHG) up to 31 GPa. The structure of the postmonazite phase of ${\mathrm{LaPO}}_{4}$ has been obtained and it is shown that it corresponds to a post-barite-type structure with an acentric space group $P{2}_{1}{2}_{1}{2}_{1}$. A strong increase of the SHG signal at the transition confirms that the high-pressure polymorph is noncentrosymmetric. The phase transition involves a significant discontinuous decrease of the unit-cell volume by 6%, which is mainly due to a strong contraction of the $a$ lattice parame…

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Structure Solution of the High-Pressure Phase of CuWO4 and Evolution of the Jahn–Teller Distortion

In this work, we have investigated the structural behavior of cuproscheelite up to 33.9 GPa by means of high-pressure single-crystal X-ray diffraction (SXRD) and extended X-ray absorption fine structure (EXAFS). According to EXAFS, beyond 9 GPa a phase transition takes place. On the basis of SXRD, the transition is from the triclinic (P1) structure to a monoclinic (P2/c) structure isotypic to wolframite. The transition implies abrupt changes of CuO6 and WO6 octahedra, but no coordination change. Further, we report the role played by the Jahn–Teller distortion of the CuO6 octahedra on the mechanism of the phase transition as well as the changes in the behavior of the Cu–O bonds for the tricl…

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High-pressure Raman spectroscopy and lattice-dynamics calculations on scintillating MgWO4: Comparison with isomorphic compounds

Research was financed by the Spanish Ministerio de Educacion y Ciencia (MEC) under Grants No. MAT2010-21270-C04-01/02/04, and No. CSD-2007-00045. J. R.-F. thanks the MEC for support through the FPI program, as well as the SPP1236 central facility in Frankfurt for its use. F. J. M. acknowledges support from Vicerrectorado de Investigacion y Desarrollo de la Universitat Politecnica de Valencia (UPV) (Grant No. UPV2010-0096). A. M. and P. R.-H. acknowledge the supercomputer time provided by the Red Espanola de Supercomputacion. A. F. appreciates support from the German Research Foundation (Grant No. FR2491/2-1).

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High-pressure structural phase transition inMnWO4

The pressure-induced phase transition of the multiferroic manganese tungstate MnWO4 is studied on single crystals using synchrotron x-ray diffraction and Raman spectroscopy. We observe the monoclinic P2/c to triclinic P (1) over bar phase transition at 20.1 GPa and get insight on the phase transition mechanism from the appearance of tilted triclinic domains. Selective Raman spectroscopy experiments with single crystals have shown that the onset of the phase transition occurs 5 GPa below the previously reported pressure obtained from experiments performed with powder samples.

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