8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P2.71Water-like anomalies in core-softened system: trajectorydependence of anomalous behaviorValentin Ryzhov, 1 Yury Fomin, 1 and Elena Tsiok 11 Institute for High Pressure Physics, Russian Academy of Sciences, Kaluzhskoe sh. , 14,142190, Troitsk, Moscow Region, Russian FederationIt is well known that some liquids (for example, water, silica, silicon, carbon, phosphorus, andsome biological systems) show an anomalous behavior in the vicinity of their freezing lines. Thewater phase diagrams have regions where a thermal expansion coefficient is negative (densityanomaly), self-diffusivity increases upon compression (diffusion anomaly), and the structuralorder of the system decreases with increasing pressure (structural anomaly). As it was discussedin many works, the presence of two length scales in the core-softening potential may be theorigin of water-like anomalies. In the present talk we report a molecular dynamics study of thecore-softened system and show that the existence of the water-like anomalies in this system [1-4]depends on the trajectory in P − ρ − T space along which the behavior of the system is studied.For example, diffusion and structural anomalies are visible along isotherms, but disappears alongthe isochores and isobars. It may be no signature of a particular anomaly along a particulartrajectory, but the anomalous region for that particular anomaly can be defined when all possibletrajectories in the same space are examined. It is shown that if the potential has an attractive part,the diffusion anomaly appears along isobars. It is shown that the validity of the Rosenfeld entropyscaling relation for the diffusion coefficient also depends on the trajectory in the P − ρ − T spacealong which the kinetic coefficients and the excess entropy are calculated.[1] Yu. D. Fomin, N. V. Gribova, V. N. Ryzhov, S. M. Stishov, and Daan Frenkel, J. Chem. Phys.129, 064512 (2008).[2] N. V. Gribova, Yu. D. Fomin, Daan Frenkel, V. N. Ryzhov, Phys. Rev. E 79, 051202 (2009).[3] Yu. D. Fomin, V. N. Ryzhov, and N. V. Gribova, Phys. Rev. E 81, 061201 (2010).[4] Yu. D. Fomin, E. N. Tsiok, and V. N. Ryzhov, J. Chem. Phys. 134, 044523 (2011).71