Crystal structure of β-Cu₂P₂O₇

Abstract

The crystal structure of β-CU 2 P 2 O 7 has been determined by X-ray methods. The crystals are monoclinic with a = 6.827(8) Å, b = 8.118(10) Å, c = 4.576(6) Å, β = 108.85(10)°, Z = 2, and space group C2/m. This structure is analogous to that of the mineral thortveitite and the high temperature forms of the pyrophosphates of Zn, Mg, and Mn. The cations are octahedrally coordinated to oxygen atoms with equatorial Cu—O bonds of 2.00 Å and 1.94 Å while the axial bond lengths are 2.58 Å. The anion has inner P—O bonds of 1.542 Å and average terminal bonds of 1.509 Å. In addition to the usual refinement with anisotropic thermal parameters, the structure has been refined in terms of a disordered structure generated from the low temperature α form of CU 2 P 2 O 7 . This disordered model agrees as well with the data (R = 0.12) as the structure based on the thortveitite structure with large anisotropic motion assigned to the atoms.