Standard enthalpies of formation for some samarium alloys, Sm + Me (Me = Ni, Rh, Pd, Pt), determined by high-temperature direct synthesis calorimetry

The standard enthalpies of formation of eight samarium alloys with late transition metals have been determined by direct synthesis calorimetry at 1273plus/minus2K. The following values of Delta H sub f exp 0 , in kJ(mole atom) exp -1 , are reported: SmNi sub 5 , -27.4plus/minus0.5; Sm sub 5 Rh sub 4 , -66.5plus/minus1.0; SmRh sub 2 , -65.5plus/minus1.2; SmPd, -82.4plus/minus2.0; Sm sub 3 Pd sub 4 , -87.2plus/minus2.5; SmPd sub 3 , -82.9plus/minus2.5; SmPt, -108.7plus/minus3.5; and SmPt sub 2 , -100.2plus/minus2.6. The results are compared with predicted values from the Miedema model, with available literature data for SmNi sub 5 , SmPd, and SmPt, and with earlier values for similar compounds formed by other lanthanide metals reported by this laboratory. The observed relationships between the enthalpies of formation and the number of f-electrons in the considered binary alloys RE sub n Me sub m (RE=lanthanide elements; and Me=Group VIII elements) are discussed.