TY - JOUR

T1 - Structure evolution of hydroxyapophyllite-(K) under high pressure

AU - Seryotkin, Yurii V.

N1 - This study is supported by the Russian Science Foundation (grant # 22-27-00235). The chemical analyses were carried out at the Analytical Center for Multi-Elemental and Isotope Research (Sobolev Institute of Geology and Mineralogy, Novosibirsk, Russia). X-ray experiments were done using the equipment of Research and Education Centre “Molecular Design and Ecologically Safe Technologies” at NSU.

PY - 2024/3

Y1 - 2024/3

N2 - The high-pressure structural evolution of a natural hydroxyapophyllite-(K) K0.96 Ca4.01[Al0.01Si7.99O20]((OH)0.95F0.05)·(H2O)8.14, Z = 2, a = 8.9699(1), c = 15.8934(3) Å, space group P4/mnc, from the Hatrurim Basin, Negev Desert, compressed in penetrating (ethanol:water 8:1 mixture) medium up to 5 GPa, was studied by single-crystal X-ray diffraction with a diamond anvil cell. The results clearly demonstrate the absence of pressure-induced hydration in the structure. Within 3 GPa, the compression mechanism is similar to that known in fluorapophyllite-(K). The compression in the plane of silicate layer proceeds via the relative rotation of the four-membered rings. The compression along the c-axis proceeds through the shortening of the inter-layer distance, whereas the thickness of silicate layer remains almost unchanged. As a result, the pressure-induced changes in the unit-cell metrics are similar to those for fluorapophyllite-(K). At about 3 GPa, hydroxyapophyllite-(K) undergoes a phase transition with the symmetry lowering to orthorhombic (space group Pnnm). The symmetry of the high-pressure phase allows deformation of the four-membered rings of the silicate layer, which is impossible within tetragonal symmetry. In this case, the structure is compressed much more along the a-axis than along the b-axis. As a result, the orthorhombic phase of hydroxyapophyllite-(K) is more compressible compared to fluorapophyllite-(K).

AB - The high-pressure structural evolution of a natural hydroxyapophyllite-(K) K0.96 Ca4.01[Al0.01Si7.99O20]((OH)0.95F0.05)·(H2O)8.14, Z = 2, a = 8.9699(1), c = 15.8934(3) Å, space group P4/mnc, from the Hatrurim Basin, Negev Desert, compressed in penetrating (ethanol:water 8:1 mixture) medium up to 5 GPa, was studied by single-crystal X-ray diffraction with a diamond anvil cell. The results clearly demonstrate the absence of pressure-induced hydration in the structure. Within 3 GPa, the compression mechanism is similar to that known in fluorapophyllite-(K). The compression in the plane of silicate layer proceeds via the relative rotation of the four-membered rings. The compression along the c-axis proceeds through the shortening of the inter-layer distance, whereas the thickness of silicate layer remains almost unchanged. As a result, the pressure-induced changes in the unit-cell metrics are similar to those for fluorapophyllite-(K). At about 3 GPa, hydroxyapophyllite-(K) undergoes a phase transition with the symmetry lowering to orthorhombic (space group Pnnm). The symmetry of the high-pressure phase allows deformation of the four-membered rings of the silicate layer, which is impossible within tetragonal symmetry. In this case, the structure is compressed much more along the a-axis than along the b-axis. As a result, the orthorhombic phase of hydroxyapophyllite-(K) is more compressible compared to fluorapophyllite-(K).

KW - Apophyllite group

KW - Fluorapophyllite-(K)

KW - High pressure

KW - Hydroxyapophyllite-(K)

KW - Structural evolution

KW - X-ray diffraction

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85183445506&origin=inward&txGid=1628f9de8e13f6f6651aa8953bcbaa56

UR - https://www.mendeley.com/catalogue/6f7af698-ed74-32f5-9670-04bc9083447d/

U2 - 10.1007/s00269-023-01265-2

DO - 10.1007/s00269-023-01265-2

M3 - Article

VL - 51

JO - Physics and Chemistry of Minerals

JF - Physics and Chemistry of Minerals

SN - 0342-1791

IS - 1

M1 - 3

ER -