The dilute spin-1 ising model with crystal-field interactions

2D spin-1 Ising models with nearest-neighbour and crystal-field interactions exhibit tricritical behaviour. A new method that applies to a wide class of random systems is used to study the influence of site and bond dilution on this behaviour. We have calculated temperature-crystal-field-concentration phase diagrams and determined, in particular, the influence of dilution on the zero-temperature critical field and on the tricritical temperature. Our results are in agreement with those obtained recently for bond dilution by a real-space renormalisation-group technique. Our method appears more tractable. © 1985 The Institute of Physics.