The crystal structure of ice VII

Scientists through study and experimentation have worked out how various forms of matter undergo shifts from gas, liquid and solid states. In scientific nomenclature ice Ih “hexagonal ice,” is the name of ordinary ice water found here on earth. However there are different structures of ice, from ice II to ice XVI, in the universe that have been created in the laboratory at different temperatures and pressures.  Until now Ice VII, which is a cubic crystalline form of ice has never been captured in transition in the laboratory, though its properties are well known.  But now for the first time Stanford researchers have captured the freezing of water, molecule-by-molecule, thanks to the the world’s most powerful X-ray laser found at the Linac Coherent Light Source,  located at the SLAC National Accelerator Laboratory.

Prototype Details

The Stanford team beamed an intense laser at a small target containing a sample of liquid water. The laser instantly vaporized and yielded a rocket-like force that compressed the water to pressures exceeding 50,000 times that of Earth’s atmosphere at sea level.   The platform developed for this study – combining laser beams, high pressure and snapshot images, captured the progression of lightening quick molecular changes Ice VII made.  The images were captured old style cartoon flip book-style, as the phase change took just 6 billionths of a second, or nanoseconds. The Stanford scientists were surprised to uncover in studying the images that water molecules bonded into rod shapes, and not spheres as theory predicted.

Benefits of Study and Platform Design

Ice VII can be found naturally in otherworldly environments, and may comprise the ocean floor of Saturn’s largest moon Titan as well as extrasolar planet.  Most ice phases including earth’s ice (“ice one-H”), the hydrogen atom positions are not orderly.  Ice VII is the only non-ordered phase of ice that can be ordered by simple cooling.  ice VII forms ordered ice below -0.15 Celsius making it the largest stability field range of all of the molecular phases of ice.  The study, found online July 11 in Physical Review Letters, gives hope that the platform the Stanford team built, will enable scientists to now investigate the plethora of ways water freezes, depending on pressure and temperature.  Studying these ice types thought to be of extraterrestrial origin, will help scientists study how the solar system formed and model remote cosmic body environments.