Reference interaction site model and molecular dynamics study of structure and thermodynamics of methanol (original) (raw)
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Molecular dynamics simulations of water-methanol mixtures
Chemical Physics, 1991
Molecular dynamics simulations of two water-methanol mixtures with methanol mole fractions of 0.1 and 0.9 at room temperature have been performed. The interaction potentials are based on flexible three-site models for water and methanol. The structural changes relative to the pure solvents are demonstrated with the help of radial distribution functions and the geometrical arrangement of nearest-neighbor molecules. Differences in thermodynamic properties and in hydrogen bonding between the two mixtures and relative to the pure liquids are discussed. 0301-0104/91/% 03.50 0 1991 Elsevier Science Publishers B.V. All rights reserved.
Association effects in pure methanol via Monte Carlo simulations. I. Structure
The Journal of Chemical Physics, 2013
A methodology for the determination of the oligomers residing in a pure associated fluid was developed in the framework of the molecular simulation technique. Firstly, the number of hydrogen bonds between each pair of molecules of the fluid is computed by using a specific criterion to define the hydrogen bonding formation. Secondly, sets of molecules linked by hydrogen bonds are identified and classified as linear chains, cyclic aggregates, branched linear chains, branched cyclic aggregates and the rest of clustering. The procedure is applied over all the configurations produced in usual Monte Carlo simulations and allows the computation of the following properties characterizing the structure of the fluid: the fraction of molecules in the monomer or associated state, the fraction of each type of aggregate with a given size (and of molecules belonging to them), and the most probable and the average cluster size for each type. In addition, the degree of branching in branched linear chains and the type of ring in branched cyclic clusters can be obtained. In this work, all these quantities were computed for OPLS methanol using NpT Monte Carlo simulations at atmospheric pressure for 298.15 K (room conditions) and from 800 K to 350 K (gas phase), and along several supercritical isobars: 25, 50, 100, 200, and 500 MPa from 250 K to 1000 K. An analysis of the results has provided a comprehensive structural picture of methanol over the whole thermodynamic state space.
Molecular dynamics simulations of the properties of water-methanol mixtures. Effects of force fields
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.
A comparative Molecular Dynamics study of water–methanol and acetone–methanol mixtures
Journal of Molecular Liquids, 2011
Two binary mixtures with methanol as common component, namely water–methanol and methanol–acetone are studied by Molecular Dynamics simulations. Thermodynamical properties such as enthalpies, excess enthalpies, volumes and excess volumes are compared. Structural properties are studied through the various site–site pair correlation functions and the associated Kirkwood–Buff integrals. While the thermodynamical properties are relatively well calculated, we show that structural properties
Calculation of Physical Properties of the Methanol-Water Mixture Using Molecular Dynamics Simulation
In this study some properties of the methanol-water mixture such as diffusivity, density, viscosity, and hydrogen bonding were calculated at different temperatures and atmospheric pressure using molecular dynamics simulations (MDS). The results were compared with the available experimental data as well as some theoretical models; overall indicating a good agreement. This shows the useful and effective application of MDS for determination of physical properties.
Monte Carlo simulation of the binary liquid mixture water—methanol
Journal of Molecular Structure: THEOCHEM, 1993
Monte Carlo statistical mechanics simulations of water-methanol mixtures were performed in the isothermalisobaric ensemble (NPT) at T = 298 K andp = 1 .O atm; canonical ensemble (NVT) simulations were performed at this same temperature and experimental densities. Configurational averages were obtained by using Metropolis importance sampling and truncated octahedron box boundary conditions. To calculate the intermolecular energy, the TIP4P and a tree-site model with united atom representation for the methyl group were used for water and methanol molecules respectively. The potential energy surface for water-methanol interaction was calculated using combining rules and the original potential parameters for the pure liquids. Volume contraction and exothermic mixing were obtained in the present calculation, in fair agreement with experimental results. The radial distribution functions obtained show features indicating a large population of hydrogen bonded complexes. The analysis of site-site coordination numbers shows an enhancement of the average number of hydrogen bonded complexes at a methanol composition near 25%. This result agrees with the experimental observation that the water-methanol system has its largest deviation from the ideal mixture behavior at this same composition.
The Journal of Chemical Physics, 2013
Mixtures containing associated substances show a singular thermodynamic behaviour that has attracted to scientific community during the last century. Particularly, binary systems composed by an associating fluid and an inert solvent, where association occurs only between molecules of the same kind, have been extensively studied. A number of theoretical approaches were used in order to gain insights into the effect of the association on the macroscopic behaviour, especially on the second-order thermodynamic derivatives (or response functions). Curiously, to our knowledge, molecular simulations have not been used to that end despite describing the molecules and their interactions in a more complete and realistic way than theoretical models. With this in mind, a simple methodology developed in the framework of Monte Carlo molecular simulation is used in this work to quantify the association contribution to a wide set of thermodynamic properties for the {methanol + Lennard Jones} specific system under room conditions and throughout the composition range. Special attention was paid to the response functions and their respective excess properties, for which a detailed comparison with selected previous works in the field has been established.