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2 Open Physics

2 2011

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First-principles LCAO study of phonons in NiWO4

100%

Kuzmin A. , Kalinko A. , Evarestov R.

Open Physics

2011

tom 9

nr 2

502-509

The electronic, structural and phonon properties of antiferromagnetic wolframite-type NiWO4 have been studied using first-principles spin-polarized LCAO calculations based on the hybrid Hartree-Fock (HF)/density functional (DFT) scheme. The influence of different percentages of HF contribution, i.e. different correlation strength, on the structure and phonon frequencies has been investigated and compared with the available experimental data.

Electronic excitations in ZnWO4 and ZnxNi1−x WO4 (x = 0.1 − 0.9) using VUV synchrotron radiation

86%

Kalinko A. , Kotlov A. , Kuzmin A. , Pankratov V. , Popov A. , Shirmane L.

Open Physics

2011

tom 9

nr 2

432-437

The photoluminescence spectra and luminescence excitation spectra of pure microcrystalline and nano-sized ZnWO4 as well as the ZnxNi1−x WO4 solid solutions were studied using vacuum ultraviolet (VUV) synchrotron radiation. The samples were also characterized by x-ray powder diffraction. We found that: (i) the shape of the photoluminescence band at 2.5 eV, being due to radiative electron transitions within the [WO6]6− anions, becomes modulated by the optical absorption of Ni2+ ions in the ZnxNi1−x WO4 solid solutions; and (ii) no significant change in the excitation spectra of Zn0.9Ni0.1WO4 is observed compared to pure ZnWO4. At the same time, a shift of the excitonic bands to smaller energies and a set of peaks, attributed to the one-electron transitions from the top of the valence band to quasi-localized states, were observed in the excitation spectrum of nano-sized ZnWO4.