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Synchrotron X-ray powder diffraction experiments at high pressure conditions (0.0001–13 GPa) were performed at ESRF (Grenoble-F),
on the beamline ID9, to investigate the bulk elastic properties of natural P2/n-omphacites, with quasi-ideal composition. The monoclinic cell parameters a, b, c and β were determined as a function of pressure, and their compressibility coefficients are 0.00277(7), 0.00313(8), 0.00292(5)
and 0.00116(4) GPa−1, respectively. The third-order Birch-Murnaghan equation of state was used to interpolate the experimental P−V data, obtaining K
0=116.6(±2.5) GPa and K′0=6.03(±0.60). K
0 was also determined by means of the axial and angular compressibilities [122.5(±1.7) GPa], and of the finite Lagrangian strain
theory [121.5(±1.0) GPa]. The discrepancies on K
0 are discussed in the light of a comparison between techniques to determine the bulk modulus of crystalline materials from
static compression diffraction data.
Received: 22 February 2000 / Accepted: 10 July 2000 相似文献
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Azzurra Zucchini Paola Comodi Sabrina Nazzareni Michael Hanfland 《Physics and Chemistry of Minerals》2014,41(10):783-793
Synchrotron single-crystal X-ray diffraction experiments at high-pressure and high-temperature conditions were performed up to 20 GPa and 573.0(2) K on a fully ordered stoichiometric dolomite and a partially disordered stoichiometric dolomite [order parameter, s = 0.26(6)]. The ordered dolomite was found to be stable up to approximately 14 GPa at ambient temperature and up to approximately 17 GPa at T = 573.0(2) K. The P–V data from the ambient temperature experiments were analysed by a second-order Birch–Murnaghan equation-of-state giving K 0 = 92.7(9) GPa for the ordered dolomite and K 0 = 92.5(8) GPa for the disordered dolomite. The high-temperature data, collected for the ordered sample, were fitted by a third-order Birch–Murnaghan equation-of-state resulting in K 0 = 95(6) GPa and K′ = 2.6(7). In order to compare the three experiments results, a third-order Birch–Murnaghan equation-of-state was also calculated for the ambient temperature experiments giving K 0 = 93(3) GPa, K′ = 3.9(6) for the ordered dolomite and K 0 = 92(3) GPa, K′ = 4.0(4) for the disordered dolomite. The derived axial moduli show that dolomite compresses very anisotropically, being the c-axis approximately three times more compressible than the a-axis. The axial compressibility increases as T increases, and the a-axis is the most temperature-influenced axis. On the contrary, axial compressibility is not influenced by disordering. Structural refinements at different pressures show that Ca and Mg octahedra are almost equally compressible in the ordered dolomite with K(CaO6) = 109(4) GPa and K(MgO6) = 103(3) GPa. On the contrary, CaO6 compressibility is reduced and MgO6 compressibility is increased in the disordered crystal structure where K(CaO6) = 139(4) GPa and K(MgO6) = 89(4) GPa. Disordering is found to increase CaO6 and to decrease MgO6 bond strengths, thus making stiffer the Ca octahedron and softer the Mg octahedron. Cation polyhedra are distorted in both ordered and disordered dolomites and they increase in regularity as P increases. Ordered dolomite approaches regularity at approximately 14 GPa. The increase in regularity of octahedra in the disordered dolomite is strongly affected by the very slow regularization of MgO6 with respect to CaO6. The phase transition to the high-pressure polymorph of dolomite (dolomite-II), which is driven by a significant increase in the regularity of both cations polyhedra and mineral crystal structure, occurs in the ordered dolomite at ambient temperature at approximately 14 GPa; whereas no clear evidences of phase transition were observed as regards the disordered crystal structure. 相似文献
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4.
I. Daniel G. Fiquet P. Gillet M. W. Schmidt M. Hanfland 《Physics and Chemistry of Minerals》1999,26(5):406-414
A pressure-volume-temperature data set has been obtained for lawsonite [CaAl2Si2O7(OH)2.H2O], using synchrotron X-ray diffraction and an externally heated diamond anvil cell. Unit-cell volumes were measured to 9.4
GPa and 767 K by angle dispersive X-ray diffraction using imaging plates. Phase changes were not observed within this pressure-temperature
range, and lawsonite compressed almost isotropically at constant temperature. The P-V-T data have been analyzed using a Birch-
Murnaghan equation of state and a linear equation of state expressed as β=–1/V0 (∂V/∂P)
T
. At room temperature, the derived equation of state parameters are: K
0=124.1 (18) GPa K'0 set to 4) and β–1=142.0(24) GPa, respectively. Our results are intermediate between previously reported measurements. The high-temperature
data show that the incompressibility of lawsonite decreases with increasing temperature to ∼500 K and then increases above.
Hence, the second order temperature derivative of the bulk modulus is taken into account in the equation of state; a fit of
the volume data yields K
0=123.9(18) GPa, (∂K/∂T)P=–0.111(3) GPa K–1, (∂2
K/∂T
2)P=0.28(6) 10–3 GPa K–2, α0=3.1(2) 10–5 K–1, assuming K'0=4.
Received: 2 June 1998 / Revised, accepted: 12 Ocotber 1998 相似文献
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Caroline Schmidt Claudia Hanfland Pierre Regnier Philippe Van Cappellen Michael Schl��ter Ulrich Knauthe Ingrid Stimac Walter Geibert 《Geo-Marine Letters》2011,31(4):259-269
Activities of the naturally occurring radium nuclides 228Ra, 226Ra, 224Ra and 223Ra were determined in waters of the open German Bight and adjacent nearshore areas in the North Sea, in order to explore the
potential use of radium isotopes as natural tracers of land–ocean interaction in an environment characterised by extensive
tidal flats, as well as riverine and groundwater influx. Data collected at various tidal phases from the Weser Estuary (228Ra: 46.3 ± 4.6; 226Ra: 17.1 ± 1.1; 224Ra: 26.1 ± 8.2 to 36.5 ± 6.1; 223Ra: 1.8 ± 0.1 to 4.0 ± 0.4), tidal flats near Sahlenburg (228Ra: 39.3 ± 3.8 to 46.0 ± 4.5; 226Ra: 15.5 ± 1.5 to 16.5 ± 1.7; 224Ra: 34.3 ± 2.2 to 85.3 ± 6.3; 223Ra: 3.6 ± 0.5 to 8.0 ± 1.2), freshwater seeps on tidal flats near Sahlenburg (228Ra: 42.1 ± 4.1; 226Ra: 21.3 ± 2.2; 224Ra: 5.1 ± 0.9; 223Ra: 2.6 ± 1.3) and also in permanently inundated parts of the North Sea (228Ra: 23.0 ± 2.3 to 28.2 ± 2.8; 226Ra: 8.2 ± 0.8 to 11.8 ± 1.2; 224Ra: 3.1 ± 1.0 to 10.1 ± 0.9; 223Ra: 0.1 ± 0.02 to 0.9 ± 0.05; units: disintegrations per minute per 100 kg water sample) reveal that, except for the fresh
groundwater, the potential end-members of nearshore water mass mixing have quite similar radium signatures, excluding a simple
discrimination between the sources. However, the decreasing activities of the short-lived 224Ra and 223Ra isotopes recorded towards the island of Helgoland in the central German Bight show a potential to constrain fluxes of land-derived
material to the open North Sea. The largest source for all radium isotopes is generally found on the vast tidal flats and
in the Weser Estuary. Future work could meaningfully combine this so-called radium quartet approach with investigations of
radon activity. Indeed, preliminary data from a tidal flat site with fresh groundwater seepage reveal a 222Rn signal that is clearly lower in seawater. 相似文献
6.
Synthetic Zn-ferrite (ideally ZnFe2O4; mineral name: franklinite) was studied up to 37 GPa, by X-ray powder diffraction at ESRF (Grenoble, France), on the ID9
beamline; high pressure was achieved by means of a DAC. The P-V equation of state of franklinite was investigated using the
Birch-Murnaghan function, and the elastic properties thus inferred [K0 = 166.4(±3.0) GPa K0
′ = 9.3(±0.6) K0
″ = −0.22 GPa−1] are compared with earlier determinations for MgAl-spinel and magnetite. The structural behaviour of Zn-ferrite as a function
of pressure was studied by Rietveld refinements, and interpreted in the light of a phase transition from spinel to either
CaTi2O4- or MnFe2O4-like structure; this transformation occurs above 24 GPa.
Received: 15 March 1999 / Accepted: 22 April 2000 相似文献
7.
Elisabet Verdeny Pere Masqu Jordi Garcia-Orellana Claudia Hanfland J. Kirk Cochran Gillian M. Stewart 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):11
234Th (T1/2=24.1 d) and 210Po (T1/2=138.4 d) are particle reactive radioisotopes that are used as tracers for particle cycling in the upper ocean. Particulate organic carbon (POC) export has frequently been estimated using 234Th/238U disequilibrium. Recent evidence suggests that 210Po/210Pb disequilibrium may be used as an additional tool to examine particle export, given the direct biological uptake of 210Po into cellular material. Differences in these two radioisotope pairs with regard to their half-lives, particle reactivity and scavenging affinity in seawater should provide complementary information to be obtained on the processes occurring in the water column. Here, we review eight different studies that have simultaneously used both approaches to estimate POC export fluxes from the surface ocean. Our aim is to provide a complete “dataset” of all the existing POC flux data derived from the coupled use of both 234Th and 210Po and to evaluate the advantages and limitations of each tracer pair. Our analysis suggests that the simultaneous use of both radiotracers provides more useful comparative data than can be derived from the use of a single tracer alone. The difference in half-lives of 234Th and 210Po enables the study of export production rates over different time scales. In addition, their different biogeochemical behaviour and preferred affinity for specific types of particles leads to the conclusion that 234Th is a better tracer of total mass flux, whereas 210Po tracks POC export more specifically. The synthesis presented here is also intended to provide a basis for planning future sampling strategies and promoting further work in this field to help reveal the more specific application of each tracer under specific water column biogeochemistries. 相似文献
8.
An in situ high pressure powder diffraction study, using high-brilliance synchrotron radiation, on lead feldspar (PbAl2Si2O8) was performed. Two samples, with Q
od=0.68 and 0.76, were loaded in a diamond anvil cell and were compressed up to 11 GPa. Up to P=7.1 GPa the only phase present
is lead feldspar. In the range 7.1–9.4 GPa sudden changes in the position of the reflections suggest the transformation of
lead feldspar to a new phase (probably feldspar-like). The absence of split that would be compatible with triclinic symmetry
rules out the monoclinic-triclinic transition, that was reported for the structurally similar strontium feldspar. At P>9.4 GPa some new extra reflections not indexable in the feldspar cell are present as well. During decompression the lead
feldspar was the only phase present at P<6 GPa. Peak enlargement was observed with pressure, probably preliminary to amorphization. However almost complete amorphization
was observed only after fortuitous shock compression at ∼18 GPa; the crystallinity was recovered at room pressure after decompression.
The bulk modulus for lead feldspar was K=71.0(9) and 67.6(1.2) GPa for the two samples, in the range reported for feldspars.
The cell parameters show a compression pattern which is similar to that observed in anorthite, with Δa/a
0>Δc/c
0>Δb/b
0; comparison with the high temperature behaviour shows that for lead feldspar the strain tensor with pressure is more isotropic
and the deformation along a is less prominent. A turnover in the behaviour of the β angle with pressure suggests a change in the compression behaviour
at P∼2 GPa. Rietveld refinement of the Pb coordinates was performed in a series of spectra with pressure ranging from 0.6 to 6.5
GPa. The combined analysis of cell parameters and Pb coordinates with pressure showed that the compression of the structure
is mainly achieved by an approach of Pb atoms along a
*.
Received: 21 July 1998 / Revised, accepted: 13 October 1998 相似文献
9.
Likhacheva Anna Yu. Rashchenko S. V. Musiyachenko Kira A. Korsakov Andrey V. Collings Ines E. Hanfland Michael 《Mineralogy and Petrology》2019,113(5):613-623
Mineralogy and Petrology - The structural behaviour of maruyamaite (K-dominant tourmaline) X(K0.54Na0.28Ca0.19)Y(Mg1.3Al1.17Fe0.39Ti0.14)Z(Al5Mg)[Si5.95Al0.05O18](BO3)3V,W[O1.69(OH)2.31] from the... 相似文献
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