Energetics of copper diphosphates – Cu2P2O7 and Cu3(P2O6OH)2 |
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| Authors: | So-Nhu Le Alexandra Navrotsky Valerie Pralong |
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| Affiliation: | aThermochemistry Facility, NEAT ORU, and Chemistry Department, University of California at Davis, Davis, CA 95616, USA;bLaboratory Crismat, UMR 6508 CNRS ENSICAEN, 6 bd Marechal Juin, 14050 Caen Cedex, France |
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| Abstract: | Differential scanning calorimetry and high temperature oxide melt solution calorimetry are used to study enthalpy of phase transition and enthalpies of formation of Cu2P2O7 and Cu3(P2O6OH)2. α-Cu2P2O7 is reversibly transformed to β-Cu2P2O7 at 338–363 K with an enthalpy of phase transition of 0.15 ± 0.03 kJ mol−1. Enthalpies of formation from oxides of α-Cu2P2O7 and Cu3(P2O6OH)2 are −279.0 ± 1.4 kJ mol−1 and −538.8 ± 2.7 kJ mol−1, and their standard enthalpies of formation (enthalpy of formation from elements) are −2096.1 ± 4.3 kJ mol−1 and −4302.7 ± 6.7 kJ mol−1, respectively. The presence of hydrogen in diphosphate groups changes the geometry of Cu(II) and decreases acid–base interaction between oxide components in Cu3(P2O6OH)2, thus decreasing its thermodynamic stability. |
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| Keywords: | Cu2P2O7 Cu3(P2O6OH)2 Copper phosphate Enthalpy of formation Phase transformation |
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