English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The new triclinic phase Ca 5 (HAsO 4 ) 2 (AsO 4 ) 2  · 5 H 2 O, polymorph of monoclinic vladimirite, was obtained by dehydration of Ca 5 (HAsO 4 ) 2 (AsO 4 ) 2  · 9H 2 O (ferrarisite) at 60°C. Unit-cell data are:  a  = 8.286(4),  b  = 6.673(3),  c  = 9.743(4) Å,  α  = 86.58(3),  β  = 111.10(3),  γ  = 99.74(3)°;  Z  = 1, space group  P [unk]. The structure was solved by direct methods and least-squares refined to  R  = 0.088, using 1200 observed counter reflections (Mo Kα  radiation). One Ca atom and three water molecules are disordered over centrosymmetrically-related positions. Isostructural (001) layers of Ca and As coordination polyhedra are observed in the structures of both nona- and penta-hydrated phases; however, they differ by a relative shift and sandwich ordered and disordered Ca octahedra, respectively, in the two cases. Dehydration of ferrarisite involves the loss of inter-layer water molecules alternatively from either set of centrosymmetrically-related positions, while layers slide and approach one another. The sandwiched Ca atoms are left attached alternatively to either side of facing layers, and replace their broken coordination bonds by new ones on the side of the shifted layer. This random character of the dehydration reaction is the cause of disorder in the penta-hydrated phase. Crystal-chemical properties of the M 5 (HAsO 4 ) 2 (AsO 4 ) 2  ·  n  H 2 O phases are analyzed.

zeitschrift für kristallographie - crystalline materials

Mechanism of the reaction Ca 5 H 2 (AsO 4 ) 4  · 9 H 2 O (ferrarisite) → Ca 5 H 2 (AsO 4 ) 4  · 5 H 2 O) (dimorph of vladimirite), and structure of the latter phase