Ice XII is a metastable, dense, crystallinephase of solidwater, a type of ice. Ice XII was first reported in 1996 by C. Lobban, J.L. Finney and W.F. Kuhs and, after initial caution, was properly identified in 1998.
It was first obtained by cooling liquid water to Шаблон:Convert at a pressure of Шаблон:Convert. Ice XII was discovered existing within the phase stability region of ice V. Later research showed that ice XII could be created outside that range. Pure ice XII can be created from ice Ih at Шаблон:Convert by rapid compression (0.81-1.00 GPa/min) or by warming high density amorphous ice at pressures between Шаблон:Convert.
Ordinary water ice is known as ice Ih, (in the Bridgman nomenclature). Different types of ice, from ice II to ice XVI, have been created in the laboratory at different temperatures and pressures.
Ice XIV
When hydrochloric-acid-doped ice XII is cooled down to about 110 K, it undergoes a phase transition into a partially hydrogen-ordered phase, namely ice XIV.[1] The transition entropy from ice XIV to ice XII is estimated to be 60% of Pauling entropy based on DSC measurements.[2] The formation of ice XIV from ice XII is more favoured at high pressure.[3]
