Fast Crystallization Driven by Quasiatomic Electrons at Ultralow Temperatures

In electride liquids, electrons detach from atomic orbitals and freely occupy the interstitial regions, forming quasiatomic electrons. Here, using dense electride potassium liquid as an example, we uncover a fast crystallization behavior at ultralow temperatures. By combining machine-learned molecular dynamic simulations and ab initio calculations, we demonstrate that this rapid crystallization is attributed to quasiatomic electron flexibility, i.e., self-accommodation of atom size with the help of the change of quasiatomic electrons, particularly the population of involved quasiatomic electrons that is enhanced at low temperatures. This effect not only accelerates atomic mobility but also softens the stiffness of the solid-liquid interface, triggering supercollective atomic motion and enabling rapid crystallization. Our findings challenge conventional views of crystallization kinetics and reveal a previously unrecognized mechanism where electronic contributions play a dominant role in dictating metallic solidification.