New thermoelastic parameters of natural C2/c omphacite

作者：Pandolfo Francesco^*; Nestola Fabrizio; Camara Fernando; Domeneghetti M Chiara

来源：Physics and Chemistry of Minerals, 2012, 39(4): 295-304.

DOI：10.1007/s00269-012-0484-1

• Omphacite
• High pressure
• High temperature
• Single crystal
• X-ray diffraction

The compressibility at room temperature and the thermal expansion at room pressure of two disordered crystals (space group C2/c) obtained by annealing a natural omphacite sample (space group P2/n) of composition close to Jd(56)Di(44) and Jd(55)Di(45), respectively, have been studied by single-crystal X-ray diffraction. Using a Birch-Murnaghan equation of state truncated at the third order [BM3-EoS], we have obtained the following coefficients: V (0) = 421.04(7) a%26quot;%26lt;%26lt;(3), K (T0) = 119(2) GPa, K%26apos; = 5.7(6). A parameterized form of the BM3 EoS was used to determine the axial moduli of a, b and c. The anisotropy scheme is beta (c) a parts per thousand currency sign beta (a) a parts per thousand currency sign beta (b) , with an anisotropy ratio 1.05:1.00:1.07. A fitting of the lattice variation as a function of temperature, allowing for linear dependency of the thermal expansion coefficient on the temperature, yielded alpha(V(1bar,303K)) = 2.64(2) x 10(-5) K-1 and an axial thermal expansion anisotropy of alpha (b) a parts per thousand %26lt;%26lt; alpha (a) %26gt; alpha (c) . Comparison of our results with available data on compressibility and thermal expansion shows that while a reasonable ideal behaviour can be proposed for the compressibility of clinopyroxenes in the jadeite-diopside binary join [K (T0) as a function of Jd molar %: K (T0) = 106(1) GPa + 0.28(2) x Jd((mol%))], the available data have not sufficient quality to extract the behaviour of thermal expansion for the same binary join in terms of composition.

• 出版日期2012-4