# Integral Equation Methods (EFIE, MFIE and CFIE)

The relevant integral equation method can be used to solve a model to either obtain faster iterative or higher numerical accuracy when using the MoM or MLFMM.

When solving a structure that consists of perfectly conducting surfaces (PEC), the solution can be accelerated using either the electric field integral equation (EFIE) or the magnetic field integral equation (MFIE).

The EFIE method has a higher numerical accuracy and applicable to open structures, whereas the MFIE method has much faster iterative convergence and applicable to enclosed, perfectly conducting metallic regions.

To obtain both accuracy and faster iterative convergence for the solution using less
memory, the combined field integral equation (CFIE) method is used.

Note: The CFIE / MFIE is only
applicable to enclosed, perfectly conducting metallic regions.

When specifying the CFIE factor, you are
specifying if the solution must be one of the following:

- A pure EFIE solution (CFIE factor = 1)
- A pure MFIE solution (CFIE factor = 0)
- A combination of EFIE and MFIE, which is a CFIE solution (0 < CFIE factor < 1)

Note: The EFIE is the default solution in
Feko.