title: Temperature-dependent structure of ionic liquids: X-ray scattering and simulations.
abstract: In this article we determine the temperature-dependent structure of the tetradecyltrihexylphosphonium bis(trifluoromethylsulfonyl)amide ionic liquid using a combination of X-ray scattering and molecular dynamics simulations. As in many other room-temperature ionic liquids three characteristic intermolecular peaks can be detected in the structure function S(q). A prepeak or first sharp diffraction peak is observed at about q = 0.42 A(-1). Long range anion-anion correlations are the most important contributors to this peak. In all systems we have studied to date, this prepeak is a signature of solvation asymmetry. The peak in S(q) near q = 0.75 A(-1) is the signature of ionic alternation and arises from the charge ordered separation of ions of the same charge. The most intense diffraction peak near q = 1.37 A(-1) arises from short-range separation between ions of opposite charge combined with a significant contribution from cationic carbon-carbon interactions, indicating that cationic hydrophobic tails have significant contacts.
authors.affiliation: Department of Chemistry, University of Iowa, Iowa City, IA, 52242-1294, USA.
authors.forename: Hemant K
authors.initials: HK
authors.lastname: Kashyap
authors.forename: Cherry S
authors.initials: CS
authors.lastname: Santos
authors.forename: Harsha V R
authors.initials: HV
authors.lastname: Annapureddy
authors.forename: N Sanjeeva
authors.initials: NS
authors.lastname: Murthy
authors.forename: Claudio J
authors.initials: CJ
authors.lastname: Margulis
authors.forename: Edward W
authors.initials: EW
authors.lastname: Castner
mesh_terms: D018360:Crystallography, X-Ray; D052578:Ionic Liquids / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D013696:Temperature
chemical_list: D052578:Ionic Liquids