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environmental, earth and planetary science
The temperature dependence of EXAFS Debye–Waller factors in CaTiO3, SrTiO3 and CaGeO3 perovskite was investigated with the cumulant expansion method. The CaGeO3 perovskite as an analogue of the Earth's lower-mantle mineral was synthesized in a cubic anvil type apparatus under 10 GPa 1250 K. The Ca, Ti and Ge K-edge EXAFS spectra were measured in transmission mode at temperature up to 1100 K. The effective pair potentials, V(u) = αu2/2 + βu3/3!, were evaluated and the Grüneisen parameter were calculated. The potential coefficients α and β for Ti—O bond in CaTiO3 are 6.9 eV Å−2 and −38 eV Å−3, respectively. Those for Ge—O bond in CaGeO3 are 9.8 eV Å−2 and −36 eV Å−3, respectively.