page_title: Ice Ih
hierarchical_section_title: Ice Ih
caption_attribution_description: English: Phase space of Ice Ih in the phase diagram of ice.
context_page_description: Ice Iₕ is the hexagonal crystal form of ordinary ice, or frozen water. Virtually all ice in the biosphere is ice Iₕ, with the exception only of a small amount of ice Ic that is occasionally present in the upper atmosphere. Ice Iₕ exhibits many peculiar properties that are relevant to the existence of life and regulation of global climate.
  The crystal structure is characterized by the oxygen atoms forming hexagonal symmetry with near tetrahedral bonding angles. Ice Iₕ is stable down to −268 °C, as evidenced by x-ray diffraction and extremely high resolution thermal expansion measurements. Ice Iₕ is also stable under applied pressures of up to about 210 megapascals where it transitions into ice III or ice II.
context_section_description: Ice Iₕ (hexagonal ice crystal)(pronounced: ice one h, also known as ice-phase-one) is the hexagonal crystal form of ordinary ice, or frozen water. Virtually all ice in the biosphere is ice Iₕ, with the exception only of a small amount of ice Ic that is occasionally present in the upper atmosphere. Ice Iₕ exhibits many peculiar properties that are relevant to the existence of life and regulation of global climate. For a description of these properties, see Ice, which deals primarily with ice Iₕ.
  The crystal structure is characterized by the oxygen atoms forming hexagonal symmetry with near tetrahedral bonding angles. Ice Iₕ is stable down to −268 °C (5 K; −450 °F), as evidenced by x-ray diffraction and extremely high resolution thermal expansion measurements. Ice Iₕ is also stable under applied pressures of up to about 210 megapascals (2,100 atm) where it transitions into ice III or ice II.
caption: Phase space of ice Ih with respect to other ice phases.
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