# List of material parameters

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

## 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.

## Notes and references

1. The conductor model is only available in the full version of FDTD++. See here.
2. The perfect electric conductor model is only available in the full version of FDTD++. See here.
3. 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).
4. 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).
5. The Lorentz oscillator model is only available in the full version of FDTD++. See here.