Liquid–liquid phase transition in one-component fluids
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چکیده
When speaking of liquid–liquid transitions, one usually thinks of multi-component systems such as fluid mixtures. In fact, as is well known, these systems are not always miscible and may separate into two fluids with different concentrations and densities. In the last few years the possibility that single-component systems may also exhibit a liquid–liquid transition has received considerable attention. Recent experimental results [1] indicate that phosphorus can have a high-density-liquid (HDL) and a low-density-liquid (LDL) phase. A first-order transition between two liquids of different densities [2] is consistent with experimental data for a variety of materials including single-component systems such as water [3–6], silica [7] and carbon [8]. Moreover, molecular dynamics (MD) simulations of specific models for supercooled water [2, 9], liquid carbon [10] and supercooled silica [11] predict a LDL–HDL critical point. Several explanations have been developed to explain the liquid–liquid phase transition, based on the use of anisotropic potentials [2, 9–11] or on two-liquid models [12]. Recently [13,14] it was shown through numerical simulation and theoretical approaches that the presence of a LDL and a HDL can arise solely from an isotropic interaction potential with an attractive part and with two characteristic short-range repulsive distances. In molecular liquid phosphorus as well as in water, expanded and compact structures compete with each other and are preferred respectively at low and high pressures and temperatures [1, 4, 6]. This suggests a pair interaction with two characteristic distances. The first distance can be associated with the hard-core exclusion between two particles and the second distance with a weak (soft-core) repulsion which can be overcome at large pressure.
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تاریخ انتشار 2002