GLORIA

GEOMAR Library Ocean Research Information Access

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Determination of the centroid or `the best centre' of a coordination polyhedron (1996)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 78-81 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The geometric parameters related to the point in the coordination polyhedron having the minimum variation of distances to the vertices (`the centroid of the coordination polyhedron') are proposed as a measure of polyhedral irregularity or deformation. The numerical method for the determination of the centroid coordinates is described. Knowing these coordinates, the radius of the sphere circumscribed to the coordination polyhedron, the degree of sphericity of coordination, the principal axes of the ellipsoid fitted to the polyhedron and the displacement of the central atom from the centroid are calculated. These quantities are measures for various aspects of irregularity in the coordination polyhedron. The centroid calculation has been applied to the family of ABS2-type sulfides with cations in slightly to highly deformed octahedral coordinations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768195008251
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Nomenclature of inorganic structure types. Report of the International Union of Crystallography Commission on Crystallographic Nomenclature Subcommittee on the Nomenclature of Inorganic Structure Types (1990)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 1-11 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Different degrees of similarity between inorganic crystal structures are defined concisely and examples are presented that illustrate their practical application. A notation giving the coordination of atoms is presented together with some basic rules for developing crystal-chemical formulae and the Bauverband description of inorganic structure types. Typical examples of the nomenclature are: pyrite Fe[6°]{g}[S2(3;1)t], [F(□2l) + F′FeS2Pa\bar 3; spinel Mg[4]AI2[6]O4, ∞3[Mg[4t]lAl2[6o]O4[l,3;12co]], Fm222 + D, T′ MgAI2O4 Fd\bar 3m.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767389008834
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    New Measure of Distortion for Coordination Polyhedra (1998)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 54 (1998), S. 766-773 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A new global measure of distortion for coordination polyhedra is proposed, based on a comparison of the ratios Vs(circumscribed sphere)/Vp(polyhedron) calculated, respectively, for the real and ideal polyhedra of the same number of coordinated atoms which have the same circumscribed sphere. This formula can be simplified to υ (%) = 100[Vi(ideal) − Vr(real)]/Vi, where Vi and Vr are the volumes of the above-defined polyhedra. The global distortion can be combined with other polyhedral characteristics, e.g. with the eccentricity of the central atom in the polyhedron or with the degree of sphericity of the coordination sphere [Balic Zõunic & Makovicky (1996). Acta Cryst. B52, 78–81].Vs/Vp ratios are given for a number of ideal polyhedra, including several types of trigonal coordination prisms, with the aim of facilitating the distortion calculations. The application examples included in the paper are: complex sulfides based on PbS and SnS archetypes, coordination polyhedra of large cations in feldspars, a phase transformation in a monoclinic amphibole and the subdivision of structures isopointal to ilmenite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768198003905
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    The role of Fe2+ and Fe3+ in synthetic Fe-substituted tetrahedrite (1990)
    Springer
    Mineralogy and petrology 43 (1990), S. 73-81 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Die Rolle von Fe2+ und Fe3+ in synthetischen Tetraedriten mit Fe-Substitution Tetraedrite mit einer Zusammensetzung zwischen Cu12Sb4S13 and Cu10Fe2Sb4S13 wurden bei 457 °C und 500 °C aus den Elementen synthetisiert und sorgfdltig mit Mössbauer-Spektroskopie von57Fe untersucht. Zwischen Cu12Sb4S13 and Cu11Fe1Sb4S13 ist Eisen überwiegend dreiwertig. Zwischen Cu11Fe1Sb4S13 and Cu11Fe2Sb4S13 ist Eisen überwiegend zweiwertig und besetzt die tetraedrisch koordinierten M1-Plätze.
    Notes: Summary Tetrahedrites with the composition between Cu12Sb4S13 and Cu10Fe2Sb4S13 were synthesized at 457 °C and 500 °C from the elements and carefully studied by Mössbauer spectroscopy of57Fe. Between Cu12Sb4S13 and Cu11Fe1Sb4S13 iron is predominantly ferric. Between Cu11Fe1Sb4S13 and Cu10Fe2Sb4S13 iron is predominantly ferrous and occupies the tetrahedral M1-sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01164223
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Mineralogical data on a sulphosalt from the Rhodope mountains, Bulgaria (1969)
    Springer
    Mineralogy and petrology 13 (1969), S. 149-156 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Zusammenfassung Bei dem Versuch, die Kristallstruktur von Bonchevit zu bestimmen, stellte sich heraus, daß dieses Mineral—bis dahin PbBi4S7—aus zwei Phasen besteht. Der Hauptanteil wurde eindeutig als Galenobismutit identifiziert. Der Rest wies nach den Gitterkonstanten (a0=13,58±0,02 Å, b0=20,51±0,07 Å, c0=4,09±0,07 Å) auf ein bisher unbekanntes Mineral hin. Die Raumgruppe ist Bbmm. Ein indiziertes Pulverdiagramm und die dazugehörigen d-Werte werden angegeben. Die Emissionsspektralanalyse zeigt Pb und Bi als Hauptkomponenten, Cu und Ag als Nebenkomponenten und Spuren von Zn und Sn. Die Strukturanalyse führte zu der Formel Me5S6, wobei die Me-Atome etwa gleich schwer sind, so daß als chemischo Formel nur Pb3Bi2S6 mit Z=4 in Frage kommt. Strukturell gehört das Mineral in die Gruppe Andorit-Ramdohrit-Fizelyit. Die Verwandtschaft bzw. Identität des Minerals mit anderen Mineralen und synthetischen Verbindungen wird diskutiert.
    Notes: Summary During an attempt to determine the crystal structure of bonchevite, this mineral was found to consist of two phases. Previously it was thought to have the composition PbBi4S7. The main constituent could unambiguously be identified as galenobismutite. For the rest the lattice constants (a0=13.58±0,02 Å, b0=20.51±0,07 Å, c0=4.09±0.07 Å), indicated a new mineral. Space group is Bbmm. An indexed powder diagram (with d-values) is given. The emission spectrographic analysis shows Pb and Bi to be main components, Cu and Ag to be minor components, and traces only of Zn and Sn. The structure analysis has led to the formula Me5S6, with Me-atoms of approximately the same atomic number; therefore, the chemical formula has to be Pb3Bi2S6, with Z=4. In a structural classification the mineral belongs to the andoriteramdohrite-fizelyite-group. The relationships to or the identity with other minerals and synthetic compounds are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088019
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    facet.materialart.
    Unknown
    CRYSTAL STRUCTURES OF SYNTHETIC GOLD-BEARING SULFOSALTS (2012)
    Mineralogical Association of Canada
    Details
    Publication Date: 2012-12-06
    Description: Hydrothermal syntheses in sealed gold tubes produced four distinct sulfosalts of Pb-Bi-Sb-Au, three of them suitable for crystal structure analysis. They have distinct linear-coordinated Au + sites in the structure. The crystal structure of Au 2 Pb 20 (Sb,Bi) 16 S 45 is composed of two types of rods based on SnS archetype, with Pb atoms on the outer surfaces and predominantly Sb and Bi sites in the rod interior. Lead also occurs in the central portions of the larger rod. Linear-coordinated Au and an additional (Pb,Bi) site are interstitial to the rods. The crystal structure of Au 2 Pb 20 (Sb,Bi) 16 S 45 is orthorhombic, space group Cmc 2 1 , with lattice parameters a 4.0260(2), b 75.207(7), and c 27.525(1) Å, and unit cell volume 8334.3 Å 3 . Two structures, Au 2 Pb 12 (Bi,Sb) 18 S 40 and Au 2 Pb 22 (Bi,Sb) 18 S 50 , are homologues N = 2 and N = 4, of a structural series in which slabs of lillianite structure alternate with wavy (100) PbS layers of incrementally increasing thickness (2 and 4 atomic sheets thick, respectively). Linear-coordinated gold (Au-S distance from 2.20 to 2.46 Å) occurs in the former slabs at the boundary to the latter ones. Unit-cell parameters of Au 2 Pb 12 Sb 18 S 40 are as follows: a 4.11(1), b 44.50(1), and c 20.56(1) Å (film data), cell volume 3760.3 Å 3 , and space group Cmc 2 1 . Those of Au 2 Pb 22 Sb 18 S 50 are a 4.0876(4), b 55.1514(48), and c 20.4219(11) Å, cell volume 4604.29 Å 3 , and the same space group. The increment of the b parameter reflects the change in the homologue number N.
    Print ISSN: 0008-4476
    Topics: Geosciences
    Published by Mineralogical Association of Canada
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    The crystal structure of ramdohrite, Pb5.9Fe0.1Mn0.1In0.1Cd0.2Ag2.8Sb10.8S24: A new refinement (2013)
    Mineralogical Society of America
    Details
    Publication Date: 2013-03-30
    Description: The crystal structure of ramdohrite, Pb 5.9 Fe 0.1 Mn 0.1 In 0.1 Cd 0.2 Ag 2.8 Sb 10.8 S 24 , from the Chocaya mine, Potosí, Bolivia, determined by Makovicky and Mumme from film data in 1983, was refined from single-crystal diffractometer data to the R value 0.060, based on 5230 reflections [ I 〉 2( I )] from a twinned crystal. Lattice parameters are a = 8.7348(3), b = 13.0543(4), c = 19.3117(6) Å, and β = 90.179(2)°, space group P 2 1 / n . Two bicapped trigonal prismatic sites of lead bridge and unite adjacent (311) PbS slabs. These slabs contain five distinct coordination pyramids of Sb with trapezoidal cross sections, a mixed and disordered Sb-Ag-Cd-(Pb) site, refined as 0.39 Sb + 0.61 Ag, a pure Ag site with a very open, irregular tetrahedral coordination, and an octahedral site occupied by Pb. The (311) PbS slabs contain large lone electron pair micelles formed by four distinct antimony sites in alternation with small such micelles formed by a single Sb site. The geometric arrangement of these slabs is not based on crankshaft chains of short, strong Me-S bonds but on a chess-board arrangement of (predominantly) Sb pairs that share two common S atoms via short bonds. Relationships to, and differenced from, fizelyite and uchucchacuaite are described and discussed.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    Quadratite, AgCdAsS3: Chemical composition, crystal structure, and OD character (2012)
    Mineralogical Society of America
    Details
    Publication Date: 2012-12-22
    Description: A re-investigation of the crystal structure of quadratite, ideally AgCdAsS 3 , was undertaken using a single crystal from the type locality, Lengenbach, Binntal, Switzerland. The average of five electron microprobe analyses led to the empirical formula (Ag 0.994 Cd 0.738 Pb 0.231 Cu 0.006 Tl 0.005 Mn 0.003 Fe 0.004 Zn 0.002 Cr 0.001 ) =1.984 (As 0.955 Sb 0.003 ) =0.958 S 3.058 . A single-crystal structure refinement ( R 1 = 4.84% for 558 observed reflections) shows that quadratite crystallizes in the space group P 4 3 22 and exhibits an atomic arrangement similar to that of the recently approved new mineral manganoquadratite, AgMnAsS 3 . Like manganoquadratite, quadratite adopts a galena-derivative framework, with metal atoms occupying all the available octahedral interstices, although only M1 and M2 cations, occupied mainly by Cd, adopt a fairly regular octahedral coordination; the M3 cation, occupied by Ag, is located outside the center cavity in a square-pyramidal coordination, whereas Pb at the split position M3' coordinates six S atoms. Arsenic also adopts a 3 + 3 asymmetrical coordination, thus forming the AsS 3 pyramidal groups that typically occur in sulfosalts. The structure can be also described as a stacking of BAB slabs [A: (Cd,Ag)CdS 2 atomic plane; B: (Ag,Pb)AsS 2 atomic plane] along [001]. The rectangular unit cell of these slabs is oriented diagonally to the a axes of quadratite and consecutive slabs are related via interlayer twofold rotation operations parallel either to [100] or to [010]. This ambiguity leads to an OD structure with various possible stacking sequences, from which the tetragonal space group P 4 3 22 was observed.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 9
    facet.materialart.
    Unknown
    THE Pd-Ni-Fe-s Phase System At 550 and 400 {degrees}C (2017)
    Mineralogical Association of Canada
    Details
    Publication Date: 2017-02-03
    Description: The condensed Pd–Ni–Fe–S phase system was studied at 550 and 400 °C by synthesis in evacuated silica glass tubes and a combination of textural and electron microprobe studies. The monosulfide Fe 1– x S–Ni 1– x S solid solution persists at both temperatures. Maximum solubility of Pd, exhibited at elevated x values in the mss formula, is 0.7 at.% at 550 °C and up to 0.1 at.% at 400 °C. The field of sulfide melt is reduced to a narrow Ni-Pd rich stripe at 550 °C and is absent at 400 °C. Sulfur contents of the melt are limited to the interval 30–40 at.% S at 550 °C, i.e ., it is metal-rich. Retreat of the melt field at 550 °C results in a plethora of phase associations in its place. Compositional fields of alloys associated with melt and of those associated with ~(Ni,Fe) 3± x S 2 extend to high Pd contents. Several sulfur-poor associations contain alloys with only low nickel contents, close in composition to Pd 3 Fe. Shrinkage of the ~(Ni,Fe) 3± x S 2 phase field (the β 1 -β 2 pair of Kitakaze et al . 2011 ) and the appearance of pentlandite represent the most important developments in the phase system between 725 and 400 °C. The ~(Ni,Fe) 3± x S 2 phase dissolves up to 2 at.% Pd at 550 °C. Pentlandite associated with Pd-rich phases dissolves up to 4 at.% Pd at 550 °C, and 5.4 at.% Pd at 400 °C. The latter value represents almost 92% Pd occupancy of the octahedral site. At 550 °C, Pd-rich pentlandite coexists with sulfide melt which contains between 17 and 47 at.% Pd. The rare occurrences of such Pd-rich pentlandite in nature could indicate the presence of Pd-rich residual melts. Other cases of Pd-rich pentlandite associate with Pd-rich alloy or phases like PdS and Pd 2.2 S. In the association with mss , Pd is concentrated in the sulfide melt, especially at a low temperature. At low temperatures or high S fugacities, nickel prefers mss but pentlandite and ~(Ni,Fe) 3± x S 2 complicate this simple scheme. For mineral associations with elevated sulfur fugacities, pyrrhotite ( mss ) appears to be a principal solid-state collector of Pd at high temperatures, with its gradual release on cooling, making it available for subsequent reactions. At low sulfur fugacities Pd concentrates in its Fe-Ni alloys. Because of the inverse relationship between Ni solubility in PdS and the temperature of formation, the composition of natural vysotskite (and Pd-rich braggite) may serve as a temperature indicator.
    Print ISSN: 0008-4476
    Topics: Geosciences
    Published by Mineralogical Association of Canada
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    Exploratory studies of the Cu-Pd-Se system at 650 {degrees}C, 550 {degrees}C, 400 {degrees}C, and 300 {degrees}C (2017)
    Schweizerbart
    Details
    Publication Date: 2017-09-28
    Description: The condensed-phase system Cu–Pd–Se was investigated by means of dry syntheses from elements in evacuated silica glass tubes at 650 °C, 550 °C, 400 °C, and 300 °C. Synthetized phases were analysed by electron microprobe and textural studies in polished sections. At 650 °C an extensive selenide liquid field covers central portions of the system, coexisting with a limited choice of Pd selenides, Cu 2– x Se, alloys, and a (Cu,Pd)Se 2 solid solution. The selenide melt recedes to the Pd side of the system at 550 °C and its remnants persist at 400 °C. At the lower temperature, the gamut of Pd selenides becomes richer, and especially Pd 4 Se and Pd 17 Se 15 display significant solubility of Cu. The composition range of (Cu,Pd)Se 2 broadens and moves towards Cu-richer compositions as temperature decreases; CuSe and CuSe 2 appear at 300 °C. The synthetic analogue of jaguéite, Cu 2 Pd 3 Se 4 , is present at 400 °C and 300 °C, at Se concentrations above the Cu 2– x Se–Pd 17 Se 15 line. At all examined temperatures, the individualized CuPd alloy dissolves Se, up to ~5 at% at low temperatures.
    Print ISSN: 0935-1221
    Electronic ISSN: 1617-4011
    Topics: Geosciences
    Published by Schweizerbart
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...