# List of material parameters

A list of material parameters that the user can define is provided below, in bold, along with a brief description.

## Contents

## Dielectric material

In FDTD++, a **dielectric material** is defined in the materials file in the main materials block:
```
```

```
```material n
{
epsr #
}

```
where
```

**#** is the relative permittivity.

## Conductor

In FDTD++, a **conductor** is defined in the materials file by providing $\sigma$ in a **conductor** block^{[1]}:
```
```

```
```conductor
{
sigma #
}

```
where
```

**#** is the value of $\sigma$. Note that `conductor`

, `{`

, and `}`

should each be on their own lines.

## Perfect electric conductor

In FDTD++, a **PEC** is defined in the materials file by declaring a **PEC** block^{[2]}:
```
```

```
```PEC
{
}

```
Note that
```

`PEC`

, `{`

, and `}`

should each be on their own lines. Note also that a **PEC** block should not be defined in combination with any other models, otherwise the simulation will stop and report an error.

## Drude model

In FDTD++, a **Drude model** is defined in the materials file by providing $\omega_p$ and $\gamma$ in a **Drude** block:
```
```

```
```Drude
{
omegap #1
gamma #2
}

```
where
```

**#1** and **#2** are the values of $\omega_p$ and $\gamma$ (both in eV), respectively. Note that `Drude`

, `{`

, and `}`

should each be on their own lines.

## Hydrodynamic Drude model

The **hydrodynamic Drude model** is currently only implemented in the research version of FDTD++, but will be available in future releases of FDTD++. In the meantime, see the work by J. M. McMahon et al.^{[3]}^{[4]}

## Lorentz oscillator model

In FDTD++, a **Lorentz oscillator model** is defined in the materials file by providing $\Delta \varepsilon_p$, $\omega_p$, and $\delta$ In a **Lorentz** block^{[5]}:
```
```

```
```Lorentz
{
depsr #1
omegap #2
delta #3
}

```
where
```

**#1**, **#2**, and **#3** are the values of $\Delta \varepsilon_p$ (unitless), $\omega_p$ (in eV), and $\delta$ (in eV), respectively. Note that `Lorentz`

, `{`

, and `}`

should each be on their own lines.

## Debye model

In FDTD++, a **Debye model** is defined in the materials file by providing $\omega_p$ and $\gamma$ in a **Debye** block:
```
```

```
```Debye
{
depsr #1
tau #2
}

```
where
```

**#1** and **#2** are the values of $\Delta \varepsilon$ (unitless) and $\tau$ (both in s$^{-1}$), respectively. Note that `Debye`

, `{`

, and `}`

should each be on their own lines.

## Combining models

## Notes and references

- ↑ The
**conductor**model is only available in the full version of FDTD++. See here. - ↑ The
**perfect electric conductor**model is only available in the full version of FDTD++. See here. - ↑ J. M. McMahon, S. K. Gray, and G. C. Schatz, "Nonlocal Optical Response of Metal Nanostructures with Arbitrary Shape,"
*Phys. Rev. Lett.***103**, 097403 (2009). - ↑ J. M. McMahon, S. K. Gray, and G. C. Schatz, "Calculating nonlocal optical properties of structures with arbitrary shape,"
*Phys. Rev. B***82**, 035423 (2010). - ↑ The
**Lorentz oscillator model**is only available in the full version of FDTD++. See here.