In the ferroelectric literature, thermodynamic potentials are often written in terms of electric polarization P rather than displacement field D. When written in terms of D, the minimization of a thermo potential retains its equivalence to the entropy maximum principle, so there is a clear downside to using P. But aside from this, how does one construct the potentials with P? In the literature that I have found so far, it often looks like P is simply substituted for D, and the point is not explicitly discussed.(adsbygoogle = window.adsbygoogle || []).push({});

Secondly, according to the textbook by Lines and Glass, the other downside to using P in the thermodynamic potentials is that constant P conditions are not obtainable in practice. I am having trouble seeing how one obtains constant E or constant D conditions experimentally. The book makes some reference to open circuit conditions being constant D and short circuit being constant E. For short circuit, the field in the ferroelectric should be zero, and thus constant. Is it possible to obtain constant E conditions for E=\=0? For open circuit, I don't see how this corresponds to constant D at all.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Thermodynamics of ferroelectrics - D vs P

Can you offer guidance or do you also need help?

**Physics Forums | Science Articles, Homework Help, Discussion**