A scalar quantity used to represent the thermodynamic state of a system.
| Name | Symbol | Formula | Natural variables |
|---|---|---|---|
| Internal energy | {\displaystyle \int (T{\text{d}}S-p{\text{d}}V+\sum _{i}\mu _{i}{\text{d}}N_{i})} | {\displaystyle S,V,\{N_{i}\}} | |
| Helmholtz free energy |
{\displaystyle U-TS} | {\displaystyle T,V,\{N_{i}\}} | |
| Enthalpy |
{\displaystyle U+pV} | {\displaystyle S,p,\{N_{i}\}} | |
| Gibbs free energy | {\displaystyle U+pV-TS}U+pV-TS | {\displaystyle T,p,\{N_{i}\}} | |
| Landau Potential (Grand potential) | U - T S -{\displaystyle \sum _{i}\,} \mu_i N_i | {\displaystyle T,V,\{\mu _{i}\}} |
