2012/11/15 by Weiwei Zhang, Zhang, Weiwei, Artem R. Oganov +13 · 1 citation
Chemistry · Earth and Planetary Sciences · Materials Science · #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #High-pressure geophysics and materials #Inorganic Chemistry and Materials #Materials Science (cond-mat.mtrl-sci) #Other Condensed Matter (cond-mat.other) #Thermal and Kinetic Analysis
paper · pdf · doi:10.48550/arxiv.1211.3644
openalex publication_date 2012/11/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
At ambient pressure, sodium, chlorine, and their only known compound NaCl, have well-understood crystal structures and chemical bonding. Sodium is a nearly-free-electron metal with the bcc structure. Chlorine is a molecular crystal, consisting of Cl2 molecules. Sodium chloride, due to the large electronegativity difference between Na and Cl atoms, has highly ionic chemical bonding, with stoichiometry 1:1 dictated by charge balance, and rocksalt (B1-type) crystal structure in accordance with Pauling's rules. Up to now, Na-Cl was thought to be an ultimately simple textbook system. Here, we show that under pressure the stability of compounds in the Na-Cl system changes and new materials with different stoichiometries emerge at pressure as low as 25 GPa. In addition to NaCl, our theoretical calculations predict the stability of Na3Cl, Na2Cl, Na3Cl2, NaCl3 and NaCl7 compounds with unusual bonding and electronic properties. The bandgap is closed for the majority of these materials. Guided by these predictions, we have synthesized cubic NaCl3 at 55-60 GPa in the laser-heated diamond anvil cell at temperatures above 2000 K.