Salt in a glass of water is a crowd of charged particles. When there's plenty of water, each particle floats on its own, wrapped in a thick fur coat of water molecules. But as you keep adding salt, the water runs out for everyone, and the particles start seeking each other out. First, they stick together in pairs, then in larger clumps. At some point, the clumps become so heavy that they sink to the bottom — that's the solubility limit.
The authors of the new study built a computational pipeline that tracks a single lithium particle in a lithium chloride solution. To avoid waiting for rare encounters, they artificially nudged the particle and then recalculated its real chances of ending up in a pair or a clump. They added a correction for the fact that a small computer box has less free water than a real glass — and got a picture that matches experiment.
The method is called SCOPE. It isn't tied to lithium or chlorine: you can use it to dissect any concentrated liquid where rare encounters and collective behavior matter, such as battery brines or water-treatment fluids.
Lithium chloride is so hygroscopic that it dissolves into a puddle on the air, soaking up moisture from the room.