Glossary
Gibbs Energy
The Gibbs energy is a thermodynamic function of state defined by
G = H - T·S
where H is the enthalpy (Joules), T is the absolute temperature (Kelvins), and S is the entropy (Joules per Kelvin).
Once the Gibbs energy is known, all other thermodynamic properties can be derived. For example:
• Entropy: S = - (∂G/∂T)P,n
• Enthalpy: H = G - T·(∂G/∂T)P,n
• Helmholtz energy: A = G - P·(∂G/∂P)T,n
• Internal energy: U = G - T·(∂G/∂T)P,n - P·(∂G/∂P)T,n
• Volume: V = (∂G/∂P)T,n
• Heat capacity at constant pressure: CP = - T·(∂2G/∂T2)P,n
• Chemical potential (partial Gibbs energy): μ = (∂G/∂n)T,P
• Thermal expansion: α = V-1·(∂2G/∂T∂P)n
• Isothermal compressibility: κ = - V-1·(∂2G/∂P2)T,n
• Bulk modulus: B = 1/κ