title: Two different models to predict ionic-liquid diffraction patterns: fixed-charge versus polarizable potentials.
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.
authors.affiliation: Department of Chemistry, University "La Sapienza", Roma, Piazzale Aldo Moro 5, 00185 Roma (Italy).
authors.forename: Marco
authors.initials: M
authors.lastname: Campetella
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Gontrani
authors.forename: Francesca
authors.initials: F
authors.lastname: Leonelli
authors.forename: Luigi
authors.initials: L
authors.lastname: Bencivenni
authors.forename: Ruggero
authors.initials: R
authors.lastname: Caminiti
keywords: X-ray diffraction; ionic liquids; molecular dynamics; polarizable force field; three-body force field