Abstract
Molecular dynamics simulations have been performed for the NaMg1-x Ca x F3 materials where Ca ions were substituted for Mg in NaMgF3 in varying concentrations of randomly distributed defects representing constitutional crossover. Small clusters of Ca defects in NaMgF3 and clusters of Mg defects in NaCaF3 were also studied. First-principles calculations were used to calculate the potentials between ion pairs in these samples. The change of defect concentration results in a gradual shift from nonfer-roelectric behavior of NaMgF3 to ferroelectric behavior of NaCaF3. Doping in these materials leads to a ‘‘smeared out'’ transition ‘‘range'’ instead of a sharp transition temperature—the so-called diffusive transition.
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