Cation Distribution in Mixed Formates. I. Change in Lattice Constants and in Infrared Spectra with the Chemical Constitution of (Cu,MII)(HCOO)2·2H2O

Abstract

Abstract Mixed crystals of formates, with the general formula of (Cu,MII)(HCOO)2·2H2O, were found to show non-uniform changes in lattice constants with the change in the chemical constitution. The reason for this unusual change was sought in relation to a possible non-uniform distribution of the cations over the two non-equivalent sites for metal ions. A simple model based merely on the difference in the radii of metallic ions did not agree with the results of IR measurements nor with those of an ESR study by Wagner et al. Another model, incorporating the change in the direction of the longest axis of the octahedron coordinating to the Cu2+ ion at the Ml-site, as suggested from the results of a related work (Part II), was found not only to explain the changes in lattice constants, but also to conform with other evidences; it seems to be an essentially correct interpretation.