Density Functional Perturbation Theory Analysis of Negative Thermal Expansion Materials: A Combined Computational and Experimental Study of α-ZrW2O8

Cubic zirconium tungstate (α-ZrW2O8), a notorious negative thermal expansion (NTE) material, has been investigated within the framework of density functional perturbation theory (DFPT), combined with experimental characterization to assess and validate computational results. Spectroscopic, mechanical and thermodynamic properties have been derived from DFPT calculations. A systematic comparison of DFPT-simulated infrared, Raman, and phonon density-of-state spectra with Fourier transform far-/mid-infrared and Raman data collected in this study, as well as with available inelastic neutron scattering measurements, shows the supe-rior accuracy of the PBEsol exchange-correlation functional over standard PBE calculations. The thermal evolution of the Grüneisen parameter computed within the quasi-harmonic approximation exhibits negative values below the Debye temperature, consistent with the observed NTE characteristics of α-ZrW2O8. The standard molar heat capacity is predicted to be C$0\atop{P}$=193.8 and 192.2 J.mol-1.K-1 with PBE and PBEsol, respectively, ca. 7% lower than calorimetric data. In conclusion, these results demonstrate the accuracy of the DFPT/PBEsol approach for studying the spectroscopic, mechanical and thermodynamic properties of materials with anomalous thermal expansion.