Investigation of structural changes near the critical point in liquid Ga-Pb alloys using an acoustic method

The anomalous temperature dependence of the sound velocity above the liquid-liquid coexistence curve in the Ga-Pb system is associated with the critical fluctuations. A fit of the Fixman theory of the sound velocity data at the critical composition allows determination of the correlation length zeta. On the other hand, the temperature dependence of zeta of the alloy with critical composition can be calculated in frames of the two-scale-factor universality hypothesis using interfacial tension data. Recently we proposed a new method of extracting the values of the liquid-liquid interfacial tension and densities of contacting phases along the coexistence curve from the results of acoustic measurements. The correlation length values determined from the sound velocity and interfacial tension measurements are in a good agreement to each other and in a reasonable agreement with the results of small-angle scattering experiments. All the critical exponents are determined by two exponents only, beta and mu, which can be obtained from the coexistence curve, density and interfacial tension data.