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Mie Potentials for Phase Equilibria: Application to Alkenes

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journal contribution
posted on 09.10.2014, 00:00 by Jeffrey J. Potoff, Ganesh Kamath
Transferable united-atom force fields based on Mie potentials are presented for alkenes. Monte Carlo simulations in the grand canonical ensemble, combined with histogram reweighting, are used to determine vapor–liquid coexistence curves, vapor pressures, heats of vaporization, boiling points, and critical properties for 1-alkenes from ethene to 1-octene. To assess the transferability of the optimized parameters, additional calculations are performed for the cis and trans isomers of 2-butene and 2-pentene and the dienes 1,3-butadiene and 1,5-hexadiene. Saturated liquid densities for the 1-alkenes, 2-pentenes, and 1,5-hexadiene are predicted to within 1 % of experimental data, while deviations of (2 to 5) % from experiment were observed for cis-2-butene and 1,3-butadiene, respectively. Vapor pressures for the alkenes are predicted to within (2 to 15) % of experiment, with errors increasing with chain length and at lower temperatures. Critical temperatures are predicted to within 1 % of experiment for all molecules except for 1,3-butadiene, where the critical temperature is under-predicted by 3.5 %. Transferability is further evaluated through calculations of binary mixture vapor–liquid equilibria. Predictions of the Mie potentials for ethane + propene and 1-butane + 1-hexene are indistinguishable from experimental data.