# Modifying the Integral Equation Method

When using the MLFMM, you can specify the integral equation to obtain faster iterative convergence.

1. If the model will be solved using the multilevel fast multipole method (MLFMM) activate the MLFMM.
2. Select the face(s) of the enclosed volume in the in the 3D view or in the details tree.
3. In the details tree, from the right-click context menu, select Properties.
4. On the Modify Face dialog, click the Solution tab.
5. From the Integral equation drop-down list, select one of the following options.
• Combined field

Solve the model using a combination of the electric field integral equation (EFIE) and magnetic field integral equation (MFIE). This is known as the combined field integral equation (CFIE).

• Electric field
Solve the model using the electric field integral equation (EFIE).
• Magnetic field
Solve the model using the magnetic field integral equation (MFIE).
Note: The electric field integral equation (EFIE) is the default and is valid for all geometries (open, fully enclosed, metallic and dielectric).
6. Click OK to save the face properties and to close the dialog.