Disorder of metal atoms in the structure of quenched high-temperature cubanite, CuFe2S3, Z=4/3.

Abstract

Disorder of the metal atoms in the cubic cubanite, CuFe2S3, Z=4⁄3, obtained by heating orthorhombic cubanite from Ohmine Mine at 300°C for 2 hours and quenched, is investigated by X-rays at room temperature. The cubic cubanite has the sphalerite-type structure with disordered arrangement of the Cu and Fe atoms in the tetrahedral interstices of sulfur atoms of cubic closest packing. The residual electron density around the metal sites in the difference synthesis indicates displacement of some of the metal atoms from the centers of the tetrahedra or anharmonic thermal motion in the tetrahedral sites. For a statistical split atom model, some (∼6%) of metal atoms are displaced toward the four centers of sulfur triangles. The least-squares refinement of anharmonic thermal motion gives the third-order parameter of c123=0.00027(21).