ChemPhysChem 2015-01-12

Two different models to predict ionic-liquid diffraction patterns: fixed-charge versus polarizable potentials.

Marco Campetella, Lorenzo Gontrani, Francesca Leonelli, Luigi Bencivenni, Ruggero Caminiti

Index: ChemPhysChem 16(1) , 197-203, (2015)

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Abstract

This study reports the performance of classical molecular dynamics (MD) in predicting the X-ray diffraction patterns of butylammonium nitrate (BAN) and two derivatives, 4-hydroxybutan-1-ammonium nitrate (4-HOBAN) and 4-methoxybutan-1-ammonium nitrate (4-MeOBAN). The structure functions and radial distribution functions obtained from energy-dispersive X-ray diffraction spectra, recorded newly for BAN and for the first time for 4-MeOBAN and 4-HOBAN, are compared with the corresponding quantities calculated from MD trajectories, to access information on the morphology of these liquids. The different behavior of two force fields, a polarizable multipole force field and a fixed-charge one supplemented by an explicit three-body term, is shown. The three-body force field proves to be superior in reproducing the intermediate q range, for which the polarizable force field gives the wrong peak position and intensities. In addition, both models can correctly account for the presence or absence of a low q peak in the scattering patterns. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.