THE CRYSTAL STRUCTURE OF α-Zn 3 (PO 4 ) 2

α-Zn 3 (PO 4 ) 2 crystallized in the monoclinic space group C2/c with lattice parameters a = 8.14 ± 0.02 Å, b = 5.63 ± 0.01 Å, c = 15.04 ± 0.04 Å, β = 105°08′ ± 05′, and Z = 4. The cations are found in two types of tetrahedrally coordinated sites. One-third of the cations lie on twofold axes within an oxygen tetrahedron. The remaining cations are found in a pair of edge-sharing oxygen atom tetrahedra. The green emission of Mn ++ in α-Zn 3 (PO 4 ) 2 is consistent with Mn ++ substituting for Zn ++ in either tetrahedral site.