News

Yong's paper on in silico prediction of melting points appears in JCTC

Yong's paper entitled "Toward Fully in Silico Melting Point Prediction Using Molecular Simulations" just appeared in the Journal of Chemical Theory and Computation (2013, 9(3), 1592-1599). In this paper, he shows how crystal structure prediction methods can be combined with the "pseudosupercritical path sampling" approach for determining the free energy between crystalline and liquid phases to predict melting points with no recourse to experimental data. The method is applied to two test molecules 2-propenal and 4-cyanopyridine N-oxide. The method works well for these molecules, even if the predictd crystal structures do not math the experimental ones. Thsi is due to the closeness in free energies of the predicted and actual crystal structures. The method did not work well for it was applied to the more complex molecule6-amino-2-(phenylsulfonylimino)-1,2-dihydrophridine. We suspect this is due to limitations on the force field. This is exciting work, and we hope it can be generalized to many more compounds.


New Papers by Andrew, Jindal, and Yong

Yong Zhang published a paper entitled "The Effect of C2 Substitution on Melting Points and Liquid Phase Dynamics of Imidazolium-Based Ionic Liquids: Insights from Molecular Dynamics Simulations”, inPhysical Chemistry Chemical Physics, 2012, 14(35), 12157-12164. In it, he provided detailed evidence that entropic effects play a big role in determining the melting point and viscosity trends observed when the C2 carbon of imidazolium-based ionic liquids is methylated.

The origin of higher melting points of C2 methylated alkyl-imidazolium PF6 ionic liquids is mainly entropic.

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Andrew Paluch, Cameron Vitter and Jindal Shah published a paper entitled“A Comparison of the Solvation Thermodynamics of Amino Acid Analogues in Water, 1-Octanol and 1-n-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide Ionic Liquids by Molecular Simulation”, inJournal of Chemical Physics, 2012, 137, 184505. They developed a "hydrophobicity scale" and showed how expanded ensemble simulations can be used to quantitatively estimate the solvation thermodynamics of amino acid analogues in various solvents, including ionic liquids.


A comparison of the dimensionless molar entropy of transfer between solvent A and water, and lnK* computed at 328 K via molecular simulation. Solvent A corresponds to either 1-octanol, [emim]+ [Tf2 N]− , [bmim]+ [Tf2 N]− , [omim]+ [Tf2 N]− , or p-octanol, as indicated by the leg- end.

Edward Maginn 2014ed@nd.edu