octahedral cation
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Author(s):  
ALIREZA HEIDARI

Triptycene Barrelene Anthracene (TBA) is a polycyclic aromatic hydrocarbon consisting of three benzene rings. The name TBA is a composite of phenyl and TBA. In its pure form, it is found in cigarette smoke and is a known irritant, photosensitizing skin and industrial carcinogenic wastewater. Cadmium Oxide (CdO) is an inorganic compound with the formula CdO. It is one of the main precursors to other cadmium compounds. It crystallizes in a cubic rocksalt lattice-like sodium chloride, with octahedral cation and anion centers. It occurs naturally as the rare mineral monteponite. CdO can be found as a colorless amorphous powder or as brown or red crystals. CdO is an n-type semiconductor with a bandgap of 2.18 eV (2.31 eV) at room temperature (298 K). DNA/RNA, CdO and DNA/RNA–CdO sandwiched complex was characterized by Attenuated Total Reflection–Fourier Transform–Infrared (ATR–FTIR) spectroscopy, Raman spectroscopy, X–Ray Diffraction (XRD) technique and Energy–Dispersive X–Ray (EDAX) spectroscopy. The modified anti–cancer-protective membrane was characterized by Scanning Electron Microscope (SEM), EDAX analysis, 3D–Atomic–Force Microscopy (3D–AFM), Transmission Electron Microscopy (TEM) and contact angle analyses and methods. The current study is aimed to use Polysorbate 80 as a surfactant for investigating the effectiveness of permeate TBA on the Polyether Ether Ketone (PEEK) anti–cancer-protective membrane and the effect of loading DNA/RNA–CdO sandwiched complex on hydrophilicity and anti-cancer properties. The results showed decreasing surface pore size from 227 to 176 and increasing porosity from 101 to 111 with loading DNA/RNA–CdO sandwiched complex, and the permeate of anti–cancer-protective membrane increased from 80 to 220 (L/m2. hr. bar) with loading DNA/RNA–CdO sandwiched complex.


Chemistry ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 947-959
Author(s):  
Robert D. Bannister ◽  
William Levason ◽  
Gillian Reid

Bis(diphenylphosphino)methane dioxide (dppmO2) forms eight-coordinate cations [M(dppmO2)4]Cl3 (M = La, Ce, Pr, Nd, Sm, Eu, Gd) on reaction in a 4:1 molar ratio with the appropriate LnCl3 in ethanol. Similar reaction in a 3:1 ratio produced seven-coordinate [M(dppmO2)3Cl]Cl2 (M = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb), whilst LuCl3 alone produced six-coordinate [Lu(dppmO2)2Cl2]Cl. The complexes have been characterised by IR, 1H and 31P{1H}-NMR spectroscopy. X-ray structures show that [M(dppmO2)4]Cl3 (M = Ce, Sm, Gd) contain square antiprismatic cations, whilst [M(dppmO2)3Cl]Cl2 (M = Yb, Dy, Lu) have distorted pentagonal bipyramidal structures with apical Cl. The [Lu(dppmO2)2Cl2]Cl has a cis octahedral cation. The structure of [Yb(dppmO2)3(H2O)]Cl3·dppmO2 is also reported. The change in coordination numbers and geometry along the series is driven by the decreasing lanthanide cation radii, but the chloride counter anions also play a role.


2020 ◽  
pp. 1-7
Author(s):  
Anthony R. Kampf ◽  
Jakub Plášil ◽  
Barbara P. Nash ◽  
Marco E. Ciriotti ◽  
Fabrizio Castellaro ◽  
...  

Abstract Monteneroite (IMA2020-028), Cu2+Mn2+2(AsO4)2⋅8H2O, is a new vivianite-structure mineral from the Monte Nero mine, Rocchetta di Vara, La Spezia, Liguria, Italy. It is a secondary mineral that crystallised from As-, Cu- and Mn-rich fluids and it is associated with braunite, copper, cuprite, rhodochrosite and strashimirite. Monteneroite occurs as light green, thick blades up to ~2.5 mm long. The streak is white. Crystals are transparent with vitreous lustre. The mineral has Mohs hardness of 2, is somewhat sectile, exhibits two cleavages ({010} perfect and {001} fair) and has irregular stepped fracture. The measured density is 2.97(2) g cm–3. Monteneroite is optically biaxial (+), with α = 1.604(2), β = 1.637(2) and γ = 1.688(2), determined in white light; 2V = 80(1)°; slight dispersion is r < v, orientation: X = b; Z ^ c = 52° in obtuse β. Electron microprobe analyses provided the empirical formula (Cu2+0.88Mn2+0.11)Σ0.99Mn2+2.00(As1.00O4)2⋅8H2O. Monteneroite is monoclinic, C2/m, a = 10.3673(14), b = 13.713(2), c = 4.8420(8) Å, β = 105.992(8)°, V = 661.72(18) Å3 and Z = 2. Monteneroite has a vivianite-type structure (R1 = 0.0535 for 534 I > 2σI reflections). It is the first mineral with this structure type to be defined with ordered octahedral cation sites.


Author(s):  
Prasanna V. Balachandran ◽  
Toby Shearman ◽  
James Theiler ◽  
Turab Lookman

In ferroelectric perovskites, displacements of cations from the high-symmetry lattice positions in the paraelectric phase break the spatial inversion symmetry. Furthermore, the relative magnitude of ionic displacements correlate strongly with ferroelectric properties such as the Curie temperature. As a result, there is interest in predicting the relative displacements of cations prior to experiments. Here, machine learning is used to predict the average displacement of octahedral cations from its high-symmetry position in ferroelectric perovskites. Published octahedral cation displacements data from density functional theory (DFT) calculations are used to train machine learning models, where each cation is represented by features such as Pauling electronegativity, Martynov–Batsanov electronegativity and the ratio of valence electron number to nominal charge. Average displacements for ten new octahedral cations for which DFT data do not exist are predicted. Predictions are validated by comparing them with new DFT calculations and existing experimental data. The outcome of this work has implications in the design and discovery of novel ferroelectric perovskites.


2011 ◽  
Vol 01 (01) ◽  
pp. 127-134 ◽  
Author(s):  
EUNG SOO KIM ◽  
CHANG JUN JEON

Effects of crystal structures on dielectric properties of ATiO 3 (trigonal ilmenite), ATa 2 O 6 (tetragonal tri-rutile) and AWO 4 (monoclinic wolframite) (A = Ni, Mg, Co) ceramics with A- and B-site oxygen octahedra were investigated at microwave frequencies. The dielectric constant (K) of the specimens was affected by the dielectric polarizabilities of composition and cation bond valence between octahedral cation and oxygen ion per molar volume (V m ). The quality factor (Qf) of ATiO 3 was appreciably larger than those of ATa 2 O 6 and AWO 4 due to the different sharing types of oxygen octahedra. The temperature coefficient of resonant frequency (TCF) of the specimens was dependent on the octahedral distortion per V m .


2010 ◽  
Vol 66 (3) ◽  
pp. 280-291 ◽  
Author(s):  
Bernd J. Maier ◽  
Ross J. Angel ◽  
William G. Marshall ◽  
Boriana Mihailova ◽  
Carsten Paulmann ◽  
...  

We have employed a combination of powder neutron diffraction and single-crystal synchrotron X-ray diffraction to characterize the pressure-induced phase transitions that occur in the perovskite-type relaxor ferroelectric PbSc0.5Ta0.5O3 (PST) and Pb0.78Ba0.22Sc0.5Ta0.5O3 (PST-Ba). At ambient pressure the symmetry of the average structure for both compounds is Fm\bar{3}m as a result of partial ordering of the Sc and Ta cations on the octahedral sites. At pressures above the phase transition both the neutron and X-ray diffraction patterns exhibit an increase in the intensities of h,k,l = all odd reflections and no appearance of additional Bragg reflections. Synchrotron single-crystal X-ray diffraction data show that the intensity of hhh peaks, h = 2n + 1, does not change with pressure. This indicates that the structural distortion arising from the phase transition has a glide-plane pseudo-symmetry along the 〈111〉 cubic directions. Rietveld refinement to the neutron powder data shows that the high-pressure phase has either R\bar{3}c or R\bar{3} symmetry, depending on whether the presence of 1:1 octahedral cation ordering is neglected or taken into account, and comprises octahedral tilts of the type a − a − a − that continuously evolve with pressure. The cubic-to-rhombohedral transition is also marked by a large increase in the anisotropy of the displacement ellipsoids of the Pb cations, indicating larger displacements of Pb cations along the rhombohedral threefold axis rather than within the perpendicular plane. For PST the anisotropy of the Pb displacement parameters decreases at approximately 3 GPa above the phase-transition pressure. For both PST and PST-Ba the average magnitudes of Pb-cation displacements expressed in terms of isotropic displacement ellipsoids gradually decrease over the entire pressure range from ambient to 7.35 GPa.


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