title: Phase behavior of a binary fluid mixture of quadrupolar molecules.
abstract: We propose a model molecule to investigate microscopic properties of a binary mixture with a closed-loop coexistence region. The molecule is comprised of a Lennard-Jones particle and a uniaxial quadrupole. Gibbs ensemble Monte Carlo simulations demonstrate that the high-density binary fluid of the molecules with the quadrupoles of the same magnitude but of the opposite signs can show closed-loop immiscibility. We find that an increase in the magnitude of the quadrupoles causes a shrinkage of the coexistence region. Molecular dynamics simulations also reveal that aggregates with two types of molecules arranged alternatively are formed in the stable one-phase region both above and below the coexistence region. String structures are dominant below the lower critical solution temperature, while branched aggregates are observed above the upper critical solution temperature. We conclude that the anisotropic interaction between the quadrupoles of the opposite signs plays a crucial role in controlling these properties of the phase behavior.
authors.affiliation: Department of Chemistry, Tohoku University, Sendai, 980-8578, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Toda
authors.affiliation: Department of Chemistry, Tohoku University, Sendai, 980-8578, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Kajimoto
authors.affiliation: Department of Chemistry, Tohoku University, Sendai, 980-8578, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Toyouchi
authors.affiliation: Department of Physics, Tohoku University, Sendai, 980-8578, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Kawakatsu
authors.affiliation: Mathematical Institute, Tohoku University, Sendai, 980-8578, Japan.
authors.forename: Yohji
authors.initials: Y
authors.lastname: Akama
authors.affiliation: Mathematical Institute, Tohoku University, Sendai, 980-8578, Japan.|WPI-AIMR, Tohoku University, Sendai, 980-8577, Japan.
authors.forename: Motoko
authors.initials: M
authors.lastname: Kotani
authors.affiliation: Department of Chemistry, Tohoku University, Sendai, 980-8578, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukumura