Edinburgh Napier University

  Thermodynamic stability of model single component and binary mixture fluids is considered with the Fisher–Ruelle (FR) stability criteria, which apply in the thermodynamic limit, and molecular dynamics (MD) simulation for finite periodic systems. Two soft-core potential forms are considered, ϕ 6,1 (r)=4[1/(a+r 6 ) 2 −1/(a+r 6 )] and ϕ 2,3 (r)=4[1/(a+r 2 ) 6 −1/(a+r 2 ) 3 ] , where r is the separation between the particle centers. According to FR these are unstable in the thermodynamic limit if a>a c =1/2 and a>a c =(7/32) 1/3 , respectively. MD simulations with single-component particles show, however, that this transition on typical simulation times is more gradual for finite periodic systems with variation in a on either side of a c . For a