First-principles study of (formula presented) cubic phase and average low-(formula presented) rhombohedral phase

Razvan Caracas, Xavier Gonze

Research output: Contribution to journalArticlepeer-review

Abstract

The (formula presented) double perovskite is cubic at high temperature and becomes incommensurately modulated with a rhombohedral (formula presented) average structure at lower temperatures. Both the cubic and rhombohedral average structures are investigated using the local-density approximation within the density-functional theory: We determine the electronic, structural, dielectric, and zone-center dynamical properties. The computed structural parameters are in reasonable agreement with the experiment, with differences up to 2% for the lattice constants. There are two unstable zone-center vibration modes in the cubic phase. The first unstable mode (formula presented) has an antiferrodistortive character, while the second, (formula presented) has a ferrodistortive character. There is no unstable zone-center mode in the rhombohedral phase. We establish the correspondence between the zone-center modes in the two phases.

Original languageEnglish
Pages (from-to)1-7
Number of pages7
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume65
Issue number18
DOIs
Publication statusPublished - 2002
Externally publishedYes

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