Work

The thermal expansion of the clinopyroxene and garnet polymorphs of Na2MgSi5O12 determined by X-ray powder diffraction

Year: 2025

Type: article

Abstract: The temperature dependence of the unit-cell parameters of synthetic Na(Mg0.5Si0.5)Si2O6 clinopyroxene and Na2MgSi5O12 garnet were measured, at atmospheric pressure, using X-ray powder diffraction, from 40 K up to their decomposition temperatures (673 K and 793 K respectively). At 300 K the cell parameters were found to be: (i) a = 9.4073(3) Å, b = 8.6487(3) Å, c = 5.2685(2) Å, β = 108.113(2)°, V = 407.41(3) Å3 and ρ = 3.286 g/cm3, for Na(Mg0.5Si0.5)Si2O6 pyroxene in space-group P2/n with Z = 4 and (ii) a = 11.4155(7) Å, V = 1487.61(5) Å3 and ρ = 3.561 g/cm3 for Na2MgSi5O12 garnet in space-group Ia $$\overline{3}$$ 3 ¯ d with Z = 8. The thermal expansion tensors have been calculated and analysis of the lattice parameters in terms of a Grüneisen-Debye model is used to estimate the Debye temperature and the incompressibility of the two materials at ambient pressure.

Source: Physics and Chemistry of Minerals

DOI: 10.1007/s00269-025-01315-x

Authors: E. K. Tripoliti, A. R. Thomson, D. P. Dobson, P. F. Schofield, I. G. Wood

Institutions: Natural History Museum, University College London

Language: English

Topic: High-pressure geophysics and materials

Subfield: Geophysics

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,490

Funders: Natural Environment Research Council, Science and Technology Facilities Council