Microscopic structure of liquid 1-1-1-2-tetrafluoroethane (R134a) from Monte Carlo simulation.

1-1-1-2-tetrafluoroethane (R134a) is one of the most commonly used refrigerants. Its thermophysical properties are important for evaluating the performance of refrigeration cycles. These can be obtained via computer simulation, with an insight into the microscopic structure of the liquid, which is not accessible to experiment. In this paper, vapour-liquid equilibrium properties of R134a and its liquid microscopic structure are investigated using coupled-decoupled configurational-bias Monte Carlo simulation in the Gibbs ensemble, with a recent potential [J. Phys. Chem. B 2009, 113, 178]. We find that the simulations agree well with the experimental data, except at the vicinity of the critical region. Liquid R134a packs like liquid argon, with a coordination number in the first solvation shell of 12 at 260 K. The nearest neighbours prefer to be localized in three different spaces around the central molecule, in such a manner that the dipole moments are in a parallel alignment. Analysis of the pair interaction energy shows clear association of R134a molecules, but no evidence for C-HF type hydrogen bonding is found. The above findings should be of relevance to a broad range of fluoroalkanes.

[1]  Ioannis Skarmoutsos,et al.  Local intermolecular structure and dynamics in binary supercritical solutions. A molecular dynamics simulation study of methane in carbon dioxide , 2006 .

[2]  A. Idrissi,et al.  Nearest neighbor assessments of spatial distribution in CO2 : A molecular dynamics analysis , 2007 .

[3]  Jeffrey J. Potoff,et al.  Critical point and phase behavior of the pure fluid and a Lennard-Jones mixture , 1998 .

[4]  P. Jedlovszky.  Structural study of liquid methylene chloride with reverse Monte Carlo simulation , 1997 .

[5]  M. Mezei,et al.  Computer simulation study of liquid CH2F2 with a new effective pair potential model , 1999 .

[6]  Mark T. Oakley,et al.  Additive and nonadditive models of vapor-liquid equilibrium in CO2 from first principles. , 2009, The Journal of chemical physics.

[7]  Berend Smit,et al.  Computer simulations of vapor-liquid phase equilibria of n-alkanes , 1995 .

[8]  Yang Zhang,et al.  Dielectric constant and density dependence of the structure of supercritical carbon dioxide using a new modified empirical potential model: a Monte Carlo simulation study. , 2005, The journal of physical chemistry. B.

[9]  V. Vacek,et al.  Vapor-liquid equilibria of alternative refrigerants and their binaries by molecular simulations employing the reaction Gibbs ensemble Monte Carlo method , 2004 .

[10]  Mark T. Oakley,et al.  First principles models of the interactions of methane and carbon dioxide , 2010 .

[11]  Hans Hasse,et al.  A set of molecular models for carbon monoxide and halogenated hydrocarbons , 2003 .

[12]  Hans Hasse,et al.  Molecular models for 267 binary mixtures validated by vapor–liquid equilibria: A systematic approach , 2009 .

[13]  V. Vacek,et al.  Effective potentials for liquid simulation of the alternative refrigerants HFC-134a (CF3CH2F) and HFC-125 (CF3CHF2) , 1997 .

[14]  A. Panagiotopoulos.  Direct determination of phase coexistence properties of fluids by Monte Carlo simulation in a new ensemble , 1987 .

[15]  William L. Jorgensen,et al.  Monte Carlo simulations of liquid acetonitrile with a three-site model , 1988 .

[16]  Maurizio Fermeglia,et al.  Development of an all-atoms force field from ab initio calculations for alternative refrigerants , 2003 .

[17]  Ganesh Kamath,et al.  All-atom force field for the prediction of vapor-liquid equilibria and interfacial properties of HFA134a. , 2009, The journal of physical chemistry. B.

[18]  Zhenhao Duan,et al.  An optimized molecular potential for carbon dioxide. , 2005, The Journal of chemical physics.

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

[20]  Berend Smit,et al.  Understanding molecular simulation: from algorithms to applications , 1996 .

[21]  T. Straatsma,et al.  THE MISSING TERM IN EFFECTIVE PAIR POTENTIALS , 1987 .

[22]  David A. Kofke,et al.  Gibbs-Duhem integration: a new method for direct evaluation of phase coexistence by molecular simulation , 1993 .

[23]  J. Fischer,et al.  Vapour liquid equilibria of mixtures from the NpT plus test particle method , 1995 .

[24]  P. Jedlovszky,et al.  Role of the C−H···O Hydrogen Bonds in Liquids: A Monte Carlo Simulation Study of Liquid Formic Acid Using a Newly Developed Pair-Potential , 1997 .

[25]  Jonathan D Hirst,et al.  Gibbs ensemble Monte Carlo simulations of binary mixtures of methane, difluoromethane, and carbon dioxide. , 2010, The journal of physical chemistry. B.

[26]  V. Vacek,et al.  Vapor–Liquid Equilibria of Alternative Refrigerants by Molecular Dynamics Simulations , 1999 .

[27]  J. Ilja Siepmann,et al.  Novel Configurational-Bias Monte Carlo Method for Branched Molecules. Transferable Potentials for Phase Equilibria. 2. United-Atom Description of Branched Alkanes , 1999 .

[28]  D. Frenkel,et al.  Computer simulations in the Gibbs ensemble , 1989 .

[29]  S. D. da Rocha,et al.  The ester group: how hydrofluoroalkane-philic is it? , 2007, Langmuir.

[30]  P. Jedlovszky,et al.  Local order in some aprotic dipolar liquids , 1996 .

[31]  P. Jedlovszky,et al.  Monte carlo simulation of liquid acetone with a polarizable molecular model , 1995 .

[32]  S. D. da Rocha,et al.  Surfactant design for the 1,1,1,2-tetrafluoroethane-water interface: ab initio calculations and in situ high-pressure tensiometry. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[33]  Kwong H. Yung,et al.  Carbon Dioxide's Liquid-Vapor Coexistence Curve And Critical Properties as Predicted by a Simple Molecular Model , 1995 .

[34]  S. Klein,et al.  NIST Standard Reference Database 23: NIST Thermodynamic and Transport Properties of Refrigerants and Refrigerant Mixtures-REFPROP, Version 6.0 | NIST , 1998 .