Keywords :
First-principle density-functional theories; First-principle study; Hybrid functional; Hybrid functionals; Lattice dynamical properties; Metastable phase; Structure and energetics; Theoretical study; Zone-center phonons; Electronic, Optical and Magnetic Materials; Condensed Matter Physics; Physics - Materials Science
Abstract :
[en] Using first-principles density functional theory, we investigate the dynamical properties of the room-temperature P21/n and ground-state P21/c phases of WO3. As a preliminary step, we assess the validity of various standard and hybrid functionals, concluding that the best description is achieved with the B1-WC hybrid functional while a reliable description can also be provided using the standard LDA functional. We also carefully rediscuss the structure and energetics of all experimentally observed and a few hypothetical metastable phases in order to provide deeper insight into the unusual sequence of phase transition of WO3 with temperature. Then, we provide a comprehensive theoretical study of the lattice dynamical properties of the P21/n and P21/c phases, reporting zone-center phonons, infrared and Raman spectra, as well as the full phonon dispersion curves, which attest to the dynamical stability of both phases. We carefully discuss the spectra, explaining the physical origin of their main features and evolution from one phase to another. We reveal a systematic connection between the dynamical and structural properties of WO3, highlighting that the number of peaks in the high-frequency range of the Raman spectrum appears as a fingerprint of the number of antipolar distortions that are present in the structure and a practical way to discriminate between the different phases.
Funding text :
This work has been funded by the Communauté Française de Belgique (ARC AIMED G.A. 15/19-09) and a Methusalem project of the University of Antwerp. E.B. thanks the FRS-FNRS for support. The authors acknowledge the CECI supercomputer facilities funded by the FRS-FNRS (Grant No. 2.5020.1), the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles funded by the Walloon Region (Grant No. 1117545), and the computing facilities of the Flemish Supercomputer Center. We acknowledge that the results of this research have been achieved using the DECI resource BEM based in Poland at Wrocław with support from the PRACE OFFSPRING project.
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