Institute for High Pressure Physics RAS, 142190 Troitsk Moscow Region, Russia.
J Phys Chem B. 2011 Dec 8;115(48):14112-5. doi: 10.1021/jp2039898. Epub 2011 Jun 24.
The locus of extrema (ridges) for heat capacity, thermal expansion coefficient, compressibility, and density fluctuations for model particle systems with Lennard-Jones (LJ) potential in the supercritical region have been obtained. It was found that the ridges for different thermodynamic values virtually merge into a single Widom line at T < 1.1T(c) and P < 1.5P(c) and become practically completely smeared at T < 2.5T(c) and P < 10P(c), where T(c) and P(c) are the critical temperature and pressure. The ridge for heat capacity approaches close to critical isochore, whereas the lines of extrema for other values correspond to density decrease. The lines corresponding to the supercritical maxima for argon and neon are in good agreement with the computer simulation data for LJ fluid. The behavior of the ridges for LJ fluid, in turn, is close to that for the supercritical van der Waals fluid, which is indicative of a fairly universal behavior of the Widom line for a liquid-gas transition.
已获得具有 Lennard-Jones (LJ) 势能的模型粒子系统在超临界区的热容、热膨胀系数、压缩性和密度涨落的极值脊（脊线）。研究发现，在 T < 1.1T(c) 和 P < 1.5P(c) 下，不同热力学值的脊线几乎合并成一条 Widom 线，而在 T < 2.5T(c) 和 P < 10P(c) 下，脊线几乎完全模糊，其中 T(c) 和 P(c) 是临界温度和压力。热容的脊线接近临界点等容线，而其他值的极值线对应于密度减小。与 LJ 流体的计算机模拟数据相比，氩和氖的超临极值线吻合较好。LJ 流体的脊线行为反过来又与超临界范德华流体的行为接近，这表明 Widom 线在液-气转变中具有相当普遍的行为。
