Exactly soluble model with tricritical points for ferrodistortive structural phase transitions

We present and study a lattice dynamical model whose static and dynamic properties can be described exactly for all dimensions d and which, in addition, exhibits tricritical points. In the vicinity of an ordinary critical point, the critical exponents are those of the spherical model. The tricritical exponents, however, are classical and there is no logarithmic correction for d = 3. The critical dynamics is also discussed. © 1976, Taylor & Francis Group, LLC. All rights reserved.