The standard enthalpies of formation of some intermetallic compounds of early 4d and 5d transition metals by high temperature direct synthesis calorimetry

The standard enthalpies of formation of some intermetallic compounds of early 4d and 5d transition metals have been measured by high temperature direct synthesis calorimetry at 1373±2 K. The following results (in kJ/mol of atoms) are reported: ZrMn2(−24.7±2.7); ZrMo2(−5.8±5.3); Zr11Os4(−8.9±2.1); HfCr2(−4.8±4.3); HfMn2(−20.3±2.0); HfMo2(−6.4±4.3); NbRh3(−21.6±1.8); TaRh3(−14.0±4.0). The values are compared with the predicted values of Miedema and co-workers, and with new results of ab initio calculations, where available. We will present a systematic picture of how the enthalpies of formation may be related to the atomic number of the transition metal. We will also discuss some of the properties of the Laves phases among the compounds we studied.