Structure and stability of Cd2Nb2O7 and Cd2Ta2O7 explored by ab initio calculations
نویسندگان
چکیده
Structural instabilities of Cd2Nb2O7 have been explored by all-electron ab initio calculations in the framework of density-functional theory. The calculated phonon-dispersion curve of the cubic high-temperature phase displays several modes with imaginary frequencies. A distortion according to a T1u mode at the point leads to the energetically most favorable configuration. The resulting structure has been optimized in space-group symmetries Ima2 and I1a1 Cc . The stability of these structures suggests a sequence of phase transitions
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