Structure refinement of astrophyllite

Citation
Zs. Ma et al., Structure refinement of astrophyllite, SCI CHINA D, 44(6), 2001, pp. 508-516
Citations number
14
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Earth Sciences
Journal title
SCIENCE IN CHINA SERIES D-EARTH SCIENCES
ISSN journal
1006-9313 → ACNP
Volume
44
Issue
6
Year of publication
2001
Pages
508 - 516
Database
ISI
SICI code
1006-9313(200106)44:6<508:SROA>2.0.ZU;2-B
Abstract
The crystal structure of astrophyllite K2Na(Fe, Mn, Mg, rectangle)(7)[Ti-2( Si4O12)(2)/O-3](OH, F)(4) has been refined. The dimensions of the triclinic unit cell are: a = 0.5359(2) nm, b = 1.1614(4) nm, c = 1.1861(4) nm, alpha = 113.16(2)degrees, beta = 103.04(2)degrees, gamma= 94.56(2)degrees, V = 0 .6495(5) nm(3), Z = 1, space group P1, R = 0.057 for 5308 reflections /F-o/ >3 sigma /F-o/. According to structural and compositional differences the m onoclinic astrophyllite K2NaNa(Fe, Mn)(4)Mg2Ti2[Si4O12](OH)(4)(OH, F)(2) an d astrophyllite should be considered as two different mineral species. Astr ophyllite, monoclinic astrophyllite, bafertisite and lamprophyllite contain heteropolyhedral sheets which topologically are related with Si, O sheets of mica where one or several SiO4 tetrahedra are replaced by TiOn polyhedra . Therefore this heterophyliotitanosilicate series represents a kind of fun ctional substitution in inorganic crystals.