THE PHASE-DIAGRAMS OF BETA-RH2- RESULTS OF MEAN-FIELD CALCULATIONS(X SYSTEMS (R=LA, CE, TB) )

In recent publications, we had proposed phase diagrams in the beta-pha se regions of RH2+x systems (R=La, Ce, Tb), using the mean-field appro ximation of the static concentration waves theory, applied to the subs ystem of the octahedral x-hydrogen atoms (H-O-atoms). A comparison wit h experimental data shows that a much better agreement can be obtained when the concentration-dependent lattice contraction is taken into ac count through a linear variation of the energy constants characterizin g the H-O-H-O interaction. The modified calculated phase diagrams are presented.