The temperature dependency of some of the thermodynamical properties of aqueous binary mixture systems

International Journal of Scientific & Technology Research, 2020

This molecular dynamic simulation study is made using Lammps software to compare outcome results of thermal properties of most known five rigid water models. The water has received special attention because it is commonly used base-fluid in heat transfer application. This study focuses on computing water thermal conductivity, dynamic viscosity, density, specific isobaric heat capacity, specific isochoric heat capacity. A significant outcome of this study is to compare results and suggest an optimal model which can be used to evaluate water thermal properties. Lammps, a powerful molecular dynamics software, is used to do the molecular dynamics calculation in this study. Atomic initial position, intermolecular forces, etc., are prepared using Moltemplate. Atomistic model types of water used in this study are the simple point charge (SPC) model, The extended simple point charge (SPC/E) model, The TIP-type models (TIP3PEW, TIP4PEW andTIP4-2005). This study investigates efficiency of fiv...

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1997

Some relationships have been found between the infrared spectroscopic properties of water molecules hydrogen bonded to a number of bases in binary liquid mixtures, and the partial molar excess enthalpies at infinite dilution of water of the solutions. The results suggest a new approach to the use of the well-known Badger-Bauer relationship. 0 1997 Elsevier Science B.V.

Journal of Molecular Liquids, 2007

The purpose of the present paper is to review what kind of thermophysical properties can be predicted, either qualitatively or quantitatively with molecular simulation. In a first part, the main types of molecular simulation methods are introduced. Molecular dynamics (MD) can be ...

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R Kumar # , S Jayakumar ∗ & V Kannappan + # Department of Physics, The New College, Chennai 600 014 ∗ Department of Physics, RKM Vivekananda College, Chennai 600 004 + Department of Chemistry, Presidency College, Chennai 600 005 E-mail: jk_5454@yahoo.co.in

Zeitschrift für Naturforschung A, 1976

Results of a molecular dynamics study of a 0.55 molal aqueous NaCl solution are reported. The basic periodic box contained 200 water molecules, 2 sodium ions and 2 chloride ions. The calculated properties of this solution are compared with those obtained previously for a 2.2 molal NaCl solution. The formation of second hydration shells, an increase of the number of water molecules in the first hydration shells, and a release of internal pressure are the main changes connected with a decrease of the concentration.

The Journal of Physical Chemistry, 1987

The results of molecular dynamics calculations on the equilibrium interface between liquid water and its vapor at 325 K are presented. For the TIP4P model of water intermolecular pair potentials, the average surface dipole density points from the vapor to the liquid. The most common orientations of water molecules have the C, , molecular axis roughly parallel to the interface. The distributions are quite broad and therefore compatible with the intermolecular correlations characteristic of bulk liquid water. All near-neighbor pairs in the outermost interfacial layers are hydrogen bonded according to the common definition adopted here. The orientational preferences of water molecules near a free surface differ from those near rigidly planar walls which can be interpreted in terms of patterns found in hexagonal ice 1. The mean electric field in the interfacial region is parallel to the mean polarization which indicates that attention cannot be limited to dipolar charge distributions in macroscopic descriptions of the electrical properties of this interface. The value of the surface tension obtained is 132 f 46 dyn/cm, significantly different from the value for experimental water of 68 dyn/cm at 325 K.

Polymer, 2010

An aqueous poly(vinyl alcohol) (PVA) model has been extensively studied by using the molecular dynamics (MD) simulation method. The employed molecular and force field models are validated against the available data in the literature. In particular, the glass transition temperature (T g ) is determined from the specific volume versus temperature, which compares well with the experimental observations. The diffusion coefficients of water (H 2 O) through the PVA matrix follow the Arrhenius equations at both temperature regions separated by T g , indicating the existence of free and bound water defined by hydrogen bonds (HBs). It has also been confirmed that HBs occur between PVA and H 2 O, between PVA and PVA, between H 2 O and H 2 O, and all of them play the key roles in the glass transition. The local dynamics suggested by the decorrelations of various bond vectors can be well described by the Williams eLandeleFerry (WLF) equation. This work demonstrates the cooperative behavior of PVA and H 2 O which is responsible for the glass transition of the whole binary system.

Condensed Matter Physics, 2015

We have investigated thermodynamic and dynamic properties as well as the dielectric constant of water-methanol model mixtures in the entire range of composition by using constant pressure molecular dynamics simulations at ambient conditions. The SPC/E and TIP4P/Ew water models are used in combination with the OPLS united atom modelling for methanol. Changes of the average number of hydrogen bonds between particles of different species and of the fractions of differently bonded molecules are put in correspondence with the behavior of excess mixing volume and enthalpy, of self-diffusion coefficients and rotational relaxation times. From the detailed analyses of the results obtained in this work, we conclude that an improvement of the description of an ample set of properties of water-methanol mixtures can possibly be reached, if a more sophisticated, carefully parameterized, e.g., all atom, model for methanol is used. Moreover, exploration of parametrization of the methanol force field, with simultaneous application of different combination rules for methanol-water cross interactions, is required.

Physica A: Statistical Mechanics and its Applications, 1996

A molecular dynamics simulation of a 0.1 M ethanol-water solution with an air/solution interface was performed. Redistribution of ethanol molecules was observed during the simulation, which was initiated from a bulk solution. The results of the simulation show good agreement with surface tension measurements and the number density profiles of the ethanol excess from neutron reflectivity experiments. A depletion layer beneath the ethanol surface excess was revealed by the simulation. Ethanol molecules are oriented at the surface such that the alkyl group points out of the solution. The number of water molecules involved in the hydrogen bonding with the ethanol molecules decreases by a factor of 2 between the surface and the bulk. * Corresponding author. 0378-4371/96/$15.00 Copyright (~) 1996 Elsevier Science B.V. All fights reserved SSD! 0378-4371(95)00450-5

Condensed Matter Physics, 2019

Isothermal-isobaric molecular dynamics simulations are used to examine the microscopic structure and some properties of water-methanol liquid mixture. The TIP4P/2005 and SPC/E water models are combined with the united atom TraPPE and the all-atom force field model for methanol. Our principal focus is to evaluate the quality of predictions of different combinations of model force fields concerning the composition dependence of basic properties of this system. Specifically, we explored the composition effects on density, excess molar volume and excess entropy, as well as on the surface tension and static dielectric constant. In addition, the structural properties are described in terms of the coordination numbers and the average number of hydrogen bonds between molecules of constituent species. Finally, the composition dependence of self-diffusion coefficients of the species is evaluated. All theoretical predictions are tested with respect to experimental data.