(247k) Mie Potentials for Phase Equilibria: Application to Ethers and Sulfides

Potoff, J. J. - Presenter, Wayne State University
Barhaghi, M. - Presenter, Wayne State University

Optimization of non-bonded parameters in molecular mechanics force fields is a time consuming trial and error process.  Methodologies to predict optimized parameters for these models have been developed that use perturbation theory[1], or equations of state, such as SAFT[2, 3], which reduces significantly the range of parameter space that must be explored and the overall computational expense of the optimization.  This methodology has been shown to be effective for the development of coarse-grained models[2], and a united atom force field for n-alkanes[4].  Despite their success, however, the application of these methodologies to the development of complex, all-atom force fields that include electrostatic interactions is unclear. 

In this work, ab initio calculations are used to guide the development of optimized Mie potentials for ethers and sulfides.   Potential energy surfaces are determined for neon, argon and Na+ interacting with propane, dimethyl ether, diethyl ether, dimethyl sulfide, diethyl sulfide, methanol and ethanol at the MP2/aug-cc-PVTZ level.  These data are used to provide insight into the transferability of parameters for methyl and methylene groups when placed in different bonding environments, and to predict the relative contribution of each atom to the overall interaction energy.  These data are also used to predict the balance between dispersion and electrostatic interactions, and guide the choice of repulsion exponent. Parameters predicted from ab initio calculations are refined using grand canonical histogram reweighting Monte Carlo simulations [5-7].  The resulting models predict experimental liquid densities and vapor pressures to within 1% and 10%, respectively.

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3.         van Westen, T., T.J.H. Vlugt, and J. Gross, Determining Force Field Parameters Using a Physically Based Equation of State. Journal of Physical Chemistry B, 2011. 115(24): p. 7872-7880.

4.         Grosse, A.V., R.C. Wackher, and C.B. Linn, Physical properties of the alkyl fluorides and a comparison of the alkyl fluorides with the other alkyl halides and with the alkyls of the elements of period II. Journal of Physical Chemistry, 1940. 44(3): p. 275-296.

5.         Potoff, J.J. and D.A. Bernard-Brunel, Mie Potentials for Phase Equilibria Calculations: Application to Alkanes and Perfluoroalkanes. Journal of Physical Chemistry B, 2009. 113(44): p. 14725-14731.

6.         Potoff, J.J. and G. Kamath, Mie Potentials for Phase Equilibria: Application to Alkenes. Journal of Chemical and Engineering Data, 2014. 59(10): p. 3144-3150.

7.         http://gomc.eng.wayne.edu.