Synthesis and crystal structure of Co ₂ (OH) ₂ CO ₃ by Rietveld method

Abstract

A new cobalt hydroxide carbonate Co 2 (OH) 2 CO 3 was successfully synthesized by a hydrothermal method. The compound is isomorphous with malachite [Cu 2 (OH) 2 CO 3 ] and crystallizes in a monoclinic system [space group P 2 1 / a (No. 14); a =9.448(5) Å, b =12.186(9) Å, c =3.188(4) Å, β =98.593°, V =367.143(9) Å 3 , Z =4, and D c =3.786(9) g/cm 3 ]. Crystal structure of Co 2 (OH) 2 CO 3 was refined by the Rietveld method with R P =4.3%, R W P =5.7%, R e x p =5.1%, R B =1.74%, and S =1.117 on the basis of the X-ray powder diffraction data. The crystal structure of Co 2 (OH) 2 CO 3 obtained by the Rietveld refinement shows that all species Co 2+ , CO 3 2− , and OH − ions occupy C 1 site symmetry. Two crystallographically different Co 2+ and OH − ions and one type CO 3 2− ion exist in the lattice. Co(1) is coordinated to two oxygen atoms from CO 3 2− ions and two OH − ions; Co(2) is coordinated to two oxygen atoms from CO 3 2− ions and four OH − ions, thus forming a distorted octahedron with (4+2) coordination.