# Material Thermal Response
Editor: Model › Mediums · Python: td.SolidSpec, td.FluidSpec
In a Heat project, each medium has Thermal Properties. The solver computes the temperature only in structures whose medium is a solid (SolidSpec) with a Thermal conductivity. Structures with other mediums are left out. Optical Perturbation makes the optical properties of a medium depend on the temperature.
# Thermal Properties
New Medium form
- In a Heat project, a new medium starts with Medium Type SolidSpec and an empty Thermal conductivity, which is required.
- The unit is W/(µm·K): 1 W/(m·K) is 1e-6 W/(µm·K).
- For all fields, see Thermal Properties.
# Optical Perturbation
# How to Choose
| If the material … | Use the Medium Type … |
|---|---|
| Carries heat in the device, for example silicon, oxide or a metal | SolidSpec, with its Thermal conductivity |
| Is a gas or a liquid around the device, which you do not simulate | FluidSpec: no temperature is computed there |
# Common Mistakes
- A conductivity in W/(m·K). The editor uses W/(µm·K), so the value must be 1e-6 times smaller.
- No medium with thermal properties. The check then fails. See Heat Troubleshooting.