Theory 25/High-Pressure Physics
Transition Pressure Is a Modulus Ratio
The claim
The pressure at which a solid-solid transition occurs is set by the ratio of bulk modulus to volume change rather than by the enthalpy difference alone.
01The mechanism
Pressure drives transitions by doing work against the volume change; a stiff material with a small volume change needs a much higher pressure.
02Predictions
- P1Transition pressure should track the ratio.
- P2Enthalpy alone should mispredict.
03Refutation
Transition pressure tracking enthalpy would remove the modulus term.