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

Thu 811:10-14:00P8.9Critical loci emanating from water’s second critical pointClaudio A. Cerdeiriña 1 and Pablo G. Debenedetti 21 Universidad de Vigo, Departamento de Física Aplicada, 32004, Ourense, Spain2 Princeton University, Princeton (New Jersey), United States of AmericaA direct proof of the existence of water’s second (liquid-liquid) critical point has been historicallyelusive [1], indirect routes of analysis are being explored as a result. One such approach concernsthe locus of maxima of the correlation length in the one-phase region, the so-called Widom line,which, obviously, originates at the critical point [2]. Secondly, in order to avoid crystallization,experiments in confining geometries are being conducted [3]. Thirdly, upon the addition of asolute, the liquid-liquid critical point of bulk water must develop a critical line. This idea wasintroduced and exploited in 2006 [4], and is being currently analyzed via simulations (see, e. g. ,Ref. 5). The question arises whether loci emanating from water’s liquid-liquid critical point extendto experimentally accessible regions; and if so, under what specific conditions? Here we presentexplicit results for such critical loci from a model of dilute aqueous solutions. By incorporatingsmall-length-scale hydrophobicity, we extend the water model by Poole et al. [6] to mixtures ofnonpolar solutes. Analytic solutions obtained using a method introduced by Tisza (see Ref. 7) areexpected to stimulate further experimental studies, which eventually could tell us something aboutthe connections, if any, between hydrophobicity and water anomalous thermodynamics.[1] P. G. Debenedetti, J. Phys. : Condens. Matter 15, R1669 (2003).[2] G. Franzese and H. E. Stanley, J. Phys. : Condens. Matter 19, 205126 (2007).[3] P. Gallo, M. Rovere, S. H. Chen, J. Phys. Chem. Lett. 1, 729 (2010).[4] S. Chatterjee and P. G. Debenedetti, J. Chem. Phys. 124, 154503 (2006).[5] D. Corradini, S. V. Buldyrev, P. Gallo, H. E. Stanley, Phys. Rev. E 81, 061504 (2010).[6] P. H. Poole, F. Sciortino, T. Grande, H. E. Stanley, C. A. Angell, Phys. Rev. Lett. 73, 1632(1994).[7] Y. C. Kim and M. E. Fisher, J. Phys. Chem. B 105, 11785 (2001).9