Insight into the structural and transport properties of methyl and benzyl triphenyl phosphonium based deep eutectic solvents using molecular dynamics simulations

Abstract

Molecular dynamics simulation of twelve phosphonium based DESs based on methyl triphenyl phosphonium bromide and benzyl triphenyl phosphonium chloride as hydrogen bond acceptors (HBA) with glycerol, ethylene glycol, triethylene glycol and trifluoroacetamide as hydrogen bond donors (HBDs) are carried out with the Generalized Amber Force Field between 25 °C and 95 °C at 1 atm pressure. Isobaric-isothermal ensemble is used for predicting the structural properties, namely, radial distribution function and coordination number. Further, time resolved trajectory data is correlated to predict the transport properties such as, self-diffusivity, binary-diffusivity, ionic conductivity and viscosity. The temperature dependence of predicted density is observed with 4.96 × 10−2 absolute average deviations from experimental dataset. Further, the self-diffusivities are predicted using Einstein's approach and ionic conductivity is calculated from Nernst-Einstein equation as well as Green-Kubo formulation. Further, the viscosity is also predicted using the Green-Kubo formulation. The predicted ionic conductivities and viscosities are fitted in the Vogel-Fulcher-Tammann (VFT) equation to calculate the VFT parameters for the respective DESs.