Revision of the Mg(ClO₄)₂·4H₂O crystal structure

Abstract

A revision is presented of the restrained Rietveld analysis of the crystal structure of magnesium perchlorate tetrahydrate, Mg(ClO(4))(2)·4H(2)O, recently published by Robertson & Bish [(2010), Acta Cryst. B 66, 579-584]. The actual symmetry of the material is shown to be C2/m. The corrected structure model is refined by the derivative difference method [Solovyov (2004). J. Appl. Cryst. 37, 743-749], anisotropically for all non-H atoms and isotropically for two independent H atoms without restraints.

Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O

“…2). The crystal structure of strontium perchlorate tetrahydrate is similar to the trihydrate, but different to the magnesium analogue (Robertson & Bish, 2010;Solovyov, 2012) or mercury perchlorate tetrahydrate (Johansson et al, 1966). Two symmetry-related Sr 2+ cations, both coordinated by five water molecules and four monodentate perchlorate tetrahedra, form dimers by sharing two water molecules.…”

Towards “Green” ANFO: Study of Perchlorates and Inorganic Peroxides as Potential Additives

“…This is, however, highly dependent on the utilised additive and organic fuel, indicating the non-straightforward behavior of the additives in the ANFO samples. The difference between the observed trends in the impact and friction sensitivity of perchlorate-supplemented samples may stem from the fact that Ba(ClO 4 ) 2 and Mg(ClO 4 ) 2 crystallise in the hexagonal and monoclinic systems, respectively [32,33]. Such crystal geometry is more prone to tumbling, potentially making those substances act as "lubricants" in the friction sensitivity tests.…”

Accurate unrestrained DDM refinement of crystal structures from highly distorted and low-resolution powder diffraction data

“…Of course, applied properly, the constrained refinement strategy may be useful and even indispensable in cases of complex structures solved from noisy and/or low-resolution data. On the other hand, any restraint imposed excludes the structural parameters from the set of possible validation criteria for accuracy and reliability of structure determination (Solovyov, 2012). Restraints may also induce uncontrolled biases in the unrestrained part of structure geometry, especially when large difference residuals remain in the powder pattern after the refinement.…”