The Transition Boundary Condition is used on interior boundaries to model a sheet of a highly conducting medium with a thickness relatively smaller than the characteristic size, and curvature, of the objects being modeled. It can be used even if the thickness is many times greater than the skin depth. Accounting for the material properties as well as the thickness of the sheet, transfer and surface impedances are used to relate the current flowing on the surface of either side to the discontinuity in the tangential electric field. Mathematically it is described by a relation between the electric field discontinuity and the induced surface current density:

Where indices 1 and 2 refer to the different sides of the layer. See Ref. 7 for more details.

The Transition Boundary Condition section has the following material properties for the thin layer, which this boundary condition approximates:

The defaults use the values From material, taking the properties from the material specified for the boundary. For User defined, enter different values or expressions.