Molecular dynamics simulations of CCl4–H2O liquid–liquid interface with polarizable potential models

The results from molecular dynamics simulations of the equilibrium properties of the CCl4–H2O liquid–liquid interface at room temperature are presented. The interactions between H2O–H2O, H2O–CCl4, and CCl4–CCl4 are described using the polarizable potential models developed in our laboratory. To our knowledge, this work is the first molecular dynamics simulations of the liquid–liquid interfacial equilibrium properties that explicitly includes nonadditive polarization effects. Molecular dynamics results of a 300 ps simulation following an extensive equilibration process indicate that the liquid interface is very stable, the density profile of H2O is very smooth, while that of CCl4 exhibits some oscillations. It is found that locally there is a sharp transition from one liquid phase to the other, but the overall interface is broadened by thermal fluctuations as indicated by the liquid density profiles. Calculated radial distribution functions suggest that the local structures of CCl4 and H2O remain unchanged from the bulk liquid to the interface. However, the interface does induce orientational order of H2O and CCl4 molecules. To study the polarization effects on the liquid–liquid interfacial equilibrium properties, we have calculated the total and induced dipole moments of H2O and CCl4 molecules as a function of the distance normal to the interface. The calculated dipole moments of the water molecules near the interface are close to their gas phase values, while water molecules far from the interface have dipole moments corresponding to the bulk values. This behavior can be attributed to the changes of the hydrogen bonding patterns and the orientation of water molecules near the interface. The induced dipole moments of the CCl4 molecules near the interface, on the other hand, are significantly enhanced. This is due in part to the strong local field induced by the water molecules at the interface. The calculated electric potentials using the dipole moment approach help us to analyze the orientations of water and CCl4 molecules at the interface.

[1]  M. Matsumoto,et al.  Study on liquid–vapor interface of water. I. Simulational results of thermodynamic properties and orientational structure , 1988 .

[2]  D. Higgins,et al.  Second Harmonic Generation Studies of Adsorption at a Liquid-Liquid Electrochemical Interface , 1993 .

[3]  Theo Rasing,et al.  Orientation of Molecular Monolayers at the Liquid-Liquid Interface As Studied by Optical Second Harmonic Generation , 1988 .

[4]  Herman J. C. Berendsen,et al.  A Molecular Dynamics Study of the Decane/Water Interface , 1993 .

[5]  Smit.  Molecular-dynamics simulations of amphiphilic molecules at a liquid-liquid interface. , 1988, Physical review. A, General physics.

[6]  Determination of Atomic Charges Including solvation and Conformational Effects , 1994 .

[7]  K. Eisenthal.  Equilibrium and Dynamic Processes at Interfaces by Second Harmonic and Sum Frequency Generation , 1992 .

[8]  Shen,et al.  Vibrational spectroscopy of water at the vapor/water interface. , 1993, Physical review letters.

[9]  Anders Wallqvist,et al.  A molecular dynamics study of polarizable water , 1989 .

[10]  L. Benjamin.  Mechanism and Dynamics of Ion Transfer Across a Liquid-Liquid Interface , 1993, Science.

[11]  W. Hehre,et al.  A molecular dynamics study of the hexane/water interface , 1990 .

[12]  I. Benjamin,et al.  Transfer of Small Ions across the Water/1,2-Dichloroethane Interface , 1995 .

[13]  Michiel Sprik,et al.  Molecular dynamics simulation of an aqueous sodium octanoate micelle using polarizable surfactant molecules , 1993 .

[14]  Peter A. Kollman,et al.  Cation-.pi. Interactions: Nonadditive Effects Are Critical in Their Accurate Representation , 1995 .

[15]  L. Dang,et al.  The nonadditive intermolecular potential for water revised , 1992 .

[16]  J. A. Barker,et al.  Surface structure and surface tension: perturbation theory and Monte Carlo calculation , 1974 .

[17]  J. R. Carl,et al.  Atom dipole interaction model for molecular polarizability. Application to polyatomic molecules and determination of atom polarizabilities , 1972 .

[18]  M. Hayoun,et al.  Computer modeling of a liquid–liquid interface , 1988 .

[19]  Kirk A. Peterson,et al.  Molecular dynamics simulations of liquid, interface, and ionic solvation of polarizable carbon tetrachloride , 1995 .

[20]  I. Benjamin,et al.  MOLECULAR DYNAMICS OF ADIABATIC AND NONADIABATIC ELECTRON TRANSFER AT THE METAL-WATER INTERFACE , 1994 .

[21]  P. Linse.  Monte Carlo simulation of liquid–liquid benzene–water interface , 1987 .

[22]  I. Benjamin.  Theoretical study of the water/1,2‐dichloroethane interface: Structure, dynamics, and conformational equilibria at the liquid–liquid interface , 1992 .

[23]  J. Banavar,et al.  Computer Simulation of Liquids , 1988 .

[24]  Peter A. Kollman,et al.  Implementation of nonadditive intermolecular potentials by use of molecular dynamics: development of a water-water potential and water-ion cluster interactions , 1990 .

[25]  F. Abraham,et al.  The interfacial density profile of a Lennard‐Jones fluid in contact with a (100) Lennard‐Jones wall and its relationship to idealized fluid/wall systems: A Monte Carlo simulation , 1978 .

[26]  D. Tildesley,et al.  Molecular dynamics simulation of the orthobaric densities and surface tension of water , 1995 .

[27]  J. Conboy,et al.  Studies of Alkane/Water Interfaces by Total Internal Reflection Second Harmonic Generation. , 1994 .

[28]  A. D. McLean,et al.  Monte Carlo simulation of the liquid-vapor interface of water using an ab initio potential , 1993 .

[29]  G. Ciccotti,et al.  Numerical Integration of the Cartesian Equations of Motion of a System with Constraints: Molecular Dynamics of n-Alkanes , 1977 .

[30]  C. Croxton.  Molecular orientation and interfacial properties of liquid water , 1981 .

[31]  A. Pohorille,et al.  Surface potential of the water liquid-vapor interface. , 1988, The Journal of chemical physics.

[32]  Herman J. C. Berendsen,et al.  Simulation of Water Transport through a Lipid Membrane , 1994 .

[33]  Arieh Warshel,et al.  Investigation of the free energy functions for electron transfer reactions , 1990 .