Noura Dawass

5.2. M ETHODS 5 99 3. The value of Λ αα is identical in the ternary and pseudo-binary systems. Use Λ αα in Eq. (5.27) to compute MS diffusion coefficient of the pseudo- binary mixture. 4. In Eq. (5.27) , molecular weights ( M α and M β ) of the pseudo-binarymixture are essential. M β is the average molecular weight of the indistinguishable molecule, computed from: M β = N θ M θ + N γ M γ N θ + N γ (5.28) In the case of a 1:1 salt solution we have N γ = N θ so therefore M β = M θ + M γ 2 (5.29) 5. For pseudo-binary mixtures, the mole fractions required in Eq. (5.27) can be computed using: x α = N α N α + N θ + N γ and x β = 1 − x α (5.30) 5.2.3. F ORCE FIELD ChCl and urea molecules were modelled using the general amber force field (GAFF [155] . Partial charges were derived using the Restrained Electrostatic Potential (RESP) method based on the Hartree-Fock HF/6.31G* level of the- ory [147, 156, 157] . As discussed in the earlier works by Perkins et al. [147, 158] , Liu et al. [159] , Shah and Mjalli [160] , and Chaban et al. [161] , charge scaling is essential when simulating ILs and DESs due to overestimated electrostatic interaction potentials. Blazquez and co-workers [162] have shown that even for simple electrolytes such as NaCl, charge scaling improves electrostatic in- teractions. We scaled down the partial charges of ChCl molecules by a fac- tor of 0.8. The GAFF force field combined with reduced charges have been used in MD studies to accurately predict structural, thermodynamic and trans- port properties of many ChCl-based DESs such as reline, ethaline and glyce- line [143, 144, 147, 158, 160, 163, 164] . All force field parameters used in this chapter are listed in the Supporting Information of Ref. [131] . 5.2.4. S IMULATION DETAILS MD simulations were performed using the Large-Scale Atomic/Molecular Mas- sively Parallel Simulator (LAMMPS) version released on August, 2018 [127] . Eight different mole fractions of urea ranging from 0.20 to 0.71 were considered. For