Ice VI is a form of
ice that exists at
high pressure at the order of about 1
GPa (= 10 000
bar) and temperatures ranging from 130 up to 355 Kelvin (−143 °C up to 82 °C); see also the phase diagram of water. Its discovery and the discovery of other high-pressure forms of water were published by
P.W. Bridgman in January 1912.[1]
It is part of one of the inner layers of
Titan.[2]
Properties
Ice VI has a
density of 1.31 g/cm3 and a
tetragonal crystal system with the
space group P42/nmc; its
unit cell contains 10 water molecules and has the dimensions a=6.27
Å and c=5.79 Å.[3]
The
triple point of ice VI with
ice VII and liquid water is at about 82 °C and 2.22 GPa and its triple point with
ice V and liquid water is at 0.16 °C and 0.6324 GPa = 6324 bar.[4]
Ice VI undergoes phase transitions into ices
XV[5] and XIX [6] upon cooling depending on pressure as
hydrochloric acid is doped.