C. Colinet

Enthalpies of formation of liquid and solid binary alloys of lead, antimony and bismuth with rare earth elements

Abstract The predictions of Miedemas model for the heats of formation of binary intermetallic compounds of lead, bismuth and antimony with rare earth elements and for the heats of mixing and solution of the corresponding liquid alloy systems are presented. The predicted values are compared with the existing experimental data. The differences between the experimental and the calculated values of the enthalpy are discussed.

Experimental and calculated enthalpies of formation of rare earth-tin alloys

Abstract The partial enthalpies of some rare earth elements (lanthanum, cerium, thulium, lutetium and yttrium) at infinite dilution in liquid tin were determined by means of a calorimetric method. The change in this thermodynamic property with atomic number is discussed in terms of the contribution of the 4f electrons to the bonding. This assumption is used to calculate the hybridization term involved in Miedemas relation. Experimental results therefore allow an accurate determination of the parameters of Miedemas relation. These are used to calculate the enthalpies of formation of rare earth-tin compounds. The predicted values are compared with available experimental data.

Electronic structure and enthalpies of formation of Gd(Ni, Co, Fe)2 compounds

Abstract The electronic density of states in GdNi 2 , GdCo 2 and GdFe 2 compounds are calculated in the tight-binding d-band model by the moment method. We show a clear correlation between the position of the Fermi level in the density of states of these compounds and their enthalpies of formation which have been measured by a calorimetric method involving dissolution of the compounds in molten aluminium.

Enthalpies of formation of the LaCu intermetallic phases

Abstract The enthalpies of formation of the various intermetallic phases of the LaCu binary system were measured by a calorimetric method involving the dissolution of the compounds in molten Al. The experimental results were compared with the values predicted by the Miedema representation.

Thermodynamic study of the valence state of cerium and hydrogen storage in Ce(Ni1−xCux)5 compounds☆

The enthalpies of formation of the pseudo-binary Ce(Ni1−xCux)5 compounds, measured by the calorimetric method, were found to increase linearly from CeNi5 to CeCu5. The valence state of cerium in Ce(Ni1−xCux)5 is discussed by comparison with the La(Ni1−xCux)5 system. The enthalpies of hydrogenation of Ce(Ni1−xCux)5 are calculated from their enthalpies of formation using relations previously established, and compared with experimental data from literature.

Theoretical description of phase equilibrium in the nickel-titanium system

Solid-solid and solid-liquid phase equilibrium in the Ni-Ti system is studied within the framework of the cluster variation method (CVM). The energy parameters entering the free-energy description of each phase are determined by tight-binding energy calculations using the cluster Bethe lattice method (CBLM). For simplicity, the pair interactions are restricted to first-nearest neighbours in FCC-based structures and to first- and second-nearest neighbours in BCC-based structures. The configurational entropy for disordered solutions and for ordered compounds are obtained using the tetrahedron approximation of the CVM. The three compounds NiTi, Ni3Ti and NiTi2 compounds are treated as stoichiometric compounds. The calculated diagram agrees reasonably well with that determined experimentally.

Phase stability in Ni-Ti alloys

A tight-binding bond model is used for a quantitative study of electronic interactions in nickel-titanium compounds. The model is not an ab initio calculation but it requires only the data on the elemental properties of pure metal constituents that are readily available in the literature. Combined with an extended cluster Bethe lattice method (CBLM) for FCC- and BCC-based solid solutions and the B2 phase, and the recursion method for NiTi2 and Ni3Ti stoichiometric compounds, this approach allows the energy of formation of these alloys to be calculated and the chemical trends in the ordering effects to be analysed.