Temperature and composition dependence of the Soret coefficientIn Lennard-Jones mixtures presenting consolute critical phenomena

摘要

Nonequilibrium molecular dynamics calculations have been carried out o Lennard-Jones binarymixtures with the aim to investigate the dependence of the Soret coefficient on the temperature andon the composition for systems presenting phase transitions. By an appropriate choice of the crossinteraction parameter, ε_(12)(0<12)< min{ε_(11),ε_(22)}) these systems show a mixing/demixing(consolute) phase transition. The other parameters are those of a binary mixture of Argon andKrypton. This system has been considered over a wide range of temperatures (up to =1000 K), ofcompositions (0.1≤x_1≤0.9), and of cross interaction parameter (0 <ε_(12)< min{ε_(11) The study})S_T,as a function oftemperature and composition. Indeed the computed values of S_Tin the one phase region outside thecritical region are closely fitted by the function T-T_c(x_1)~(-1)whereT_c(x_1)is the demixingtemperature of the mixture under study. This result indicates for this type of systems a dependenceof S_T,as a function of the temperature, on a unique characteristic property of the fluid mixture, thedemixing temperature T_c, which, in turn, is a function of the binary mixture compositionx_l.