Thermodynamic study of the gaseous molecules Al2N, AlN, and Al2N2 by Knudsen cell mass spectrometry

Abstract

The Knudsen effusion mass spectrometric method has been employed to measure the equilibrium partial pressures of the Al2N molecule over the AlN–Au–graphite system. Theoretical computations were carried out to determine the structure, molecular parameters, and thermodynamic properties of Al2N. The partial pressures have been combined with the calculated thermal functions to determine the atomization enthalpy, ΔaH0o, and enthalpy of formation, ΔfH298.15o, in kJ mol−1, of 783.2±15 and 342.7±15 for Al2N, respectively. Upper values for the dissociation energy of AlN, D0o(AlN,g)⩽368±15 kJ mol−1, and for the atomization enthalpy of Al2N2, ΔaH0o(Al2N2,g)⩽1402 kJ mol−1 have been obtained. These results are discussed and compared with recent theoretical literature values.