The modulated low-temperature structure of malayaite, CaSnOSiO
DFPT
modulation
optic phonon
satellite reflections
titanite
Journal
Acta crystallographica Section B, Structural science, crystal engineering and materials
ISSN: 2052-5206
Titre abrégé: Acta Crystallogr B Struct Sci Cryst Eng Mater
Pays: England
ID NLM: 101609037
Informations de publication
Date de publication:
01 Jun 2020
01 Jun 2020
Historique:
received:
13
09
2019
accepted:
14
03
2020
entrez:
25
8
2020
pubmed:
25
8
2020
medline:
25
8
2020
Statut:
ppublish
Résumé
The crystal structure of the mineral malayaite has been studied by single-crystal X-ray diffraction at a temperature of 20 K and by calculation of its phonon dispersion using density functional perturbation theory. The X-ray diffraction data show first-order satellite diffraction maxima at positions q = 0.2606 (8)b*, that are absent at room temperature. The computed phonon dispersion indicates unstable modes associated with dynamic displacements of the Ca atoms. The largest-frequency modulus of these phonon instabilities is located close to a wavevector of q = 0.3b*. These results indicate that the malayaite crystal structure is incommensurately modulated by static displacement of the Ca atoms at low temperatures, caused by the softening of an optic phonon with B
Identifiants
pubmed: 32831252
pii: S2052520620003807
doi: 10.1107/S2052520620003807
pmc: PMC7278091
doi:
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
316-321Informations de copyright
open access.
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