title: Crystal chemistry of cation-exchanged forms of epistolite-group minerals, Part I. Agand Cu-exchanged lomonosovite and Ag-exchanged murmanite
metadata.name: dc.date.accessioned
metadata.value: 2020-09-09T07:27:06Z
metadata.lang: -
metadata.name: dc.date.available
metadata.value: 2020-09-09T07:27:06Z
metadata.lang: -
metadata.name: dc.date.issued
metadata.value: 2015
metadata.lang: -
metadata.name: dc.identifier.uri
metadata.value: http://hdl.handle.net/11701/19303
metadata.lang: -
metadata.name: dc.description.abstract
metadata.value: The paper presents the first data on the crystal chemistry of the cation-exchanged forms of layered titanosilicates belonging
  to the epistolite group. It was found that these heterophyllosilicates have high exchange capacity and selectivity for cations of
  chalcophile elements (Ag, Cu and Zn) and could be considered as potentially novel raw materials or, more likely, as possible
  prototypes of cation-selective synthetic microporous materials. The crystal structures of Ag- and Cu-exchanged forms of lomonosovite
  and Ag-exchanged form of murmanite were studied by single-crystal X-ray diffraction. The topology of the main structural
  unit, the HOH block, remains unchanged in cation-exchanged forms as compared to the initial lomonosovite Na4Ti4(Si2O7)2O4  
  2Na3PO4 (P-1) and murmanite Na4Ti4(Si2O7)2O4   4H2O (P-1). In Ag-exchanged murmanite, Ag cations occupy two crystallographically
  non-equivalent positions: one in the heteropolyhedral (H) sheet and another one in the octahedral (O) sheet corresponding
  to the positions of Na in initial murmanite. The crystal structure of the Ag-exchanged form of lomonosovite is characterized by an
  increased unit-cell parameter c and doubled parameter b as compared to initial lomonosovite. Ten large-cation sites statistically
  occupied by Ag and Na correspond to the Na sites in the initial lomonosovite: six in the interlayer space, two in the H sheet and two in
  the O sheet. Silver significantly replaces Na in sites in the interlayer space and in the O sheet, whereas sites in the H sheet are less
  affected by the ion exchange. Unit-cell parameter c of the Cu-exchanged form of lomonosovite decreases by 3.58 % as compared to
  the initial lomonosovite whereas a and b remain almost the same. The Cu cations occupy two crystallographically independent
  positions. The Cu(1) site, corresponding to the Na(3) site in the initial lomonosovite, is located in the interlayer space. The lowoccupancy
  Cu(2) site is located on the inversion centre in the O sheet; this site is vacant in the initial lomonosovite. The Cu(2) site is
  surrounded by six O atoms forming an octahedron distorted due to the Jahn-Teller effect.
metadata.lang: en_GB
metadata.name: dc.title
metadata.value: Crystal chemistry of cation-exchanged forms of epistolite-group minerals, Part I. Agand Cu-exchanged lomonosovite and Ag-exchanged murmanite
metadata.lang: en_GB
resources.filename: 1.pdf
resources.url: https://dspace.spbu.ru/bitstream/11701/19303/1/1.pdf
resources.format: Adobe PDF
resources.size: 381,66 kB