The structure of lizardite-l T from Monte Fico, Elba, was refined in space group P31m using neutron diffraction data, measured at 8, 150, and 294 K, and full-profile Rietveld refinement techniques. The lattice parameters at 8 K [a = 5.3267(2), c = 7.2539(6) A], 150 K [a = 5.3260(2), c = 7.2574(6) A], and 294 K [a = 5.3332(2), c = 7.2718(6) A] show nonlinear expansion, with nearly all volume change above 150 K. H positions were precisely refined at 8 K. The inner H4 atom deviates from the idealized O,O,zpositions and is disordered over three symmetry-related positions 0.24 A away from the ternary axis. The outer H3 atom location is consistent with the previous single-crystal X-ray structure refinement. On the basis of the present thermal expansion data and previous compressibility measurements, the following equation of state for lizardite-I T is proposed: Vp,T = Vo[1 + 32.8 x 10-6(T - 294) - 15.5 x 10⁻⁴(P - 0.001)]. Accordingly, the constant volume condition requires geothermal gradients on the order of 15 °C/km.

Gregorkiewitz, M., Lebech, B., Mellini, M., Viti, C. (1996). Hydrogen positions and thermal expansion in lizardite-1T from Elba: A low-temperature study using Rietveld refinement of neutron diffraction data. AMERICAN MINERALOGIST, 81(9-10), 1111-1116 [10.2138/am-1996-9-1008].

Hydrogen positions and thermal expansion in lizardite-1T from Elba: A low-temperature study using Rietveld refinement of neutron diffraction data

Gregorkiewitz, M.;Mellini, M.;Viti, C.
1996-01-01

Abstract

The structure of lizardite-l T from Monte Fico, Elba, was refined in space group P31m using neutron diffraction data, measured at 8, 150, and 294 K, and full-profile Rietveld refinement techniques. The lattice parameters at 8 K [a = 5.3267(2), c = 7.2539(6) A], 150 K [a = 5.3260(2), c = 7.2574(6) A], and 294 K [a = 5.3332(2), c = 7.2718(6) A] show nonlinear expansion, with nearly all volume change above 150 K. H positions were precisely refined at 8 K. The inner H4 atom deviates from the idealized O,O,zpositions and is disordered over three symmetry-related positions 0.24 A away from the ternary axis. The outer H3 atom location is consistent with the previous single-crystal X-ray structure refinement. On the basis of the present thermal expansion data and previous compressibility measurements, the following equation of state for lizardite-I T is proposed: Vp,T = Vo[1 + 32.8 x 10-6(T - 294) - 15.5 x 10⁻⁴(P - 0.001)]. Accordingly, the constant volume condition requires geothermal gradients on the order of 15 °C/km.
Gregorkiewitz, M., Lebech, B., Mellini, M., Viti, C. (1996). Hydrogen positions and thermal expansion in lizardite-1T from Elba: A low-temperature study using Rietveld refinement of neutron diffraction data. AMERICAN MINERALOGIST, 81(9-10), 1111-1116 [10.2138/am-1996-9-1008].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11365/21183
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