We report for the first time, the synthesis and X-ray diffraction studies of single crystals of BeF(2). The crystals were obtained during the sublimation of amorphous BeF(2) under static reduced pressure. BeF(2) crystallizes in the chiral trigonal space group P3(1)21. A single-crystal X-ray diffraction study on these crystals shows that each of the Be atoms is bonded to four F atoms, and each of the F atoms is bonded to two Be atoms with associated Be-F bond distances of 1.5420(13) and 1.5471(13) Å, showing an almost regular tetrahedron. The infrared spectrum of these crystals recorded at room temperature shows distinct peaks around 770 and 410 cm(-1).
Anin situhigh pressure-FTIR study on a 2,3-dichlorobenzylidine-4-bromoaniline elastic crystal shows significant structural changes at high pressure which revert back to the ambient structure on decompression.
Organic crystals
possessing elasticity are gaining wide attention
due to their potential applications in technology. From a design perspective,
it is of utmost importance to understand the mechanical behavior of
these crystals and their ability to handle stress. In this paper,
we present an in situ high-pressure Fourier transform infrared spectroscopy
study on 2,5-dichloro-N-benzylidene-4-chloroaniline
(DPA) and 2,6 dichloro-N-benzylidene-4-fluoro-3-nitro
aniline (DFA) crystals at pressures ranging from ambient pressure
to 21.5 and 14.5 GPa respectively along with nanoindentation studies,
at room temperature. The infrared stretching wavenumber of the aromatic
and aliphatic C–H, H–CN, and C–Cl bands
on compression showed blueshifts and increased widths, which reflect
structure perturbation caused by changes in intermolecular interactions
in the crystals. It was noted that both crystals DPA and DFA behave
in a different fashion under high-pressure prompting the derivation
of different models based on structural changes in the lattice. Further,
nanoindentation studies corroborated pressure-induced molecular movement
in both crystals.
(p-Chloroanilinium)2CuCl4(C2H14Cl6CuN2) is from an important family of organic-inorganic layered hybrid compounds which can be a possible candidate for multiferroicity. In situ high pressure FTIR, Raman and resistivity measurements on this compound indicate the weakening of Jahn-Teller distortion and the consequent removal of puckering of the CuCl6(4-) octahedra within the layer. These effects trigger insulator to semiconductor phase transition along with a change in the sample colour from yellow to dark red. This article explains the crucial role of the anisotropic volume reduction of the CuCl6(4-) octahedron (caused due to the quenching of Jahn-Teller distortion) in the observed insulator to semiconductor phase transition.
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