The structure of water-methanol mixtures under an electric field: Ab initio molecular dynamics simulations

- Electric field affects hydrogen bonded network in water-methanol mixtures.
- Hydrogen bonded network is dominated by the hydrophobic alkyl group of methanol.
- A hollow channel is formed along the field direction in methanol-rich mixtures.
- This channel promotes proton transport, but is sensitive to density fluctuations.
- The mixtures are not ideally mixed at low methanol concentrations even at zero field.

Ab initio molecular dynamics simulations were employed to study the microstructure of water-methanol mixtures subject to external electric fields. The electric field has a complex effect on the hydrogen bond network in the mixtures. At low methanol concentrations the water molecules form a percolated network surrounding short chains of methanol molecules. At high concentrations the water and methanol molecules segregate forming two separate hydrogen bond networks. The application of the field affects the structural evolution of the hydrogen bond network and a surprising 'hollow channel' is formed in the methanol-rich mixtures when under moderate fields (∼0.50 V/Å).

250