  A modeling of metasurfaces in the finite element method (FEM) based on
generalized sheet transition conditions (GSTCs) is presented. The
discontinuities in electromagnetic fields across a metasurface as represented
by the GSTC are modeled by assigning nodes to both sides of the metasurface.
The FEM-GSTC formulation in both 1D and 2D domains is derived and implemented.
The method is extended to handle more general bianistroptic metasurfaces. The
formulations are validated by several illustrative examples.
