Enthalpies homonuclear diatomics

The value of the maximum dissociation energy in a homonuclear diatomic transition metal molecule has been predicted (2) to be (600 40) kJ mol-1 for ditantalum. The dissociation energies of homonuclear transition metal molecules have been predicted by various methods of which the most recent is the cell model of Miedema (7). This proposes a relation between the enthalpy of vaporisation of the solid metal, AH ap, the dissociation energy, D°, of the diatomic molecule and the surface energy of the metal, Y° as follows,... 

The dissociation energies of the homonuclear diatomic molecules, D (R2), were calculated from the mass spectrometrically measured ion currents and the thermal functions evaluated for the gaseous species. The error limits shown in table 1 are upper limits and include those due to experimental uncertainties and also those due to the uncertainties in calculated thermal functions. The Do(R2) values (last column, table 1) also show the double periodicity exhibited by the sublimation enthalpies. This double periodicity comes about because (1) in the thermodynamic calculations the of th rare-earth metals is needed,... 

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