Researchers from Ohio State University have created an extremely cubic ice crystal, and yes that’s different from an ice cube you make in the freezer. Water molecules don’t like being in a cubic structure, preferring to create hexagonal patterns (like in snowflakes). However, they can be forced into a cubic arrangement under the right conditions.
The team supercooled water droplets to -48°C (-55°F) after shooting them from a supersonic nozzle. The droplets froze in about one-millionth of a second and were organized in crystals where almost 80 percent of the molecules were in a cubic structure, while the rest stayed in a hexagonal one. This success is reported in the Journal of Physical Chemistry Letters.
“While 80 percent might not sound ‘near perfect,’ most researchers no longer believe that 100 percent pure cubic ice is attainable in the lab or in nature,” project leader Professor Barbara Wyslouzil said in a statement. “So the question is, how cubic can we make it with current technology? Previous experiments and computer simulations observed ice that is about 75 percent cubic, but we’ve exceeded that.”
Cubic ice is mostly created in the lab, but researchers think that it could also form high in the atmosphere, where the right conditions exist for water droplets to be supercooled quickly. When it comes to this, speed is just as important as temperature.
“When water freezes slowly, we can think of ice as being built from water molecules the way you build a brick wall, one brick on top of the other,” added Claudiu Stan, a research associate at the Stanford PULSE Institute at SLAC and partner in the project. “But freezing in high-altitude clouds happens too fast for that to be the case – instead, freezing might be thought as starting from a disordered pile of bricks that hastily rearranges itself to form a brick wall, possibly containing defects or having an unusual arrangement.”
The scientists used the Linear Coherent Light Source, the powerful X-ray laser that is part of the SLAC National Accelerator Laboratory. Using the laser, researchers were able to get a glimpse at how these crystals are structured, although it is still unclear how they form.
“This kind of crystal-making process is so fast and complex that we need sophisticated equipment just to begin to see what is happening,” Stan concluded. “Our research is motivated by the idea that in the future we can develop experiments that will let us see crystals as they form.”
We will just have to wait and see.