MedeA-GIBBS
Scope
MedeA-GIBBS offers state-of-the-art computational capabilities to predict
thermodynamic properties such as adsorption isotherms of gas mixtures in
nanoporous materials, vapor pressures of pure compounds and mixtures,
Joule-Thomson coefficients, and the phase behavior under high pressure and
temperature. Combined with comprehensive structural databases such as the
Inorganic Crystal Structure Data (ICSD) database and advanced quantum mechanical
methods such as VASP and Phonon capabilities, which are an integral part of
Materials Design's technology platform MedeA, the GIBBS module expands MedeA's
capabilities into the realm of thermophysical properties of fluids and
fluid/solid interfaces. These capabilities are of particular importance in the
domain of nanomaterials, where complex topologies can lead to novel and
unexpected behavior. MedeA-GIBBS allows exploring the thermodynamic and entropic
consequences in such systems, thus providing a sound basis for the
interpretation of experiments and the design of novel materials.
The GIBBS program is the result of a major ongoing joint research effort by the
group of Prof. Alain Fuchs (CNRS and University of Paris, France) and the
Institut Français du Pétrole. GIBBS represents a state-of-the-the-art
implementation of the Gibbs ensemble Monte Carlo method and related approaches
and features a number of innovative and advanced capabilities.
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Capabilities
Systems and Statistical Ensembles
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Thermophysical properties of single phase, multicomponent systems
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Calculation of equilibria of two-phase liquid-gas, liquid-liquid or
multiphase liquid-liquid-gas systems for constant volume or constant
pressure
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Adsorption isotherms in nanoporous structures by representing the steric
and electrostatic interactions with the solid phase in the form of a
three-dimensional grid
Types of Molecules
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Rigid molecules, with or without charges
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Flexible linear, branched, and monocyclic molecules without charges,
e.g. alkanes and isoalkanes
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Semi-flexible molecules, e.g. olefins
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Semi-flexible molecules with charges, e.g. alcohols, mercaptanes,
thioethers
Types of Potentials
Types of Interaction Energies
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Dispersion-repulsion (Lennard-Jones centers) with cut-off and
long-distance correction
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Mixing rules according to Lorentz-Berthelot, Kong, and Waldmann-Hagler
for the evaluation of cross-terms
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Electrostatic energies with cut-off distance
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Ewald summation
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Polarization of Lennard-Jones centers
Types of Monte-Carlo Moves
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Translation of single molecules or all molecules - all statistical
ensembles
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Rotation of single molecules or all molecules - all ensembles
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Partial re-growth of flexible molecules - all ensembles
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Rotation of one center around centers of nearest-neighbors for flexible
molecules - all ensembles
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Volume changes for all molecules - single-phase NPT and Gibbs ensembles
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Transfer between phases, all molecules - Gibbs ensemble
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Reptation for linear molecules - all ensembles
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Pivoting
Application example
Separation processes are of critical importance in the chemical and
petrochemical industry. In this context, zeolites play a prominent role. Given
the wide compositional
and structural richness of this class of materials, the selection and
optimization of the best materials is a challenging problem. Simulations can
help in this process, thus gaining focus and time. As an illustrative example of
the use of GIBBS, this application shows the separation of paraxylene from
metaxylene by adsorption in NaY, KY, BaX and NaX faujasites (Eluxyl process).
The adsorption isotherms are computed using the GIBBS approach. The
characteristic behavior of each zeolite is correctly predicted [6], thus
demonstrating the viability of the present computational method.
References
1. A. Boutin, A. H. Fuchs, and P. Ungerer,
"New optimization method for
intermolecular potentials - Optimization of a new anisotropic united atoms
potential for olefins - Prediction of equilibrium properties", J. Chem. Phys
118, 3020 (2003)
2. E. Bourasseau, P. Ungerer, and A. Boutin,
"Prediction of Equilibrium
properties of cyclic alkanes by Monte Carlo simulation - new anisotropic
united atoms potential - new transfer bias method", J. Phys. Chem. B 106,
5483 (2002)
3. V. Lachet, S. Buttefey, A. Boutin, and A. H. Fuchs,
"Molecular
simulation of adsorption equilibria of xylene isomer mixtures in faujasite
zeolites. A study of cation exchange effect on adsorption selectivity",
Phys. Chem. Chem. Phys. 3, 80-8 (2001)
4. J. Delhommelle, C. Tschirwitz, P. Ungerer, G. Granucci, P. Millié, D.
Pattou, and A. H. Fuchs, "Derivation of an optimized potential model for
phase equilibria (OPPE) for sulfides and thiols", Journal of Physical
Chemistry B 104, 4745 (2000)
5. B. Neubauer, B. Tavitian, A. Boutin, and P. Ungerer,
"Molecular
simulations on volumetric properties of natural gas", Fluid Phase Equilibria
161, 45 (1999)
6. V. Lachet, A. Boutin, B. Tavitian, and A. H. Fuchs, Langmuir 15, 8678
(1999)
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