Phase-equilibrium data are presented for the system LiF-BeF2 and for the BeF2 end of the systems NaF-BeF2 and RbF-BeF2. The systems LiF-BeF2 and NaF-BeF2 are weakened models, respectively, of ZnO-SiO2 and CaO-SiO2 but with the notable difference that liquid immiscibility does not appear in the fluoride systems. The melting point of the cristobalite form of BeF2 has been determined as 543°± 5°C. and that of the willemite model (Li2BeF4) as 458 ± 5°C. Data obtained for the compound Na2LiBe2F7 show that its structure is ver...
