title: Molecular dynamics simulation of the energetic room-temperature ionic liquid, 1-hydroxyethyl-4-amino-1,2,4-triazolium nitrate (HEATN).
abstract: Molecular dynamics (MD) simulations have been performed to investigate the structure and dynamics of an energetic ionic liquid, 1-hydroxyethyl-4-amino-1,2,4-triazolium nitrate (HEATN). The generalized amber force field (GAFF) was used, and an electronically polarizable model was further developed in the spirit of our previous work (Yan, T.; Burnham, C. J.; Del Popolo, M. G.; Voth, G. A. J. Phys. Chem. B 2004, 108, 11877). In the process of simulated annealing from a liquid state at 475 K down to a glassy state at 175 K, the MD simulations identify a glass-transition temperature region at around 250-275 K, in agreement with experiment. The self-intermediate scattering functions show vanishing boson peaks in the supercooled region, indicating that HEATN may be a fragile glass former. The coupling/decoupling of translational and reorientational ion motion is also discussed, and various other physical properties of the liquid state are intensively studied at 400 K. A complex hydrogen bond network was revealed with the calculation of partial radial distribution functions. When compared to the similarly sized 1-ethyl-4-methyl-1,4-imidazolium nitrate ionic liquid, EMIM+/NO3-, a hydrogen bond network directly resulting in the poorer packing efficiency of ions is observed, which is responsible for the lower melting/glass-transition point. The structural properties of the liquid/vacuum interface shows that there is vanishing layering at the interface, in accordance with the poor ion packing. The effects of electronic polarization on the self-diffusion, viscosity, and surface tension of HEATN are found to be significant, in agreement with an earlier study on EMIM+/NO3- (Yan, T.; Burnham, C. J.; Del Popolo, M. G.; Voth, G. A. J. Phys. Chem. B 2004, 108, 11877).
authors.affiliation: Center for Biophysical Modeling and Simulation and Department of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.forename: Tianying
authors.initials: T
authors.lastname: Yan
authors.forename: Yanting
authors.initials: Y
authors.lastname: Wang
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Voth
mesh_terms: D003198:Computer Simulation; D005898:Glass / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009566:Nitrates / Q000737:chemistry*; D013696:Temperature; D014230:Triazoles / Q000737:chemistry*
chemical_list: C528284:1-hydroxyethyl-4-amino-1,2,4-triazolium nitrate; D052578:Ionic Liquids; D009566:Nitrates; D014230:Triazoles