scholarly journals Cubic crystals in an x-ray polarization-splitting geometry

2020 ◽  
Vol 91 (2) ◽  
pp. 023105
Author(s):  
M. S. Wallace ◽  
R. Presura ◽  
S. Haque ◽  
I. Pohl ◽  
P. Lake ◽  
...  
Keyword(s):  
Cubic Crystals ◽  
X Ray ◽  
Polarization Splitting

scholarly journals X-ray photoelectron spectra of iron-sulphur proteins

1975 ◽  
Vol 149 (2) ◽  
pp. 471-474 ◽  
Author(s):  
P T Andrews ◽  
C E Johnson ◽  
B Wallbank ◽  
R Cammack ◽  
D O Hall ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic State ◽  
High Potential ◽  
Spin Coupling ◽  
Photoelectron Spectra ◽  
Clostridium Pasteurianum ◽  
Active Centre ◽  
Core Polarization ◽  
X Ray ◽  
Polarization Splitting

The X-ray photoelectron spectra of the 2p, 3s and 3p levels of iron in oxidized Clostridium pasteurianum ferredoxin indicate that the eight iron atoms in the molecule are indistinguishable. Their magnetic state is indicated both by core polarization splitting of the 3s electrons, and by ‘shake-up’ satellites on the 2p lines. Similar satellites are observed in the 2p lines of reduced Chromatium high-potential iron-sulphur proteins and oxidized spinach ferredoxin, indicating that there too the iron atoms are magnetic. The low observed magnetic susceptibility of these proteins is therefore due to spin-coupling between the iron atoms in the active centre.

Natropharmacoalumite, NaAl4[(OH)4(AsO4)3].4H2O, a new mineral of the pharmacosiderite supergroup and the renaming of aluminopharmacosiderite to pharmacoalumite

2010 ◽  
Vol 74 (5) ◽  
pp. 929-936 ◽  
Author(s):  
M. S. Rumsey ◽  
S. J. Mills ◽  
J. Spratt
Keyword(s):  
Empirical Formula ◽  
Direct Methods ◽  
Structure Type ◽  
New Mineral ◽  
Gold Mine ◽  
Nomenclature System ◽  
Cubic Crystals ◽  
X Ray ◽  
Mohs Hardness ◽  
Dominant Cation

AbstractNatropharmacoalumite, ideally NaAl4[(OH)4(AsO4)3]·4H2O, is a new mineral from the Maria Josefa Gold mine, Rodalquilar, Andalusia region, Spain. It occurs as colourless, intergrown cubic crystals with chenevixite, kaolinite, jarosite and indeterminable mixtures of Fe and Sb oxyhydroxides. Individual crystals are up to 0.5 mm on edge, although crystals are more commonly ˜0.25 mm across and occur in patchy aggregates several millimetres across. The mineral is transparent with a vitreous to adamantine lustre. It is brittle with an imperfect cleavage, irregular fracture and a white streak. The Mohs hardness is ˜2.5 with a calculated densityof 2.56 g cm–3 for the empirical formula. Electron microprobe analyses yielded Na2O 2.52%, K2O 1.49%, Al2O3 29.50%, As2O5 48.84% and H2O was calculated in line with the structural analysis as 16.28% totalling 98.63%. The empirical formula, based upon 20.21 oxygen atoms, is [Na0.57K0.22(H3O)0.21]Σ1.00Al4.05(As2.97O12)(OH)4·4H2O. The five strongest lines in the X-ray powder diffraction pattern are [dobs(Å), Iobs,(hkl)]: 7.759,100,(100); 4.473,40,(111); 3.870,50,(200); 2.446,9,(301); 2.331,12,(311). Natropharmacoalumite is cubic, space group with a = 7.7280(3) Å, V = 461.53(3) Å3 and Z = 1. The crystal structure was solved by direct methods and refined to R1 = 0.063 for 295 reflections with F>4σ(F). The structure conforms broadly to that of the general pharmacosiderite structure type, with Na as the dominant cation in cavities of strongly distorted Al octahedra and As tetrahedra. A new group nomenclature system for minerals with the pharmacosiderite structure has been established, including the renaming of aluminopharmacosiderite to pharmacoalumite.

Mendeleevite-(Nd), (Cs,□)6 (□,Cs)6 (□,K)6 (REE,Ca)30(Si70O175)(OH,H2O,F)35, a new mineral from the Darai-Pioz alkaline massif, Tajikistan

2017 ◽  
Vol 81 (1) ◽  
pp. 135-141 ◽  
Author(s):  
Atali A. Agakhanov ◽  
Leonid A. Pautov ◽  
Elena Sokolova ◽  
Frank C. Hawthorne ◽  
Vladimir Yu Karpenko ◽  
...  
Keyword(s):  
Chemical Elements ◽  
New Mineral ◽  
X Ray Diffraction ◽  
Cubic Crystals ◽  
X Ray ◽  
Pyrochlore Group ◽  
The World ◽  
Mohs Hardness ◽  
Alkaline Massif ◽  
Measured Density

AbstractMendeleevite-(Nd), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca)30(Si70O175)(OH,H2O,F)35 is a new mineral from the Darai-Pioz alkaline massif, Tajikistan. Mendeleevite-(Nd) was found in a pectolite aggregate in silexites (quartz-rich rocks) which consist of fine to medium pectolite grains, quartz, aegirine and fluorite, with minor khvorovite, mendeleevite-(Ce), sokolovaite, hyalotekite, orlovite, kirchhoffite, pekovite, neptunite, zeravshanite, senkevichite, nordite-(Nd), alamosite, pyrochlore-group minerals and baratovite. Mendeleevite-(Nd) forms colourless cubic crystals 10–40 μm in size; it has a vitreous lustre and a Mohs hardness of 5–5.5; Dmeas. = 3.20(2) g/cm3, Dcalc. = 3.155 g/cm3. Mendeleevite-(Nd) is optically isotropic, with the refractive index n = 1.582(2). Mendeleevite-(Nd) is cubic, space group Pm3̄, a = 21.9106(4) Å; Z = 2. The six strongest reflections in the powder X-ray diffraction pattern are [d (Å), I (%), (h k l)] are: 11.01, 100, (0 0 2); 15.63, 55, (0 1 1); 3.47, 42, (2 0 6); 3.099, 42, (3 4 5); 2.192, 42, (0 0 10); 1.819, 41, (3 6 10). Chemical analysis by electron microprobe gave SiO2 42.30, Ce2O3 10.12, La2O3 3.60, Nd2O3 16.19, Pr2O3 2.79, Sm2O3 4.19, Gd2O3 1.69, Eu2O3 0.47, SrO 2.99, CaO 2.20, Cs2O 8.50, K2O 0.85, H2O 3.85, F 1.25, –O = F2 –0.53, sum 100.46 wt.%, with H2O calculated by analogy with mendeleevite-(Ce). The empirical formula based on 210 (O + F) apfu, with F + OH + H2O = 35 pfu, is Cs6(□4.20K1.80)∑6{[(Nd9.57Ce6.13Sm2.39La2.20Pr1.68Gd0.93Eu0.27)∑23.17(Ca3.90Sr2.87)∑6.77]∑29.94□0.06}∑30(Si70.03O175)(OH14.47F6.54)∑21.01 (H2O)14, Z = 2. The simplified and ideal formulae are (Cs,□)6 (□,Cs)6(□,K)6 (REE,Ca)30 (Si70O175)(OH, H2O,F)35 and Cs6(REE23Ca7)(Si70O175)(OH,F)19(H2O)16, respectively. The compatibility index (from measured density) = – 0.039 (excellent). Mendeleevite-(Nd) is a Nd analogue of mendeleevite-(Ce), (Cs,□)6(□,Cs)6(□,K)6(REE,Ca,□)30(Si70O175)(H2O,OH,F,□)35. Both minerals are named after Dmitri Mendeleev (1834–1907), the great Russian chemist, author of the periodic table of chemical elements, who has had a significant impact on the development of natural sciences and industry, both in Russia and around the world.

scholarly journals Polarization splitting with cubic crystals evaluated with synchrotron radiation

2021 ◽  
Vol 92 (10) ◽  
pp. 103101
Author(s):  
M. S. Wallace ◽  
S. H. Haque ◽  
R. Presura ◽  
I. Pohl ◽  
M. Wojcik
Keyword(s):  
Synchrotron Radiation ◽  
Cubic Crystals ◽  
Polarization Splitting
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