Parmar SM, Depew DD, Wirz RE, Vaghjiani GL. Structural Properties of HEHN- and HAN-Based Ionic Liquid Mixtures: A Polarizable Molecular Dynamics Study.
J Phys Chem B 2023;
127:8616-8633. [PMID:
37776252 DOI:
10.1021/acs.jpcb.3c02649]
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Abstract
Molecular dynamics simulations of binary mixtures comprising 2-hydroxyethylhydrazinium nitrate (HEHN) and hydroxylammonium nitrate (HAN) were conducted using the polarizable APPLE&P force field to investigate fundamental properties of multimode propulsion (MMP) propellants. Calculated densities as a function of temperature were in good agreement with experiments and similar simulations. The structural properties of neat HEHN and HAN-HEHN provided insights into their inherent, protic nature. Radial distribution functions (RDFs) identified key hydrogen bonding sites located at N-H···O and O-H···O within a first solvation shell of approximately 2 Å. Angular distribution functions further affirmed the relatively strong nature of the hydrogen bonds with nearly linear directionality. The increased hydroxylammonium cation (HA+) mole fraction shows the influence of competitively strong hydrogen bonds on the overall hydrogen bond network. Dominant spatial motifs via three-dimensional distribution functions along with nearly nanosecond-long hydrogen bond lifetimes highlight the local bonding environment that may precede proton transfer reactions.
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