The　Yb-Bi　and　the　Yb-Te　systems　are　thermodynamically　assessed　by　CALPHAD　approach　based　on　the　available　experimental　data　including　thermochemical　properties　and　phase　equilibria.　All　of　the　intermetallic　phases　in　these　two　systems　are　treated　as　stoichiometric　compounds　due　to　their　unnoticeable　homogeneity　ranges,　and　their　formation　enthalpies　at　0　K　are　calculated　by　the　first-principles　method　to　supplement　the　thermochemical　property　data　for　the　present　optimization.　The　values　of　the　first-principles　calculation　are　confirmed　by　the　lattice　constants　and　the　equilibrium　modulus　of　the　compounds　available　from　experiments.　Given　the　asymmetric　shapes　of　the　liquidus　around　the　compounds　Yb4Bi3/YbTe　in　the　Yb-Bi/Te　phase　diagrams,　both　the　associate　model　and　the　sub-regular　solution　model　are　used　to　describe　the　Gibbs　free　energy　of　the　liquid　phase　for　the　two　systems.　The　comparison　between　the　optimization　results　and　the　experimental　data　for　the　Yb-Bi/Te　systems　shows　that　a　much　better　agreement　is　obtained　by　means　of　the　associate　model　than　the　sub-regular　solution　model.　(C)　2015　Elsevier　Ltd.　All　rights　reserved.