Incommmensurately modulated crystal structure of flamite

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Marco E. Ciriotti
Messaggi: 26368
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Incommmensurately modulated crystal structure of flamite

Messaggio da Marco E. Ciriotti » mar 22 ott, 2019 11:05

Prossima pubblicazione.

Referenza:
▪ Rashchenko, S.V., Seryotkin, Y.V., Sokol, E.V., Kokh, S.N. (2019): Incommmensurately modulated crystal structure of flamite – natural analogue of alpha-Ca2SiO4. Acta Crystallographica, B75, (in press).

Synopsis:
Incommensurately modulated crystal structure of flamite – natural analogue of high-temperature alpha-modification of Ca2SiO4 is described.

NdR: polimorfo di alta temperatura (1425-2150°C) di calcio-olivina, larnite, breidigite.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 26368
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Incommmensurately modulated crystal structure of flamite

Messaggio da Marco E. Ciriotti » mar 03 dic, 2019 15:18

Pubblicazione effettuata.

Referenza:
▪ Rashchenko, S.V., Seryotkin, Y.V., Sokol, E.V., Kokh, S.N. (2019): Incommmensurately modulated crystal structure of flamite – natural analogue of alpha-Ca2SiO4. Acta Crystallographica, B75, 1137-1143.

Abstract:
Crystal structures of unquenchable high‐temperature polymorphs of Ca2SiO4, important in cement chemistry, have eluded single‐crystal X‐ray analysis. However, the problem may be addressed by studying chemically stabilized Ca2SiO4 polymorphs at ambient temperature. Here an incommensurately modulated crystal structure of flamite [Pnma(0β0)00s, q = 0.2728 (2)b*, a = 6.8588 (2) Å, b = 5.4301 (2) Å, c = 9.4052 (3) Å] is described. It is a mineral analogue of orthorhombic \alpha _{\rm H}^{\prime}‐Ca2SiO4 (stable between 1160 and 1425°C), naturally stabilized by substitution with phosphorus. The incommensurate modulation results from wave‐like displacement of cation sites accompanied by tilting of (Si,P)O4 tetrahedra and variation of the Na/(Ca + Na + K) ratio along the modulation period. The studied sample from Hatrurim Basin (Negev Desert, Israel) with composition (Ca1.75K0.12Na0.12)1.99(Si0.74P0.26)1.00O4 also demonstrates pseudomerohedral cyclic twinning around the a axis, which results from pseudohexagonal topology of the crystal structure and complicates the indexing of X‐ray diffraction data.
Marco E. Ciriotti

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