A XAS STUDY OF THE STRUCTURAL-CHANGES UNDERGONE BY AMORPHOUS COPPER SULFIDES WHEN PRECIPITATED FROM SOLUTION

Amorphous copper sulfide precipitates, synthesised from Cu(NO3)(2) sol ution and H2S/Na2S, have been studied by XAS. They all contain Cu(I) a nd age to covellite, but their initial form depends on the concentrati on of the Cu(II) solution. Low concentration solutions give rise to a brown sol, which contains trigonally coordinated Cu(I), while more con centrated solutions produce a black floc, which has a close Cu-Cu inte raction of 2.66 Angstrom similar to that in anilite, Cu7S4 and low cha lcocite, Cu2S.