The bulk viscosity of a symmetrical Lennard–Jones mixture above and at liquid–liquid coexistence: A computer simulation study

Abstract A Lennard–Jones model of a binary dense liquid (A,B) with a symmetrical miscibility gap is investigated by means of computer simulation methods. Semigrand–canonical Monte Carlo simulations yield the phase diagram in the T–x plane (T : temperature, x: concentration of A or B particles) as well as equilibrated configurations at coexistence. Then Molecular Dynamics simulations use these configurations to determine static properties (isothermal compressibility κT and concentration susceptibility χ) as well as the shear and the bulk viscosity ηs and ηB, respectively. The latter quantities are calculated along a path approaching the coexistence line from high temperatures in the one–phase region and ending at a state at the coexistence line about 15% below the critical point. We find that κT and χ increase significantly near the coexistence line reflecting the vicinity of the critical point. Whereas ηs exhibits a weak temperature dependence, ηB increases significantly near the coexistence curve.