ANALYSIS OF THE MELTING TEMPERATURES OF RT2 COMPOUNDS (MGCU2 STRUCTURE) (R=RARE EARTH, T=MN, FE, CO, NI, RU, RH, PD, OS, IR, PT) AND RT2X2 COMPOUNDS (R=LA, CE, SM, ER T=MN, FE, CO, NI, CU, RU, RH, PD, PT X=SI,GE)

Physico-chemical analysis techniques, including X-ray phase analysis a nd differential thermal analysis were employed for the characterisatio n of compounds including their melting temperature. The melting temper ature for 70 RT2X2 compounds has been measured (R = (La, Ce, Sm, Er, T m), T = (Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Pt), X = (Si, Ge)). It is est ablished, that the compounds CePt2Ge2, LaPt2Si2, LaPt2Ge2 belong to th e CaBe2Ge2 structure type (group P4/mmm): LaPt2Si2 (a = 0.4280(2) nm, c = 0.9831(6) nm); LaPt2Ge2 (a = 0.4417(3) nm, c = 0.976(2) nm) and Ce Pt2Ge2 (a = 0.44033(4) nm, c = 0.9808(1)). An empirical model able to describe the melting temperature of T-m of the compounds RT2, RT2X2 wi th accuracy often better than 5% is presented: T-m = const/V-1/3, wher e the constant factor depends on the type of atoms constituting the co mpound, and where V is unit cell volume. (C) 1997 Elsevier Science S.A .