Two hydrides exist in the Tb-H system. Terbium dihydride (nominal formula TbH2) has the fcc structure (type CaF2) with lattice parameter a = 0.5246 nm. Terbium tryhidride (nominal formula TbH3) has a hexagonal structure, with lattice parameters a = 0.6409 nm, c = 0.6658 nm. The homogeneity range of terbium dihydride is TbH1.9-2.3 [62Peb, 76McQ].
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