Us Earthlings are quite lucky to be living at around standard temperature and pressure. Life has evolved to comfortably handle the shapes most molecules arrange themselves in at one atmosphere of pressure at whichever temperature nature is capable of throwing at us. But on other planets, at other temperatures and pressures, lots of things we take for granted would probably just kill us. Even the usual killers might be worse.
Take your friendly, colourless, odourless murder machine, carbon monoxide. It’s a gas here on Earth. But an international team of physicists ran a simulation of the possible ways carbon monoxide molecules could arrange themselves, and found that when formed at the right pressure, it’s a polymer that could be a powerful explosive. They published their research this month in Physical Review B.
Carbon monoxide is an especially prevalent molecule in interstellar space, pointed out Dennis Klug, Principal Research Scientist at the National Research Council of Canada in Ottawa. “If that’s the case, it’s going to occur in many different environments and have lots of time to evolve, including into this structure we predict,” a structure that seems to be stable even at low energies, he told Gizmodo.
Carbon monoxide’s ability to form polymers—molecules made from a base piece that repeats, including plastics—isn’t a new insight, but the researchers applied a fairly new method called “Ab initio random structure searching” to scan through the ways the molecules might arrange themselves at different pressures, using the laws of chemistry and quantum mechanics. The method approaches near god-mode chemistry predicting abilities, where researchers plug in some molecules and other parameters and receive what the structure of the molecule would look like, which could lead to information on its properties.
Contrary to what you might expect, the team’s search found that the most stable carbon monoxide structure at ambient pressure and temperature would be a polymer, a repeating molecule with a backbone of carbon and oxygen rings called Pna21. But this stuff couldn’t form spontaneously—it needs to be made at high pressures, maybe around ten thousand times higher than sea level pressure. And unlike other carbon monoxide polymers discovered previously, Pna21 would be absolutely explosive, five to ten times more so than the same amount of TNT, thanks to the huge amount of energy it stores.
We don’t see carbon monoxide form this way on Earth, but the polymer could exist elsewhere in the galaxy, maybe inside planets or gas clouds.
It’s important to note that these computer algorithm searches for new chemical structures are carried out at a temperature of absolute zero, something unachievable in our natural universe. Adding temperature and entropy, the relative disorder of the system, into the mix would be important, Nicholas Harrison, physicist at Imperial College, London, told Gizmodo. Additionally, he said, at room temperatures these polymers might rapidly oxidise into carbon dioxide. Harrison had no idea how this thing would behave at an ambient pressure at room temperature in the presence of other molecules.
But Harrison was excited about the computational algorithm, given the importance of a crystal’s structure to its properties.
As for applications, who knows? Scientists have only theorised that this Pna21 polymer exists, they haven’t made it. Maybe we can suck carbon dioxide from the atmosphere and store or transport energy in these carbon monoxide crystals. There are probably way better molecules for doing that job, but it’s nice to think about what sorts of problems strange chemistry might help us solve.
Anyway, literally everything can kill you if you try hard enough and believe in yourself. Chaos reigns. [Phys Rev B]