A solid solution series of atacamite type Ni2xMg2−2xCl(OH)3

•First synthesis of solid solution series between main and transition metal chloride.•Ni2+ prefers to occupy Jahn–Teller-like distorted octahedral holes.•Substitution of Ni2+ by Mg2+ results in systematic Raman and IR band shifts.•α-Polymorphs M2Cl(OH)3 with M=Mg2+, Ni2+, … as described in literature do not exist.

For the first time a complete solid solution series Ni2xMg2−2xCl(OH)3 of an atacamite type alkaline main group metal chloride, Mg2Cl(OH)3, and a transition group metal chloride, Ni2Cl(OH)3, was prepared and characterized by chemical and thermal analysis as well as by Raman and IR spectroscopy, and high resolution laboratory X-ray powder diffraction. All members of the solid solution series crystallize in space group Pnam (62). The main building units of these crystal structures are distorted, edge-linked Ni/MgO4Cl2 and Ni/MgO5Cl octahedra. The distribution of Ni2+- and Mg2+-ions among these two metal-sites within the solid solution series is discussed in detail. The crystallization of the solid solution phases occurs via an intermediate solid solution series, (Ni/Mg)Cl2x(OH)2−2x, with variable Cl: OH ratio up to the 1:3 ratio according to the formula Ni2xMg2−2x Cl(OH)3. For one isolated intermediate solid solution member, Ni0.70Mg0.30Cl0.58(OH)1.42, the formation and crystal structure is presented as well.

Graphical abstractFor the first time a complete solid solution series, Ni2xMg2−2x Cl(OH)3, was synthesized and characterized. Structure solution by revealed that Ni2+ prefers to occupy the Jahn–Teller-like distorted hole, out of two available cation sites. Substitution of Ni2+ by Mg2+ in atacamite type Ni2Cl(OH)3 results in systematic band shifts in Raman and IR spectra as well as in systematic changes in thermal properties. The α-polymorphs M2Cl(OH)3 with M=Mg2+, Ni2+ and other divalent transition metal ions, as described in literature, were identified as separate compounds.Figure optionsDownload full-size imageDownload as PowerPoint slide