Structure, dynamics and phase transitions Anharmonic phonons and negative thermal expansion in ScF3 and Ag2O
نویسندگان
چکیده
We report progress towards understanding how phonon anharmonicity contributes to negative thermal expansion (NTE). Some contribution to the NTE is from "quasiharmonic" behavior, where phonon frequencies decrease as a crystal expands. A second "anharmonic" effect from phonon-phonon interactions is sometimes calculated by perturbation theory, but sometimes the anharmonic effects are too large to be treated as perturbations. Both ScF3 and Ag2O, which exhibit large NTE, have some highly anharmonic phonons.
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