# Computational domain discretization

In order to solve Maxwell's equations using the finite-difference time-domain method, the computational domain must be **discretized**.

The computational domain in FDTD++ is currently discretized using a Cartesian mesh with circulating electric and magnetic field components, known as the Yee cell^{[1]}. See the image to the lower right.

## Controlling the discretization

The **discretization** is controlled entirely by setting the domain disc simulation parameter in the parameters file.

As an example, in order to change the **discretization** spacings along $x$, $y$, and $z$ to 2 nm (from their default values of 1 nm), the following could be added to the parameters file:
```
```

```
```domain disc 2.0e-9

```
or explicitly set the
```

**discretization** along each direction:
```
```

```
```domain disc 2.0e-9 x
domain disc 2.0e-9 y
domain disc 2.0e-9 z

```
The latter case also demonstrates how one may modify the
```

**discretization** along directions non-uniformly.

## Notes and references

- ↑ K. S. Yee, "Numerical solution of initial boundary value problems involving Maxwell's equations in isotropic media," IEEE Trans. Antennas Propagat.
**14**, 302-307 (1966).