Cooperative Jahn-Teller transitions with tripling of the period: CaCuCI3
Khomskii D.I.
It is shown that the cooperative Jahn-Teller effect can be accompanied by a structural transition with tripling of the period, similar to the transition observed in CsCuCl3. The absence of softening of the phonons with q =2тг/3с at T> Tc is explained. It is shown that uniaxial pressure can alter the period of the low-temperature phase.