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Anharmonicity of forsterite and the thermal pressure of insulators
Author(s) -
Anderson Orson L.
Publication year - 1996
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/96gl02769
Subject(s) - forsterite , anharmonicity , thermodynamics , thermal , isothermal process , materials science , work (physics) , debye model , mineralogy , physics , condensed matter physics , chemistry
A recent paper [ Bouhifd et al., 1996] has given the measured thermal expansivity, α, of forsterite up to 1900 K, which is 2.5 times the Debye temperature, Θ. Using the measured α, Bouhifd et al. [1996] found that the α K T curve (where K T is the isothermal bulk modulus) is parallel to the T axis, showing that (∂(α K T )/∂ T ) P = 0. Using these results, I show that (∂ C v /∂ T ) P > 0 at high T , requiring C v to be anharmonic, is in agreement with other recent work. Further, I show that Bouhifd et al. 's [1996] work requires that all vestiges of anharmonicity be absent in the thermal pressure and the thermal expansivity of forsterite. Thus it is proven that forsterite is a solid that is both anharmonic in C v and quasiharmonic in the thermal pressure in the high‐temperature region.