Slip behavior at ionic solid–fluid interfaces

Molecular dynamics simulation results showing that the slip behavior at the interface between an ionic solid and fluid depends on the crystal face exposed to the flowing fluid are presented. The boundary condition of fluid NaCl confined between charged octopolar (1 1 1) surfaces is ‘stick’, but, between neutral (1 0 0) NaCl surfaces is ‘slip’. Also direction dependent change from stick to slip boundary condition is observed for atomically flat, neutral dipolar (and atomically rough, neutral octopolar) (1 1 0) NaCl surfaces. Thus, by changing the surface orientation and/or its roughness, the boundary conditions at ionic solid–fluid interface can be changed from slip to stick.