Bored with NaCl? Try NaCl2! or NaCl3, 4, 7?. Reduce your sodium in an unexpected way. Instructions here. NaCl7 is stable at pressures in excess of 142 GPa but the definition of stable here is a broad one: anything more stable than any competitor at the given physical space. The crystal structure is cubic with 4 sodium atoms on the corners and a central chlorine icosahedron. At elevated pressures chlorine is no longer much larger than sodium making these sort of structures possible. The material was prepared in a diamond anvil cell from NaCl with additional chlorine and laser heating and then analysed with XRD and Raman.