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RESEARCH PRODUCT
Negative pressures in CaWO4 nanocrystals
Alfonso MunozJavier López-solanoDaniel ErrandoneaFrancisco Javier ManjonPlácida Rodríguez-hernándezsubject
Phase transitionMaterials scienceCalcium compoundsAb initioUNESCO::FÍSICAGeneral Physics and AstronomyNanoparticleNanostructured materialsCrystal symmetryCrystallographyTetragonal crystal systemNanocrystalAb initio quantum chemistry methodsChemical physicsTotal energy:FÍSICA [UNESCO]Phase (matter)Ab initio calculations ; Calcium compounds ; Crystal growth from solution ; Crystal symmetry ; Nanostructured materials ; Solid-state phase transformations ; Total energySolid-state phase transformationsAb initio calculationsCrystal growth from solutionMonoclinic crystal systemdescription
Tetragonal scheelite-type CaWO4 nanocrystals recently prepared by a hydrothermal method show an enhancement of its structural symmetry with the decrease in nanocrystal size. The analysis of the volume dependence of the structural parameters in CaWO4 nanocrystals with the help of ab initio total-energy calculations shows that the enhancement of the symmetry in the scheelite-type nanocrystals is a consequence of the negative pressure exerted on the nanocrystals; i.e., the nanocrystals are under tension. Besides, the behavior of the structural parameters in CaWO4 nanocrystals for sizes below 10 nm suggests an onset of a scheelite-to-zircon phase transformation in good agreement with the predictions from our ab initio calculations. CaWO4 nanocrystals exhibit a reconstructive-type mechanism for the scheelite-to-zircon phase transition that seems to follow the tetragonal path that links both structures. This result is in contrast with the mechanism recently proposed for this transition in bulk ZrSiO4 where the transition goes through an intermediate monoclinic phase. Daniel.Errandonea@uv.es
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2009-05-01 |