Pressure induced metallization of Cu3N
  We employed accurate full potential density-functional theory and linearized augmented plane wave method to investigate the electronic properties and possible phase transitions of Cu3N under high pressure. The anti perovskite structure Cu3N is a semiconductor with a small indirect band gap at ambient pressure. The band gap becomes narrower with increasing pressure, and the semi-conducting anti ReO3 structure undergoes a semiconductor to semimetal transition at pressure around 8.0 GPa. At higher pressure, a subsequent semimetal to metal transition could take place above 15GPa with a structural transition from anti ReO3 to Cu3Au structure. 
Wen Yu, Linyan Li and Changqing Jin