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

P2.28Tue 611:23-14:00Ultrasonic evidence for low density water to high densitywater transitionEduardo Hidalgo, 1 Mercedes Taravillo, 1 Valentín Garcia Baonza, 1 Pedro DimasSanz, 1 and Bérengère Guignon 11 MALTA-Consolider Team, Universidad Complutense de Madrid, Dep. Quimica Fisica,Fac. Quimicas, Ciudad Universitaria S/N 28040, Madrid, SpainThe possible existence of a transition between a low density (LDW) and high density (HDW)forms of water have been a matter of study in recent years from different approaches. In thetemperature (273 K to 400 K) and pressure (up to 1 GPa) ranges where different available dataexist, the conclusions are somewhat contradictory. Thus, molecular dynamics calculations [1] andBrillouin scattering measurements [2] suggest a decrease in the transition pressure with increasingtemperature, while Raman spectroscopy [3] and compressibility [4] analyses suggest just theopposite behavior. In order to shed some light into this question, we have performed a seriesof speed of sound measurements from 253 to 348 K and up to 700 MPa. On the basis of thesemeasurements and existing Raman results from our laboratory we are able to reconcile all theexisting data by introducing a new interpretation of the LDW-HDW transition.[1] M. Saitta and F. Datchi, Phys. Rev. E 67, 020201 (2003).[2] F. Li et al. J. Chem. Phys. 123, 174511 (2005).[3] T. Kawamoto et al. J. Chem. Phys. 120, 5867 (2004).[4] P. W. Mirwald, J. Chem. Phys. 123, 124715 (2005).28