Discovery of a neutral-to-ionic phase transition in organic materials

A systematic study of mixed stacked organic charge-transfer compounds shows that these materials are either neutral or ionic and that they range from being near the neutral-ionic boundary to being far away. Under pressure, several neutral compounds near this boundary are found to undergo a reversible phase transition to an ionic ground state. This is the first observation of a neutral-to-ionic transition in any kind of material. © 1981 The American Physical Society.