Analcite (ANL), NaAlSi2O6H2O, is a natural zeolite (or felspathoid). The crystal structure is based on a Secondary Building Unit (SBU) consisting of four-member tetrahedral rings, which are joined to form a complex tetrahedral framework with two different systems of channels: highly distorted 8-rings and regular 6-ring channels. Na and H2O lie into the structural voids. Two H2O and four framework oxygens coordinate the Na-atoms. Elastic and structural behaviour of a natural cubic ANL from Sardinia (Italy) was investigated at HP by in situ single-crystal X-ray diffraction. A first-order phase transition was observed at P = 0.98(7)GPa. Lattice parameters and reflection conditions confirm that the HP-polymorph has a P-1 space group. The experiment is in progress but no further phase-transition has been observed at least up to 6.3 GPa. Fitting the volume data of the cubic polymorph with a BM-EoS we obtain: V0= 2571.2(4)Å3, KT0= 56(3) GPa and K’= 4 (fixed). For the triclinic polymorph: V0= 2618(13)Å3, KT0= 17(1) GPa and K’= 7(1). Tetrahedral tilting produces the relevant structural variations in response of the cubictriclinic phase transition. The SBU distortion gives rise to a change of the 8- and 6-ring channels ellipticity and of the extra-framework content topological configuration: it appear in fact that the coordination number of half of the Na atoms is 7 (2H2O + 5 framework oxygens) instead of 6.

Elastic and structural behaviour of analcite at high pressure / G.D. Gatta, F. Nestola, T. Boffa Ballaran - In: Proceedings 15th Goldschmidt Conference 2005 / The Geochemical Society. - USA : The Geochemical Society, 2005. - pp. A806-A806 (( Intervento presentato al 15. convegno Goldschmidt Conference tenutosi a Moscow, Idaho (USA) nel 2005.

Elastic and structural behaviour of analcite at high pressure

G.D. Gatta
Primo
;
2005

Abstract

Analcite (ANL), NaAlSi2O6H2O, is a natural zeolite (or felspathoid). The crystal structure is based on a Secondary Building Unit (SBU) consisting of four-member tetrahedral rings, which are joined to form a complex tetrahedral framework with two different systems of channels: highly distorted 8-rings and regular 6-ring channels. Na and H2O lie into the structural voids. Two H2O and four framework oxygens coordinate the Na-atoms. Elastic and structural behaviour of a natural cubic ANL from Sardinia (Italy) was investigated at HP by in situ single-crystal X-ray diffraction. A first-order phase transition was observed at P = 0.98(7)GPa. Lattice parameters and reflection conditions confirm that the HP-polymorph has a P-1 space group. The experiment is in progress but no further phase-transition has been observed at least up to 6.3 GPa. Fitting the volume data of the cubic polymorph with a BM-EoS we obtain: V0= 2571.2(4)Å3, KT0= 56(3) GPa and K’= 4 (fixed). For the triclinic polymorph: V0= 2618(13)Å3, KT0= 17(1) GPa and K’= 7(1). Tetrahedral tilting produces the relevant structural variations in response of the cubictriclinic phase transition. The SBU distortion gives rise to a change of the 8- and 6-ring channels ellipticity and of the extra-framework content topological configuration: it appear in fact that the coordination number of half of the Na atoms is 7 (2H2O + 5 framework oxygens) instead of 6.
Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul
2005
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/12920
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