The Crystal Structures of the Aluminum-Silicate Feldspars

Ribbe, P. H.

doi:10.1007/978-94-011-1106-5_1

Cited by 11 publications

(20 citation statements)

References 48 publications

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“…53 Both Al and Si atoms are 4-fold coordinated by oxygen, forming AlO 4 and SiO 4 tetrahedra. K + ions counterbalance the formal −1 charge of AlO 4 tetrahedra.…”

Section: Results and Discussionmentioning

confidence: 99%

Can Ice-Like Structures Form on Non-Ice-Like Substrates? The Example of the K-feldspar Microcline

et al. 2016

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Feldspar minerals are the most common rock formers in Earth’s crust. As such they play an important role in subjects ranging from geology to climate science. An atomistic understanding of the feldspar structure and its interaction with water is therefore desirable, not least because feldspar has been shown to dominate ice nucleation by mineral dusts in Earth’s atmosphere. The complexity of the ice/feldspar interface arising from the numerous chemical motifs expressed on the surface makes it a challenging system. Here we report a comprehensive study of this challenging system with ab initio density functional theory calculations. We show that the distribution of Al atoms, which is crucial for the dissolution kinetics of tectosilicate minerals, differs significantly between the bulk environment and on the surface. Furthermore, we demonstrate that water does not form ice-like overlayers in the contact layer on the most easily cleaved (001) surface of K-feldspar. We do, however, identify contact layer structures of water that induce ice-like ordering in the second overlayer. This suggests that even substrates without an apparent match with the ice structure may still act as excellent ice nucleating agents.

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“…53 Both Al and Si atoms are 4-fold coordinated by oxygen, forming AlO 4 and SiO 4 tetrahedra. K + ions counterbalance the formal −1 charge of AlO 4 tetrahedra.…”

Section: Results and Discussionmentioning

confidence: 99%

Can Ice-Like Structures Form on Non-Ice-Like Substrates? The Example of the K-feldspar Microcline

et al. 2016

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“…Hence, lead feldspar has a higher transition pressure than could be inferred by considering only the size of the ionic radius. It is known in literature that the significant deviations of lead feldspar from trends of unit-cell parameters vs. volume or ionic radius have been attributed to an effect of the lone-pair (Ribbe 1994). In lead feldspar the relatively high value of the pressure of the I2/c-P2 1 /c transition with respect to alkaline-earth feldspars could be ascribed, besides the specific nature of Pb ++ as a lone-pair bearing cation, also to the degree of Al,Si order.…”

Section: Hp Phase Transition: a Comparison With Alkaline-earth Feldsparsmentioning

confidence: 99%

High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar

Curetti

Benna

Bruno

2015

American Mineralogist

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In situ high-pressure X-ray diffraction study was performed on synthetic lead feldspar with composition PbAl 2 Si 2 O 8 (PbFsp). The crystals were synthesized from the melt and thermally treated at T = 1150 °C for 12 h and at T = 1000 °C for 70 h. At room condition the unit-cell parameters are a = 8.3936(4), b = 13.0498 (7), c = 14.3258(8) Å, b = 115.281(6)°, V = 1418.9(1) Å 3 ; space group: I2/c; Q od = 0.7.A single-crystal of lead feldspar was loaded in an ETH-type diamond-anvil cell and unit-cell parameters were measured at 26 different pressures up to 8.4 GPa at room T. The evolution with P of the unit-cell parameters and volume shows a strong discontinuity between 7.7 and 8.2 GPa indicating a first-order phase transition. The discontinuous character of the transition is especially noticeable in the behavior of the b angle, which decreases from 114.83° to 114.03°, and in the b parameter, which reduces from 12.746 to 12.567 Å.In the P range 0.0001-7.72 GPa, the trend shown by the axial compressibilityis similar to that observed in the previous HP powder diffraction study, performed on lead feldspar using high-brilliance synchrotron radiation up to 7.1 GPa.In the P range 0.0001-4.27 GPa at room T, the P-V data of the I2/c lead feldspar were fitted with a second-order Birch-Murnaghan EoS. The parameters obtained are: V 0 = 1422.2(1) Å 3 and K T0 = 76.4(9) GPa. At P > 4.27 GPa, the volume values deflect from the BM2 curve and show a volume softening, precursor of the reported HP phase transition. A volume softening was recently observed in strontium feldspar (SrFsp) above 4.2 GPa.A second crystal of PbFsp was loaded in the DAC cell and in situ high-pressure X-ray diffraction intensities were measured at P = 0.0001, 2.4, 3.1, 5.4, 6.0, 7.2, 8.4, and 9.7 GPa. The appearance of c and d-type reflections at 8.4 GPa, the analysis of the systematic absence and the structural refinements indicate the HP first-order transformation as an I2/c-P2 1 /c phase transition. Structural results show that the main variations with compression in lead feldspar are in Pb-O bond lengths and in T-O-T bond angles, while T-O distances and O-T-O angles do not change meaningfully, indicating that the Si,Al tetrahedra behave with pressure as a rigid body. Changes observed in the compressional behavior of the structure between 3 and 5 GPa could explain the softening observed at P > 4 GPa in the volume compressibility.The results obtained in the present work allow comparing the pressures of the HP I2/c-P2 1 /c phase transition occurring in lead feldspar with those observed in alkaline-earth feldspars.

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“…The year 1962, a half-century from the discovery of X-ray diffraction, divides the era of "discovery" of the basic architecture and principles of mineral structures from the modern era of investigating the detailed crystal chemistry of minerals. By 1962 there had been 11 full structure refinements of feldspars (Ribbe 1994), made over a period of 30 yr since the original structure determination of sanidine by Taylor (1933). With the larger data sets collected in the 1950s and processed with Hollerith machines and early mainframe computers, the refined structures had a claimed precision in bond lengths of 0.002 Å (e.g., Cole et al 1949) although this uncertainty is clearly underestimated because it is derived directly from the difference Fourier maps (Cochran 1948;Cruickshank 1949aCruickshank , 1949b.…”

Section: The Development Of Diffraction Crystallographymentioning

confidence: 99%

A century of mineral structures: How well do we know them?

Angel

Nestola

2016

American Mineralogist

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This decade marks the centenary of the discovery of X-ray diffraction. The development of mineralogy as a scientific discipline in which the properties of minerals are understood in terms of their atomic-scale structures has paralleled the development of diffraction crystallography. As diffraction crystallography revealed more precise details of mineral structures, more subtle questions about mineral properties could be addressed and a deeper understanding of the relationship between the two could be attained. We review the developments in X-ray single-crystal diffraction crystallography over the last century and show how its power to provide fundamental information about the structures of minerals has evolved with the improvements in data quality and the increased technological capacity to handle the data. We show that modern laboratory X-ray diffraction data are of the quality such that mineralogical results are no longer limited by the data quality, but by the physical validity of the refinement models used to interpret the data.

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The Crystal Structures of the Aluminum-Silicate Feldspars

Cited by 11 publications

References 48 publications

Can Ice-Like Structures Form on Non-Ice-Like Substrates? The Example of the K-feldspar Microcline

Can Ice-Like Structures Form on Non-Ice-Like Substrates? The Example of the K-feldspar Microcline

High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar

A century of mineral structures: How well do we know them?

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The Crystal Structures of the Aluminum-Silicate Feldspars

Cited by 11 publications

References 48 publications

Can Ice-Like Structures Form on Non-Ice-Like Substrates? The Example of the K-feldspar Microcline

Can Ice-Like Structures Form on Non-Ice-Like Substrates? The Example of the K-feldspar Microcline

High-pressure equation of state and phase transition in PbAl2Si2O8feldspar

A century of mineral structures: How well do we know them?

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High-pressure equation of state and phase transition in PbAl₂Si₂O₈feldspar