First-principles simulations of local structure contrast for liquid Ge1Sb2Te4, Ge2Sb2Te5, and Ge4Sb1Te5 alloys

► The element couple state of Ge1Sb2Te4 and Ge2Sb2Te5 is better than that of Ge4Sb1Te5. ► The decrease of average coordination number leads to faster atomic motion in liquid. ► The lowest compositional disorder number of Ge2Sb2Te5 indicates the best stability. ► All Ge1Sb2Te4, Ge2Sb2Te5, and Ge4Sb1Te5 liquids mainly retain octahedral local structure.