Giant Lasers Flash-Freeze and Crystallize Water to Reveal Superionic Structure

Scientists from Lawrence Livermore National Laboratory (LLNL) used giant lasers to flash-freeze water into its exotic superionic phase and record X-ray diffraction patterns to identify its atomic structure for the very first time — all in just a few billionths of a second.

Superionic ice is a mix of a solid lattice of oxygen and liquid-like hydrogen. This should exist at the heart of Uranus and Neptune.

Using laser-driven shockwaves and in-situ X-ray diffraction, they observe the nucleation of a crystalline lattice of oxygen in a few billionths of a second, revealing for the first time the microscopic structure of superionic ice.

They used six giant laser beams to generate a sequence of shockwaves of progressively increasing intensity to compress a thin layer of initially liquid water to extreme pressures (100-400 gigapascals (GPa), or 1-4 million times Earth’s atmospheric pressure) and temperatures (3,000-5,000 degrees Fahrenheit).

Nature – Nanosecond X-ray diffraction of shock-compressed superionic water ice

They used laser-driven shockwaves to simultaneously compress and heat liquid water samples to 100–400 gigapascals and 2,000–3,000 kelvin. In situ X-ray diffraction measurements show that under these conditions, water solidifies within a few nanoseconds into nanometre-sized ice grains that exhibit unambiguous evidence for the crystalline oxygen lattice of superionic water ice. The X-ray diffraction data also allow them to document the compressibility of ice at these extreme conditions and a temperature- and pressure-induced phase transformation from a body-centered-cubic ice phase (probably ice X) to a novel face-centred-cubic, superionic ice phase, which they named ice XVIII.