468,006 research outputs found
Structural response to O*-O' and magnetic transitions in orthorhombic perovskites
We present a temperature dependent single crystal x-ray diffraction study of
twinned orthorhombic perovskites La1-xCaxMnO3, for x=0.16 and x=0.25. These
data show the evolution of the crystal structure from the ferromagnetic
insulating state to the ferromagnetic metallic state. The data are modelled in
space group Pnma with twin relations based on a distribution of the b axis over
three perpendicular cubic axes. The twin model allows full structure
determination in the presence of up to six twin fractions using the single
crystal x-ray diffraction data.Comment: 13 pages, including 13 figures and 2 table
Raman Spectroscopic and SEM Analysis of Sodium-Zippeite
Raman at 298 and 77 K and infrared spectra of two samples of sodium-zippeite were studied and interpreted. U-O bond lengths in uranyl were calculated and compared with those inferred from the X-ray single crystal structure data of a synthetic sodium-zippeite analog. Hydrogen-bonding network in the studied samples is discussed. O-H…O bond lengths were calculated and compared with those predicted from the X-ray single crystal structure analysis
The crystal structure of dipotassium tetranitroethide
Crystal structure of dipotassium tetranitroethide determined by single crystal X-ray diffraction technique
Application of relativistic scattering theory of x rays to diffraction anomalous fine structure in Cu
We apply our recent first-principles formalism of magnetic scattering of circularly polarized x rays to a single Cu crystal. We demonstrate the ability of our formalism to interpret the crystalline environment related near-edge fine structure features in the resonant x-ray scattering spectra at the Cu K absorption edge. We find good agreement between the computed and measured diffraction anomalous fine structure features of the x-ray scattering spectra
New complexes with M-Si-O or M-Si-S linkages (M = Fe or Co)
Ph2XSiFe(CO)2Cp [X = p-tolylS (1a), MeO (1b)] and Ph[2-MeOC6H4]XSiFe(CO)2Cp [X = Cl (2a), OMe (2b)] have been fully characterised, including X-ray crystal structure determinations for 1a, 1b and 2a. None of the examples showed any tendency for migration of the X groups from silicon to iron, with elimination of silylene. However very ready loss of the X groups was seen in the electrospray mass spectra, suggesting formation of the cationic silylene-iron complex ions is favoured. This was especially so for 2a and 2b, where intramolecular stabilisation of the silicon centre from the 2-OMe group is possible.The stable siloxane O[SiPh2{Co(CO)4}]2 was also characterised; the X-ray crystal structure analysis shows a Si-O-Si bond angle of 153°
Unusual Low-Temperature Phase in VO Nanoparticles
We present a systematic investigation of the crystal and electronic structure
and the magnetic properties above and below the metal-insulator transition of
ball-milled VO nanoparticles and VO microparticles. For this research,
we performed a Rietveld analysis of synchrotron radiation x-ray diffraction
data, O x-ray absorption spectroscopy, V resonant inelastic x-ray
scattering, and magnetic susceptibility measurements. This study reveals an
unusual low-temperature phase that involves the formation of an elongated and
less-tilted V-V pair, a narrowed energy gap, and an induced paramagnetic
contribution from the nanoparticles. We show that the change in the crystal
structure is consistent with the change in the electronic states around the
Fermi level, which leads us to suggest that the Peierls mechanism contributes
to the energy splitting of the state. Furthermore, we find that the
high-temperature rutile structure of the nanoparticles is almost identical to
that of the microparticles.Comment: 7 pages, 8 figures, 2 table
Synthesis and structure of the inclusion complex {NdQ[5]K@Q[10](H₂O)4}·4NO₃·20H₂O
Heating a mixture of Nd(NO₃)₃·6H₂O, KCl, Q[10] and Q[5] in HCl for 10 min affords the inclusion complex {NdQ[5]K@Q[10](H₂O)₄}·4NO₃·20H₂O. The structure of the inclusion complex has been investigated by single crystal X-ray diffraction and by X-ray Photoelectron spectroscopy (XPS)
Collimation of electron and X-ray beams using zeolite crystals
Zeolite crystals can be used to collimate electron and X-ray beams. Faujasite, naturally occuring crystal in this group, provides structure necessary for collimation
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