Electrolytes respond to contact with a charged solid surface (metal electrode, semiconductor or insulating ionic solids) by formation of an electric double layer. The modelling of electric double layers at an atomistic level remains a major challenge. A well known technical problem is of course how to fit models of electric double layers in the periodic cells commonly used in atomistic simulation. However, there remain even open questions of a more fundamental nature. This concerns in particular the microscopic definition of the electrostatic potential across an electric double layer (the Galvani potential of electrochemistry) which continues to be an elusive quantity. In this talk we will approach these questions from the point of view of dielectrics. We will argue that focusing on electric fields and polarization rather than on potentials and charges has technical as well as conceptual advantages. As examples we will discuss classical force fields results for homogeneous electrolytic solutions, an interface with a wall with fixed charge and a polar surface (NaCL(111)). This work is in collaboration with Chao Zhang (now in Uppsala university), Thomas Sayer and Stephen Cox.
 Chao Zhang and Michiel Sprik, Phys. Rev. B 94 (2016), 245309.
 Thomas Sayer, Chao Zhang, Michiel Sprik, J. Chem. Phys. 147 (2017) 104702.