Department of Applied Physics, China Agricultural University, Beijing 100080, China.
Science. 2013 Dec 20;342(6165):1502-5. doi: 10.1126/science.1244989.
Sodium chloride (NaCl), or rocksalt, is well characterized at ambient pressure. As a result of the large electronegativity difference between Na and Cl atoms, it has highly ionic chemical bonding (with 1:1 stoichiometry dictated by charge balance) and B1-type crystal structure. By combining theoretical predictions and diamond anvil cell experiments, we found that new materials with different stoichiometries emerge at high pressures. Compounds such as Na3Cl, Na2Cl, Na3Cl2, NaCl3, and NaCl7 are theoretically stable and have unusual bonding and electronic properties. To test this prediction, we synthesized cubic and orthorhombic NaCl3 and two-dimensional metallic tetragonal Na3Cl. These experiments establish that compounds violating chemical intuition can be thermodynamically stable even in simple systems at nonambient conditions.
氯化钠（NaCl），又称岩盐，在常压下性质稳定。由于钠（Na）和氯（Cl）原子之间的巨大电负性差异，它具有高度离子键合（由电荷平衡决定的 1:1 化学计量比）和 B1 型晶体结构。通过理论预测和金刚石压腔实验相结合，我们发现高压下会出现具有不同化学计量比的新材料。理论上，像 Na3Cl、Na2Cl、Na3Cl2、NaCl3 和 NaCl7 这样的化合物是稳定的，它们具有不寻常的键合和电子性质。为了验证这一预测，我们合成了立方和正交相的 NaCl3 和二维金属四方相的 Na3Cl。这些实验证明，即使在非环境条件下的简单体系中，违反化学直觉的化合物也可以在热力学上稳定存在。
