UNDERSTANDING THE HABIT MODIFICATION OF AMMONIUM DIHYDROGEN PHOSPHATEBY CHROMIUM IONS USING A DOPANT-INDUCED CHARGE COMPENSATION MODEL

The habit modification of ammonium dihydrogen phosphate when grown fro m an aqueous solution containing CrCl3 . 6H(2)O has been studied using UV-vis spectroscopy and X-ray absorption spectroscopy. Upon incorpora tion into the crystal lattice, the cationic Cr complex manifests a com pression of the bonding distance to the surrounding H2O shell. The res ults are rationalized in terms of an incorporation model which replace s a single phosphate ion by a CrCl2(H2O)(4)(+) complex. It is proposed that formal charge compensation is obtained through the removal of tw o hydrogen-bonding protons, from adjacent phosphate groups, and two ad jacent ammonium cations.