Abstract
Estimates of the tricritical point (Tt, (J4/J2)x) within an effective-field treatment are obtained for the Ising model with pair and quartet interactions. The lattices considered are the FCC, BCC and SC lattices with conventional quartets, and the SC lattice with square quartets. A correlated effective-field method is used to obtain a criticality relation between an effective field lambda and the coupling ratio J4/J2 for which the criticality equation has no solution for lambda . Tt is found from the phase boundary equation. If is found that lambda =0 at the tricritical point, for the FCC lattice.

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