A recent study published in the journal Nature Physics by a team from the University of Chicago describes the formation of a new ice form known as “superionic ice.” The ice that tinkles in our Coke glasses, known as Ih, is one of at least 19 different phases of ice.
One intriguing theory is that ice can become superionic when heated to extremely high temperatures and pressures. This unusual state would have liquid-like hydrogen ions travelling within a solid oxygen lattice. Superionic ice was first proposed in 1988, and a variety of studies have attempted to examine this phase of ice using simulation and static compression techniques.
Researchers generated a more stable type of ice by squeezing a water droplet with a 0.2-carat diamond anvil and blasting it with a laser at temperatures hotter than the sun’s surface. Ice has been given the title Ice XVIII (“Ice 18”) since it was the eighteenth type discovered. The oxygen atoms in the droplet were locked in Ice XVIII, but the hydrogen atoms, which formed positively charged ions, were free to circulate throughout the ice, acting like a fluid. The free-flowing ions prevented all light from penetrating the ice, leaving it dark.
In 2021, the Chicago team published a study that used similar methods to discover a new superionic ice phase. First, they heated the sample by squeezing water droplets to pressures of 20 GPa in a diamond anvil and firing lasers through the diamonds. They then used an X-ray beam to pass through the sample and observe how the X-rays scattered off the sample to piece together the arrangement of the atoms inside the superionic ice.
Many icy planets in our solar system, including Neptune, Uranus, and Jupiter’s moons Europa, Io, and Ganymede, also have magnetic fields like positively charged hydrogen ions in superionic ice. Scientists are now looking into whether these planets’ magnetic fields are generated by superionic ice in their cores.
This is an important subject because a planet’s magnetic field, or magnetosphere, prevents hazardous cosmic rays and UV radiation from reaching the planet’s surface and eradicating all life. If superionic ice is abundant in the cores of planets outside our solar system, it increases the likelihood of life in distant worlds.
When liquid water is chilled below 32 ° F, 0 ° C, or 273.15 ° K at atmospheric pressure, the most prevalent ice on Earth, Ih, forms. Ih has a six-sided, crystallin\e structure, which is mirrored in the infinite number of six-sided snowflakes. The oxygen atoms in Ih form a hexagonal pattern with hydrogen atoms. The hydrogen atoms are referred to as “disordered.”
The most common phase of ice on earth, Icec, has its atoms arranged in a diamond structure. The temperatures between 130 K (-226 °F) and 220 K (-64 °F) are ideal for forming this ice phase. It is present in the earth’s upper atmosphere, where they play a vital role at lower temperatures.
Ice II is a rhombohedral crystalline structure, with six faces in the form of rhombi, and it is created by compressing Ih at temperatures of 190 K (-118 °F) and 210 K (-82 °F). Finally, ice III has a tetragonal crystalline structure consisting of three axes at right angles, two out of the three are equal, and it is formed by cooling Ih down to temperatures of 250 K (-370 °F) at a pressure of 300 MPa. (1 Megapascal (MPa) is equal to 145.04 pounds psi.)
For the creation of Ice IV, which has a rhombohedral structure, one requires a nucleating agent that affects the temperature at which crystallization happens. Ice IV is the lowest, high-pressure ice phase available at room temperatures and found in diamond inclusions. It needs a pressure of 810 Mpa for its creation. Ice V is made by lowering the temperature of water to 253 K (-4.27 °F) at 500 MPa, and it has a complex crystalline structure, including 4-membered, 5-membered, 6-membered, and 8-membered rings and a total of 28 molecules in the unit cell.
Ice VI forms to take up a tetragonal crystalline structure and is made at temperatures up to 355 K (179.33 ° F) and a pressure of 1.1 GPa. The oxygen atoms in Ice VII form up in a cubic structure. This ice is unique because it stays stable even at extreme pressures, over 30,000 atmospheres (3 gigapascals). Researchers from the University of Nevada found the VII version of ice naturally on earth inside a diamondback in 2018.
And when Ice-VII is cooled down below temperatures 278 K (40.73 °F) at around 2.1 GPa, the hydrogen atoms assume fixed positions.
In 1968, Ice IX was discovered in a tetragonal structure formed from ice-3 by cooling it to temperatures between 208 K (-85.27 °F) to 165 K (-163 °F) with pressures between 200 MPa and 400 MPa. However, proton-ordered and symmetric atoms are found in Ice X, and it forms at around 60 to 70 GPa. Ice X is also thought to be stable to extreme temperatures.
Ice XI, discovered in 1996, is the proton-ordered phase of common ice and features similar to water dipoles. It can be synthesized in lab conditions at temperatures of around 72 K (-330 °F), and it is ferroelectric, which means that its atoms can be spontaneously polarized.
Ice XII is a tetragonal crystal structure. At 77 K (196.2°C; 321.1°F), pure ice XII can be created. High-density amorphous ice is heated to this condition at pressures ranging from 810 to 1600 MPa.
The monoclinic crystalline structure of Ice XIII, discovered in 2006, has three uneven axes. Water is doped with HCL and cooled to below 130 K (-226 °F) at 500 MPa to produce it. Ice XIV has an orthorhombic structure and is formed at pressures of 1.2 GPa at temperatures below 118 K (-247 °F). It’s protons-ordered ice XII.
Ice XV is a proton-ordered Ice VI variation. Cooling water to roughly 130 K (-226 °F) from pressures ranging from 0.8 to 1.5 GPa forms it. Ice XVI is the lightest crystalline form of water ever observed. In contrast, Ice XVII, also known as square ice, is formed when water is compressed between multiple graphene layers at more than 10,000 atmospheres of pressure at room temperature. This form of ice was discovered in 2014.
Ice XIX is the latest ice type, found in 2021 by a team from the University of Innsbruck and validated by Japanese specialists. This newest ice stage is a hydrogen-ordered VI with a randomly distributed pattern of hydrogen atoms.
“In terms of density, ice VI, ice XV, and ice XIX are all very similar [because] they share the same network of oxygen atoms. They differ, however, in terms of hydrogen atom positions,” Thomas Loerting, the lead scientist, said.