Combined computational and experimental study of zirconium tungstate

摘要

We have investigated cubic zirconium tungstate(ZrW_2O_8) using density functional perturbation theory(DFPT), along with experimental characterization toassess and validate computational results. Cubiczirconium tungstate is among the few known materialsexhibiting isotropic negative thermal expansion (NTE)over a broad temperature range, including roomtemperature where it occurs metastably. Isotropic NTEmaterials are important for technological applicationsrequiring thermal-expansion compensators in compositesdesigned to have overall zero or adjustable thermalexpansion. While cubic zirconium tungstate has attractedconsiderable attention experimentally, a very fewcomputational studies have been dedicated to this wellknownNTE material. Therefore, spectroscopic,mechanical and thermodynamic properties have beenderived from DFPT calculations. A systematiccomparison of the calculated infrared, Raman, andphonon density-of-state spectra has been made withFourier transform far-/mid-infrared and Raman datacollected in this study, as well as with available inelasticneutron scattering measurements. The thermal evolutionof the lattice parameter computed within the quasiharmonicapproximation exhibits negative values belowthe Debye temperature, consistent with the observednegative thermal expansion characteristics of cubiczirconium tungstate, α-ZrW_2O_8. These results show thatthis DFPT approach can be used for studying thespectroscopic, mechanical and thermodynamic propertiesof prospective NTE ceramic waste forms forencapsulation of radionuclides produced during thenuclear fuel cycle.