The crystal structure of parthéite

Abstract

Partheite is a zeolite-like mineral of composition Ca 2 Al4Si 4 Oi5(OH) 2 ·4Η 2 0. It crystallizes with monoclinic symmetry, space group C2/c, α = 21.555(3), b = 8.761(1), c = 9.304(2) Ä, 0 = 91.55(2), Z=4, £>", = 2.39 g/cm 3 , D x = 2.41 g/cm 3 . Its structure consists of Γ-centered T0 4 tetrahedra (Γ= Al,Si) which are connected via corners to a 3-dimensional framework. Due to the presence of hydroxyl groups the framework is interrupted at every second A10 4 tetrahedron. Water molecules and Ca atoms are situated in large channels which cross the structure parallel to c. The channels are delimited by zig-zag chains of nearly flat 10-membered rings. The framework also contains 8-membered rings and two types of 4-and 6-membered rings of oxygen tetrahedra.

Flexibility versus rigidity: what determines the stability of zeolite frameworks? A case study

“…The residual Q 3 silicon atoms could be due to defect sites already present in -COK-14(H1) before heating, or disruption of some bonds in the layers upon heating resulting in additional silanol groups, or due to incomplete condensation of the systematic silanol groups. Exposure to water at 333 K to form the interrupted -COK-14(H2) increases the Q 3 silicon atom concentration at the expense of Q 4 , reaching a value of 16%, slightly exceeding the value of 13% for -COK-14(H1). The 29 Si MAS NMR spectrum of -COK-14(H2) can be tted as a linear combination of 77% -COK-14(H1), 21% COK-14(C1) and 2% Q 3 silanols, as shown in Fig.…”

“…While these broken links are oen statistically distributed, an interruption in fourconnected frameworks can also occur periodically. Framework type codes assigned to such periodically interrupted frameworks are indicated by a leading dash, and are encountered in both naturally occurring zeolites (-CHI, 1 -LIT, 2 -PAR, 3 -RON, 4 -WEN 5 and synthetic materials (-CLO, 6,7 -ITV, 8 -IRY, 9 -SRV 10 ). The The outstanding stability of zeolites is one of the reasons for their success as porous materials in industry.…”

Investigation of Si Atom Migration in the Framework of MSE-Type Zeolite YNU-2

“…In contrast to the framework of MFI zeolite, there are seven zeolite topologies with an orderly distribution of hydroxyl group in their framework: -CHI , -CLO , -LIT , -PAR , -RON , -SVR , and -WEN . − Although these structures have open-framework geometry, the hydroxyl groups of some T-sites are isolated in the framework except in the case of -LIT and -SVR zeolites. In -LIT , two silanol groups are located close together with an interatomic distance of ca.…”

Roggianite: revised chemical formula and zeolitic properties

“…Therefore, roggianite is the first and up to now the only zeolite with many tetrahedral sites occupied by Be atoms; in particular, the structural data (Galli, 1980) suggest that Be atoms are present only in A1 tetrahedra. Among the zeolitic minerals, the interrupted framework for the (OH) groups is known in partheite (Engel and Yvon, 1984); unlike partheite, roggianite is characterized also by the presence of extra-framework (OH) groups, which is unique in this group of minerals.…”