Phase transitions in wolframite-type<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>CdWO</mml:mtext></mml:mrow><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>at high pressure studied by Raman spectroscopy and density-functional theory

Lacomba-Perales, R.; Errandonea, Daniel; Martínez‐García, D.; Rodríguez‐Hernández, P.; Radescu, S.; Mújica, A.; Múñoz, A.; Chervin, J. C.; Polian, A.

doi:10.1103/physrevb.79.094105

Cited by 69 publications

(93 citation statements)

References 39 publications

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“…Note that the plane-wave PBE calculations [7] tend to underestimate the highest frequency stretching W-O mode by approximately 50 cm −1 . In fact, such underestimation appears typical for the plane-wave PBE scheme and was previously observed in other related tungstates: by ∼45 cm −1 in ZnWO 4 [47] and by ∼32 cm −1 in CdWO 4 [48]. We believe that the LCAO approach based on the local description of the electron wave functions can more accurately predict the local vibration frequencies when it is used in conjunction with the hybrid functionals and a properly optimised basis set.…”

Section: Phonon Structurementioning

confidence: 92%

Ab initio LCAO study of the atomic, electronic and magnetic structures and the lattice dynamics of triclinic CuWO4

2013

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The electronic, structural and phonon properties of antiferromagnetic triclinic CuWO 4 have been studied using the first-principle spin-polarised linear combination of atomic orbital (LCAO) calculations based on the hybrid exchange-correlation density functional (DFT)/Hartree-Fock (HF) scheme.In addition, the local atomic structure around both Cu and W atoms has been probed using the extended X-ray absorption fine structure (EXAFS) spectroscopy. We show that by using the hybrid DFT-HF functional, one can accurately and simultaneously describe the atomic structure (the unit cell parameters and the atomic fractional coordinates), the band gap and the phonon frequencies. In agreement with our EXAFS results, the LCAO calculations reproduce a strong distortion of both the CuO 6 and the WO 6 octahedra, which occur due to the first-order and second-order Jahn-Teller * Corresponding author Email address: a.kuzmin@cfi.lu.lv (A. Kuzmin) URL: http://www.cfi.lv/ (A. Kuzmin) January 2, 2013 effects, respectively. We found that the HF admixture of 13-16%, which is implemented in the PBE0-13% and WCGGA-PBE-16% functionals, produces the best result for CuWO 4 . The calculated properties agree well with the available experimental data provided by diffraction, optical, X-ray photoelectron and Raman spectroscopies. Preprint submitted to Elsevier

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Section: Phonon Structurementioning

confidence: 92%

Ab initio LCAO study of the atomic, electronic and magnetic structures and the lattice dynamics of triclinic CuWO4

2013

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“…Remarkably, the frequency of the highest A u mode amounts to 859 cm −1 , which is unusually high for a transition-metal oxide in which oxygen is the only light element. However, comparable values have been reported for other tungstates AWO 4 with divalent A = Cd, Ni, or Mg. [63][64][65][66][67] This mode can be assigned to a symmetric W-O(2) bond stretching phonon. The high frequency reflects the strong bonding between the nominally hexavalent W ions and the O(2) ions, as the shortest W-O(2) bond in MnWO 4 amounts to only 1.79Å (see Fig.…”

Section: A Au Phonon Modesmentioning

confidence: 99%

Infrared-active phonon modes in monoclinic multiferroicMnWO4

et al. 2014

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We report on polarized infrared reflectivity measurements of multiferroic, monoclinic MnWO4 between 10 K and 295 K. All five non-vanishing components of the dielectric tensor have been determined in the frequency range of the phonons. All infrared-active phonon modes (7 Au modes and 8 Bu modes) are unambiguously identified. In particular the strongest Bu modes have been overlooked in previous studies, in which the monoclinic symmetry was neglected in the analysis. The combined analysis of reflectance data measured in different experimental geometries (Rac and Rp) is particularly helpful for a proper identification of the Bu modes. Using a generalized Drude-Lorentz model, we determine the temperature dependence of the phonon parameters, including the orientation of the Bu modes within the ac plane. The phonon parameters and their temperature dependence were discussed controversially in previous studies, which did not include a full polarization analysis. Our data do not confirm any of the anomalies reported above 20 K. However, in the paramagnetic phase we find a drastic reduction of the spectral weights of the weakest Au mode and of the weakest Bu mode with increasing temperature. Below 20 K, the parameters of the Au phonon modes for E b show only subtle changes, which demonstrate a finite but weak coupling between lattice dynamics and magnetism in MnWO4. A quantitative comparison of our infrared data with the quasi-static dielectric constant ε b yields a rough estimate for the oscillator strength ∆εem 0.02 of a possible electromagnon for E b. Furthermore, we report on a Kramers-Kronig-consistent model which is able to describe non-Lorentzian line shapes in compounds with monoclinic symmetry.

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“…However, there are small discrepancies that suggest that, despite being all the HP phase structurally related to wolframite, there are some differences in the their HP phases. These can be clearly seen when comparing the Raman spectra published for the HP phases of CdWO4 [18] and MnWO4 [20]. In CdWO4 the phase transition to the post-wolframite structure leads to a doubling of the unit-cell (hence, the formula unit increases from 2 to 4) [14], with the consequent increase in the number of Raman modes.…”

Section: Raman Spectroscopymentioning

confidence: 79%

“…They have been assigned to 19 Ag + 17 Bg modes. Out of them, only twenty-six modes have been observed [14,18]. The frequency of these modes and the pressure coefficients are summarized in Table IV.…”

Section: Raman Spectroscopymentioning

confidence: 99%