# Boundaries of the study domain and reference potentials

## Boundaries of the study domain with IB

If the technique of the infinite box (IB) is used, then the boundary conditions are automatically assigned by Flux on the infinite box (the electric potential at infinity is a floating value).

## Boundaries of the study domain without IB

If the technique of the infinite box (IB) is not used, the boundary conditions on the border of the computation domain are set by the user by means of the regions known as non-material. The boundary conditions proposed are the following: normal electric field or tangential electric field.

In the absence of the boundary regions, the default boundary condition is applied. The electric field is tangent to the boundaries.

## Symmetries and periodicities

If symmetries are assigned to the study domain, the user should provide the type of the symmetries. The electric field can be tangent or normal on the symmetry planes defined in the geometry context.

If periodicities are assigned to the study domain, the user should provide the type of the periodicities. Cyclic or anti-cyclic conditions can be imposed on the periodicity planes defined in the geometry context.

## Reference electric potentials

In order that the electric potential VEL (in the electrolyte) may be completely defined, it is necessary to impose its value at least at one point (in the electrolyte).

If the problem has an electrochemical interface, the reference potential in the electrolyte is determined by the polarization law (see § Definition of a polarization law).

In order that the electric potential V (in the metallic structure) may be entirely defined, it is necessary to impose its value at least at one point (in the electrolyte).

In order to define a reference electric potential, it is necessary to create a specific region of the Imposed Potential type (with V = 0 V), and to assign it to a point of the electrolyte (for the reference of the electrolytic potential VEL) and/or to a point of the metallic structure (for the reference of metallic potential V).