A Theoretical and Experimental Study of the Enthalpies of Formation of LaNi₅‐Type Compounds

Abstract

The heats of formation of LaNi,-type compounds are computed within a tight-binding scheme for the d-band. It is shown that the relatively large difference between the energy levels of the two elements is a dominant factor in the determination of the formation energy. The evolution of the energy level of the rare-earth metal can explain the experimental behaviour of the heats of formation of the RNi, compounds along the rare-earth series. I n order to discuss the calculated reeults the enthalpies of formation of LaNi,, PrNi,, SmNi,, and YNi, are determined by a calorimetric method.Die Bildungswirmen von LaNi,-Verbindungen werden numerisch innerhalb eines "tight-binding"-Modells fur das d-Band berechnet. Es wird gezeigt, daB die relativ grol3e Differenz zwischen den Energieniveaus der beiden Elemente ein dominierender Faktor bei der Bestimmung der Bildungsenergie ist. Die Entwicklung des Energieniveaus des Seltenerd-Metalls kann das experimentelle Verhalten der Bildungswirmen der RNi,-Verbindungen in der Serie deI Seltenen Erden erklaren. Um die berechneten Ergebnisse zu diskutieren, werden die Bildungsenthalpien von LaNi,, PrNi,, SmNi, und YNi, mittels kalorimetrischen Methoden bestimmt.

Thermochemistry of binary alloys of lanthanum with 3d-transition metals

“…For all of the test alloys the considerable exothermic effects were established for alloy formation increasing in the REM series from La to Lu. This thermochemical behavior agrees with data for the enthalpy of formation of solid alloys [6] and the nature of phase equilibria in binary systems [7].…”

“…For alloys of lanthanum with 3d-metals there is practical interest (thermoelectric materials, amorphous alloys, hydrogen accumulators [6]) and values of the enthalpy of mixing over a wide range of concentration have only been obtained for alloys with Mn, Co, Ni, and Cu [1]; the data are limited for other systems (La − Fe [8]), or they are entirely absent (alloys of lanthanum with Sc, Ti, V, and Cr).…”

Formation of Sm(Co1–xNix)5epitaxial thin films on Cu(111) underlayers

“…Figures 1(a-1)-(d-1) 17 Ni 83 variants with respect to Cu underlayer are -2.5%, -2.8%, -3.4%, and -3.6%, while those of B-type variants are +12.5%, +12.3%, +11.5%, and +11.3%. Here, the lattice constants of bulk SmCo 5 (a SmCo5 = 0.4982 nm [15]), SmNi 5 (a SmNi5 = 0.4926 nm [16]), and Cu (a Cu = 0.3615 nm [17]) crystals and the lattice constants of a SmCo4Ni (= 0.8a SmCo5 +0.2a SmNi5 ) and a SmCoNi4 (= 0.2a SmCo5 +0.8a SmNi5 ), which are estimated by using the lattice constants of a SmCo5 and a SmNi5 , are used. Although there are fairly large mismatches in the cases of B-type variants, epitaxial growth is taking place.…”

Ordered phase formation in Sm-Ni thin film deposited on Cr(100) single-crystal underlayer

“…The result suggests that the film is strained around the SmNi 5 /Cr interface due to the lattice mismatch and the strain decreases with increasing the thickness. Figure 2 [15]). This is due to an influence of lattice mismatches at the SmNi 5 /Cr interface along SmNi 5 [0001] (-2.4%) and SmNi 5 [1 1…”

“…The magnetization curves were measured by using a vibrating sample magnetometer. 00] are respectively calculated to be -2.4% and +5.0%, where the lattice constants of bulk SmNi 5 (a = 0.4926 nm, c = 0.3980 nm [15]) and Cr (a = 0.2884 nm [17]) crystals are used. Although there exists such a large misfit of -5.0% along SmNi 5 [11 _ 00], epitaxial growth of SmNi 5 crystal on Cr(100) underlayer is taking place.…”