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# Perfect electric conductor (PEC) (1D FDTD)

A **perfect electric conductor (PEC)** has zero tangential electric field at its surface. FDTD OpenMP exposes a reflecting option named PEC, whose material setter removes boundary absorption:

```c
for (size_t k = 0; k < width; k++) {
    if (k > pec_width && k < width - pec_width)
        continue;
    material->fm_sigma_m[k] = 0.0;
    material->fm_sigma_e[k] = 0.0;
}
```

`pec_width` chooses where conductivity is cleared; it does not create a metallic slab or clamp both electric endpoints.

Termination comes from the kernel's loop bounds: `Ez[0]` and the last $H_y$ sample are not updated. They remain zero from initialization during ordinary stepping. The left endpoint therefore fixes an electric sample, while the right fixes a magnetic sample. The two ends are not symmetric PEC walls. When replacing a [[fdtd-openmp-pml|PML]], clear the region containing the losses that should be removed.

Source: [fdtd_ez_material.c](https://github.com/yanevskiv/fdtd-openmp/blob/main/src/fdtd/Ez/fdtd_ez_material.c).