Crystal structures of NiSO4·9H2O and NiSO4·8H2O: magnetic properties, stability with respect to morenosite (NiSO4·7H2O), the solid-solution series (MgxNi1−x)SO4·9H2O

Abstract

Since being discovered initially in mixed-cation systems, a method of forming end-member NiSO 4 •9H 2 O and NiSO 4 •8H 2 O has been found. We have obtained powder diffraction data from protonated analogues (with X-rays) and deuterated analogues (using neutrons) of these compounds over a range of temperatures, allowing us to determine their crystal structures-including all H-atoms-and to characterise the transitions on warming from 220 to 278 K; glass → 9-hydrate → 8-hydrate + ice → 7-hydrate + ice → partial melt (7-hydrate + liquid). NiSO 4 •8D 2 O is triclinic, space-group P1 , Z = 2, with unit cell parameters at 150 K,

High-Pressure Behavior of Nickel Sulfate Monohydrate: Isothermal Compressibility, Structural Polymorphism, and Transition Pathway

“…12 The Ni-enrichment in solid phases 5 in the ternary system NiSO 4 −MgSO 4 −H 2 O together with high Ni concentrations in the sulfate-rich soluble fraction of natural meteorite samples 13 emphasize the particular importance of nickel sulfate components, which are also known as the rare terrestrial hydrate minerals morenosite (n = 7), retgersite (n = 6), and dwornikite (n = 1). 14 The monohydrates of divalent cations have received particular attention, since they apparently represent considerably stable solids. They have been observed on Mars and Jovian moons Ganymede and Callisto, preferably as the monohydrated magnesium sulfate mineral kieserite.…”

“…This may include changes of the hydration state, as exemplified by the p -induced dehydration reactions and described for the MgSO 4 · n H 2 O (0 ≤ n ≤ 11) series. − However, it can also involve incongruent melting or polymorphism with associated structural phase transitions . The Ni-enrichment in solid phases in the ternary system NiSO 4 –MgSO 4 –H 2 O together with high Ni concentrations in the sulfate-rich soluble fraction of natural meteorite samples emphasize the particular importance of nickel sulfate components, which are also known as the rare terrestrial hydrate minerals morenosite ( n = 7), retgersite ( n = 6), and dwornikite ( n = 1) …”