A Koenig Born diagram is a diagram used to remember the
Maxwell's relations.
In the
figure below , U stands for
Internal Energy, H for
Enthalpy, G for
Gibb's free energy, and A for the
Helmholtz free energy, V is
Volume, P is
pressure, T is
temperature and S is
entropy.
These are arranged in a Koenig Born diagram as follows:
V A T
U G
S H P
In addition there is an arrow from S to T and from P to V.
The diagram is read as follows. For example the top row of the square would be read as dA is a function of dV and dT and dA=-PdV-SdT.
The coefficient of dV is -P because the arrow links V to P and the connection goes against the arrow.Similarly the coefficent of dT is S because the arrow links T to S and the the minus sign is because the connection goes against the arrow.