Dissociation energies of the molecules RhTh and RhU from high temperature mass spectrometry and predicted thermodynamic stabilities of selected diatomic actinide–platinum metal intermetallic molecules

Abstract

Gaseous RhTh and RhU have been observed in a Knudsen effusion mass spectrometric investigation of a thorium–uranium‐rhodium–graphite system at high temperatures (2400–2700 °K). Thermodynamic treatment of the experimental data yielded the atomization energies of RhTh and RhU as D⁰₂₉₈(RhTh) =513±21 kJ mole⁻¹ or 122.6±5 kcal mole⁻¹ and D⁰₂₉₈(RhU) =519±17 kJ mole⁻¹ or 124.0±4 kcal mole⁻¹. These values were derived from the third law enthalpies of the following reactions. The known experimental bond energies for the ligand‐free gaseous intermetallic compounds between the actinides and the platinum metals have been interpretated in terms of a previously developed model based on the Brewer–Engel approach. Also, calculations are presented for the dissociation energies of certain selected actinide–platinum metal diatomic molecules which have not yet been experimentally observed.