Thermodynamics of Rare-Earth–Carbon Systems. I. The Cerium–Carbon System

The gaseous phase in thermodynamic equilibrium with the condensed cerium–carbon system has been investigated by means of the combined Knudsen-cell–mass-spectrometric technique in the temperature range 1990°–2300°K. In addition to cerium atoms, the gaseous carbide molecules CeC2 and CeC4 were identified and their partial pressures measured. Using this information, the following dissociation and atomization energies were derived: D0° = 162 ± 2 kcal/mole for the Ce–C2 bond energy in CeC2; ΔH0° = 304.5 ± 1.5 kcal/mole for the atomization energy of CeC2; ΔH0° = 609 ± 5 kcal/mole for the atomization energy of CeC4. A heat of formation for the solid cerium dicarbide was also obtained.