Unexpected Stable Stoichiometries of Sodium Chlorides

Salt to Squeeze

Simple table salt, NaCl, is the only known stable phase of Na and Cl at ambient conditions. Previous attempts to understand its structure and chemical properties under pressure and at high temperatures revealed phase and bonding transitions, while keeping the balance of one Na to one Cl. Using crystal structure prediction algorithms, Zhang et al. (p. 1502 ; see the Perspective by Ibáñez Insa ) show that other compounds—including Na ₃ Cl, Na ₂ Cl, Na ₃ Cl ₂ , NaCl ₃ , and NaCl ₇ are as stable as NaCl across a range of pressures.