2. Equilibria in solid phases

The ice diagram, outlined by Bridgman , is extremely rich since, in 2005, in addition to the three amorphous forms of ice (known as low, high, and very high density), fifteen crystalline varieties of ice were listed, numbered from I to XIV, with ice I itself comprising two varieties: stable Ih (hexagonal) ice and metastable Ic (cubic) ice. All snow or ice found naturally on Earth is Ih ice. The varieties recognized as metastable are Ic, IV, IX, and XII ice. Ic ice can be obtained by condensing water vapor below –80°C; Ic and Ic ice result from slow heating (< 15 K/min for Ic ice) or rapid heating (> 15 K/min...