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O. V. Frank-Kamenetskaya I. V. Rozhdestvenskaya L. A. Yanulova 《Journal of Structural Chemistry》2002,43(1):89-100
The crystal structures of three minerals (arsenosulvanite, V,As-germanite, and colusite) of the general crystal chemical formula
(As, Ge, Sn, Sb, V)6S32, where CuM, VM are cations at interstitial positions, 0.2 x 2.0, 2.7 y 0, (space group
, a = 10.527; 10.600; 10.653 ; R = 0.066; 0.046; 0.033) have been determined using single-crystal X-ray diffraction data. The minerals are the two structural modifications of the compound with the ideal formula V2Cu24As6S32; they differ from each other in the occupancy of the interstitial position 2a. In colusite, this position is occupied by the V5+ cations; in arsenosulvanite and V,As-germanite, by Cu2+. A characteristic feature of the structures is the presence of octahedral [
S4]Cu6 (
= V, Cu) complexes not directly interacting with each other and lying inside the Laves polyhedra. In the structures of arsenosulvanite and V,As-germanite, a sulvanite framework consisting of interpenetrating Laves polyhedra
T3S4 (
= V, Cu; T = Cu, As, Ge) has been found. The sulvanite framework is statistically distributed over the sphalerite matrix. The variable composition of the minerals is due to heterovalent isomorphism in the sphalerite position 6c. Charge disbalance arising from substitution of the pentavalent arsenic cations by cations of lower valence is compensated by the appearance of additional Cu2+ cations. The nonstoichiometry of the compositions is explained by the presence of vacancies in the interstitial and sphalerite positions. 相似文献
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I. V. Rozhdestvenskaya O. V. Frank-Kamenetskaya A. G. Shtukenberg I. I. Bannova 《Journal of Structural Chemistry》2001,42(4):628-638
The crystal structure of alum K(Al0.95Cr0.05)(SO4)212H2O possessing anomalous birefringence was refined in space groups Pa3 and P1 (a = b = c = 12.165(2) , R = 0.0587). The distortions of cubic symmetry are attributed to the peculiarities of the orientational disorder in the distribution of SO4 tetrahedra and to the different degrees of distortion of the aluminum octahedra. 相似文献
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I. V. Rozhdestvenskaya Yu. M. Bronzova O. V. Frank-Kamenetskaya A. A. Zolotarev L. G. Kuznetsova I. I. Bannova 《Crystallography Reports》2008,53(2):223-227
The crystal structure of a natural calcium-lithium-aluminum tourmaline, which has the unique composition (Ca0.62Na0.32□0.06)(Al1.08Li0.99Fe 0.66 2+ Mg0.24Ti0.03)Al6[Si6O18](BO3)3(OH2.28O0.72) · (F0.84O0.16), is refined (R = 0.019, R w = 0.022, S = 1.47). It is found that the O(1)(W) site is split into two sites, O(1) and O(11), which are incompletely occupied by fluorine and oxygen anions, respectively, and that the O(3)(V) site contains bivalent oxygen anions. The solid solution studied is close in composition to the liddicoatite mineral species and differs from the latter one by the Li: Al ratio in the Y octahedra and the presence of bivalent oxygen anions in the O(3) site. The tourmaline studied differs from the hypothetical oxyliddicoatite by the population of the O(1)(W) site by fluorine and accommodation of additional oxygen anions in the O(3)(V) site. 相似文献
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Kuz’mina M. A. Rusakov A. V. Frank-Kamenetskaya O. V. Vlasov D. Yu. 《Crystallography Reports》2019,64(1):161-167
Crystallography Reports - The influence of organic and inorganic components of biofilms with microscopic fungi on the phase composition and morphology of precipitating calcium oxalates has been... 相似文献
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A. V. Rusakov O. V. Frank-Kamenetskaya V. V. Gurzhiy M. S. Zelenskaya A. R. Izatulina K. V. Sazanova 《Crystallography Reports》2014,59(3):362-368
The single-crystal structures of four biomimetic weddellites CaC2O4 · (2 + x)H2O with different contents of zeolitic water (x = 0.10–0.24 formula units) produced by the microscopic fungus Aspergillus niger were refined from X-ray diffraction data (R = 0.029–0.038). The effect of zeolitic water content on the structural stability of weddellite was analyzed. The parameter a was shown to increase with increasing x due to the increase in the distance between water molecules along this direction. The water content and structural parameters of the synthesized weddellites are similar to those of weddellites from biofilms and kidney stones. 相似文献
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A. N. Andronov D. V. Daineka G. V. Benemanskaya G. É. Frank-Kamenetskaya 《Physics of the Solid State》1997,39(9):1502-1505
Comparative studies are carried out of the Cs/O/W(110) and Cs/W(110) adsorption systems. The method of threshold photoemission
spectroscopy is used to study the work function and electronic structure in the energy region near the Fermi level as functions
of the sub-monolayer cesium coverage. A significant increase of the saturation cesium coverage is observed on the O/W(110)
surface. A new adsorption-induced surface band is observed in the electronic spectrum of the system Cs/O/W(110) with a binding
energy ∼0.7 eV. For coverages of about one monolayer metallization of the adsorbed layer is observed. It is shown that the
electronic structures of the systems Cs/O/W(110) and Cs/W(110) are similar for low coverages. A difference in the adsorption
properties for these two systems occurs for coverages close to one monolayer, which is explained by the creation of new interaction
centers of the Cs adatoms on the W(110) surface in the presence of oxygen.
Fiz. Tverd. Tela (St. Petersburg) 39, 1683–1686 (September 1997) 相似文献
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I. V. Afanas’ev G. V. Benemanskaya V. S. Vikhnin G. É. Frank-Kamenetskaya N. M. Shmidt 《JETP Letters》2003,77(5):226-229
It is found that Cs adsorption on the n-type GaN(0001) surface generates an unusual change in the electronic properties of the surface and the near-surface space-charge layer, which leads to the appearance of photoelectron emission upon excitation in the transparent region of GaN. It is established that the photoemission is due to the formation of quasimetallic states induced by Cs adsorption in the band-bending region near the surface. The behavior of the photoemission threshold upon excitation by s-polarized light is studied as a function of the Cs coverage. It is found that the minimum value of the threshold corresponds to ~1.4 eV at a concentration of Cs atoms of ~4.5×1014 atom/cm2 in the submonolayer coverage. A new effect is revealed, namely, the appearance of oscillations in the spectral curves of threshold photoemission. A model is proposed for photocurrent oscillations that takes into account the formation of quasimetallic states in the near-surface layer of GaN band bending and the occurrence of interference in the GaN slab upon light irradiation in the transparent region. 相似文献