Editing Phase rule (section)

==Phase rule at constant pressure==
For applications in [[materials science]] dealing with phase changes between different solid structures, pressure is often imagined to be constant (for example at 1 atmosphere), and is ignored as a degree of freedom, so the formula becomes:<ref>{{cite web |last1=Ehlers |first1=Ernest G. |title=Phase - State of Matter (section Binary Systems) |url=https://www.britannica.com/science/phase-state-of-matter |publisher=Encyclopedia Britannica |access-date=17 November 2022 |quote=at atmospheric pressure; because the pressure variable is fixed, the phase rule is expressed as P + F = C + 1.}}</ref>
:<math>F = C - P + 1</math>
This is sometimes incorrectly called the "condensed phase rule", but it is not applicable to condensed systems subject to high pressures (for example, in geology), since the effects of these pressures are important.<ref>{{Cite web |title=Phase rule |url=https://serc.carleton.edu/research_education/equilibria/phaserule.html |access-date=2022-10-09 |publisher=[[Science Education and Research Centre]] (SERC) at [[Carleton College]]}}</ref>