Fe b 19 99 Thermodynamics of the incommensurate state in Rb 2 WO
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چکیده
We consider the evolution of the phase transition from the parent hexagonal phase P63/mmc to the orthorhombic phase Pmcn that occurs in several compounds of A′A′′BX4 family as a function of the hcp lattice parameter c/a. For compounds of K2SO4 type with c/a larger than the threshold value 1.26 the direct first-order transition Pmcn−P63/mmc is characterized by the large entropy jump ∼ R ln 2. For compounds Rb2WO4, K2MoO4, K2WO4 with c/a < 1.26 this transition occurs via an intermediate incommensurate (Inc) phase. DSC measurements were performed in Rb2WO4 to characterize the thermodynamics of the Pmcn − Inc − P63/mmc transitions. It was
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تاریخ انتشار 2008