The structure of lizardite-1T 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) Å], 150 K [a = 5.3260(2), c = 7.2574(6) Å], and 294 K [a = 5.3332(2), c = 7.2718(6) Å] 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 0,0,z positions and is disordered over three symmetry-related positions 0.24 Å 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-1T is proposed: VP.T = Vo[1 + 32.8 × 10-6(T - 294) - 15.5 × 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 by Rietveld powder neutron diffraction. AMERICAN MINERALOGIST, 81(9-10), 1111-1116 [10.2138/am-1996-9-1008].

Hydrogen positions and thermal expansion in lizardite 1T from Elba by Rietveld powder neutron diffraction

GREGORKIEWITZ, M.;MELLINI, M.;VITI, C.
1996-01-01

Abstract

The structure of lizardite-1T 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) Å], 150 K [a = 5.3260(2), c = 7.2574(6) Å], and 294 K [a = 5.3332(2), c = 7.2718(6) Å] 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 0,0,z positions and is disordered over three symmetry-related positions 0.24 Å 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-1T is proposed: VP.T = Vo[1 + 32.8 × 10-6(T - 294) - 15.5 × 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 by Rietveld powder neutron diffraction. 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/11365/10451
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