Holes cause sodium nitride to behave like a metal

The unusual metallic behaviour of sodium nitride (Na₃N) is caused by the empty spaces in its structure, researchers have discovered.

Sodium nitride was predicted to be an insulator as it has similar structural features to some other clathrates, for example sodium oxide chloride (Na₃OCl). But unlike this white non-conducting material, Na₃N is a blueish–black solid with electronic properties that resemble a metal.