title: A molecular dynamics study of the equation of state and the structure of supercooled aqueous solutions of methanol.
abstract: We perform molecular dynamics computer simulations in order to study the equation of state and the structure of supercooled aqueous solutions of methanol at methanol mole fractions x(m) = 0.05 and x(m) = 0.10. We model the solvent using the TIP4P/2005 potential and the methanol using the OPLS-AA force field. We find that for x(m) = 0.05 the behavior of the equation of state, studied in the P - T and P - ρ planes, is consistent with the presence of a liquid-liquid phase transition, reminiscent of that previously found for x(m) = 0. We estimate the position of the liquid-liquid critical point to be at T = 193 K, P = 96 MPa, and ρ = 1.003 g/cm(3). When the methanol mole fraction is doubled to x(m) = 0.10 no liquid-liquid transition is observed, indicating its possible disappearance at this concentration. We also study the water-water and water-methanol structure in the two solutions. We find that down to low temperature methanol can be incorporated into the water structure for both x(m) = 0.05 and x(m) = 0.10.
authors.affiliation: Center for Polymer Studies and Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, USA. darcorr@buphy.bu.edu
authors.forename: Dario
authors.initials: D
authors.lastname: Corradini
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Su
authors.forename: H Eugene
authors.initials: HE
authors.lastname: Stanley
authors.forename: Paola
authors.initials: P
authors.lastname: Gallo
mesh_terms: D000432:Methanol / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D012996:Solutions; D014867:Water / Q000737:chemistry
chemical_list: D012996:Solutions; D014867:Water; D000432:Methanol