Crystal data for two orthorphosphates α-NaCuPO₄ and β-AgCuPO₄

Two orthophosphates M¹CuPO₄ (with M¹ = Na or Ag) have been synthesized by solid-state reaction between M₃PO₄ and Cu₃(PO₄)₂. Each of these compounds undergoes a phase transition at high temperature, for AgCuPO₄ the polymorphic transformation is irreversible. α-NaCuPO₄ (low temperature) is orthorhombic P2₁2₁2₁, a = 9.7098(8), b = 4.8040(3), c = 7.1676(6) Å, V = 334.34(7) ų, D_m (298 K) = 3.55, D_x = 3.606 Mg m⁻³, Z = 4. β-AgCuPO₄ (high temperature) is orthorhombic, Pbca, a = 7.5008(6), b = 15.749(1), c = 5.7030(5) Å, V = 673.70(14) ų, D_m(298 K) = 5.25, D_x = 5.253 Mg m⁻³ for Z = 8. Powder diffraction data have been obtained at 293 K with a counter diffractometer with Ni-filtered copper radiation (λ = 1.5418 Å). The JCPDS Diffraction File Nos. are 34-1496 for β-AgCuPO₄; 34-1497 for α-NaCuPO₄.