Estudo da transição de fase de 1ª ordem no KH2PO4

Abstract

Recent experimental data show that the KDP phase transition is of the first order. The well Known model hamiltonian for KDP, na Ising interaction on a transverse field for pseudo-spins operators, produces a second order phase transition. In order to reproduce the correct order of transition we have add to the model hamiltonian three-and four-particule terms, which are directly connected to the pieroelectric interaction which exists in this system. We can also show that this modified pseudo-spin model hamiltonian gives essentially the same results obtained by phenomenological treatment.