Unusual electronic and mechanical properties of sodium chlorides at high pressures

• We performed systematic investigation on the electronic and mechanical properties of NamCln.
• The extended Cl (or Na) sublattice at Cl-rich (or Na-rich) conditions contributes to the metallization at high pressures.
• The NamCln crystals exhibit good ductility in contrast to the brittle NaCl crystal.
• The P4/mmm-Na3Cl possesses the best ductility and the semiconducting Pnma-NaCl3 has the largest hardness.

Using first-principles calculations, we performed systematic investigation on the electronic and mechanical properties of sodium chlorides with different stoichiometries at high pressures. It was found that most of the phases are metallic except the Pnma-NaCl3 with a gap of 2.155 eV. The extended Cl (or Na) sublattice at Cl-rich (or Na-rich) conditions contributes to the metallization. Accompanied by metallization, the NamCln crystals exhibit good ductility in contrast to the brittle NaCl crystal, due to the changes of binding features induced by high pressure. These results are expected to be useful for understanding the exotic properties of NaCl at high pressures.