Using ab initio plane-wave pseudo-potential density functional theory method, the elastic constants and band structures of stishovite were calculated. The calculated elastic constants under ambient conditions agree well with previous experimental and theoretical data. C 13 , C 33 , C 44 , and C 66 increase nearly linearly with pressure while C 11 and C 12 show irregularly changes with pressure over 20 GPa. The shear modulus (C 11 -C 12 )/2 was observed to decrease drastically between 40 GPa and

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... 50 GPa, indicating acoustic mode softening in consistency with the phase transition to CaCl 2 -type structure around 50 GPa. The calculated band structures show no obvious difference at 0 and 80 GPa, being consistent with the high incompressibility of stishovite. With a quasi-harmonic Debye model, thermodynamic properties of stishovite were also calculated and the results are in good agreement with available experimental data.