• journal_title：Mineralogical Magazine
• Contributor：M. Wierzbicka-Wieczorek ; U. Kolitsch ; L. Nasdala ; E. Tillmanns
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2010-
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2010.074.6.979
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：74
• issue：6
• firstpage：979
• section：Articles

The new, non-centrosymmetric chain silicate, K_2.9Rb_0.1ErSi₃O₉, was prepared by a high-temperature flux-growth technique, and its crystal structure was determined from single-crystal X-ray intensity data (Mo-m>Km>α, 293 K) in space m>Pm>1, with m>am> = 6.672(1), m>bm> = 6.719(1), m>cm> = 6.725(1) Å, α = 108.87(3), β = 106.72(3), γ = 107.61(3)°, m>Vm> = 245.82(6) ų, m>Zm> = 1, m>Rm>(m>Fm>) = 2.81%. The compound represents a novel structure type. K_2.9Rb_0.1ErSi₃O₉ is characterized by a mixed octahedral-tetrahedral framework, in which each corner of the isolated ErO₆ octahedron (<Er–O> = 2.26 Å) is linked toinfinite [Si₃O₉] chains extending approximately along [111]. This connectivity results in a microporous character with two different, narrow channels that extend parallel to [111] and [100] and host K⁺ cations. The atomic arrangement is strongly pseudorhombohedral. A single-crystal Raman spectrum of K_2.9Rb_0.1ErSi₃O₉ is in agreement with the low space-group symmetry. Relations to minerals and synthetic compounds based on [Si₃O₉] chains are discussed, revealing that the geometry of the chain in K_2.9Rb_0.1ErSi₃O₉ is similar tothat in pectolite, NaCa₂[HSi₃O₉].