Editing Triple point (section)

=== High-pressure phases ===
At high pressures, water has a complex [[phase diagram]] with 15 known [[Ice#Phases|phases of ice]] and several triple points, including 10 whose coordinates are shown in the diagram. For example, the triple point at 251&nbsp;K (−22&nbsp;°C) and 210&nbsp;MPa (2070&nbsp;atm) corresponds to the conditions for the coexistence of [[ice Ih]] (ordinary ice), [[ice III]] and liquid water, all at equilibrium. There are also triple points for the coexistence of three solid phases, for example [[ice II]], ice V and ice VI at 218&nbsp;K (−55&nbsp;°C) and 620&nbsp;MPa (6120&nbsp;atm).

For those high-pressure forms of ice which can exist in equilibrium with liquid, the diagram shows that melting points increase with pressure. At temperatures above 273&nbsp;K (0&nbsp;°C), increasing the pressure on water vapor results first in liquid water and then a high-pressure form of ice. In the range {{val|251|-|273|u=K}}, ice&nbsp;I is formed first, followed by liquid water and then ice&nbsp;III or ice&nbsp;V, followed by other still denser high-pressure forms.

[[File:Phase_diagram_of_water.svg|class=skin-invert-image|thumb|upright=3.3|center|Phase diagram of water including high-pressure forms ice&nbsp;II, ice&nbsp;III, etc. The pressure axis is logarithmic. For detailed descriptions of these phases, see [[Ice#Phases|Ice]].]]

{| class="wikitable" 
|+ The various triple points of water
! Phases in stable equilibrium
! Pressure
! Temperature
|-
| liquid water, [[ice Ih|ice I<sub>h</sub>]], and water vapor
| 611.657 Pa<ref>{{cite journal |doi=10.1256/qj.04.94 | volume=131 | issue=608 | title=Review of the vapour pressures of ice and supercooled water for atmospheric applications | year=2005 | journal=Quarterly Journal of the Royal Meteorological Society | pages=1539–1565 | last1 = Murphy | first1 = D. M.| bibcode=2005QJRMS.131.1539M | s2cid=122365938 | url=https://zenodo.org/record/1236243 | doi-access=free }}</ref>
| 273.16 K (0.01&nbsp;°C)
|-
| liquid water, ice I<sub>h</sub>, and [[ice III]]
| 209.9 MPa
| 251 K (−22&nbsp;°C)
|-
| liquid water, ice III, and [[ice V]]
| 350.1 MPa
| −17.0&nbsp;°C
|-
| liquid water, ice V, and [[ice VI]]
| 632.4 MPa
| 0.16&nbsp;°C
|-
| ice I<sub>h</sub>, [[Ice II]], and ice III
| 213 MPa
| −35&nbsp;°C
|-
| ice II, ice III, and ice V
| 344 MPa
| −24&nbsp;°C
|-
| ice II, ice V, and ice VI
| 626 MPa
| −70&nbsp;°C
|}
{{clear}}