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Information × Registration Number 0311U003998, 0109U004329 , R & D reports Title Refractive parameters of monocrystals and nanosized ferroics under the external fields influence popup.stage_title Рефрактивні параметри монокристалічних і нанорозмірних фероїків під впливом зовнішніх полів Head Stadnyk Vasyl, Kapustianyk Volodymyr, Registration Date 13-12-2011 Organization Ivan Franko National University of Lviv popup.description2 It was studied the spectral and temperature dependences of the refractive indices, birefringence, the piezooptic constants and infrared reflection spectra; calculated of the parameters of effective ultraviolet and infrared oscillators, electron polarizability, refraction, as well as the optical constants of both mechanically free and uniaxially stressed dielectric crystals K2ZnCl4 at temperature range 77-700 K. The calculations on the basis of the first time ab-initio investigations of the band electronic structure, density of states and optical functions of K2ZnCl4 crystal. The valence-conduction band gap Eg of the crystal is found to be of the direct type in the Г-point of Brillouin zone and to be formed by the electronic states of ZnCl4 complexes only. One of the features of band structure of K2ZnCl4 is a presence of separated two groups of conduction bands, which are originated from different electrons: first group, at the bottom of conduction bands, is originated mainly from ZnCl4 ions and second group of higher energies derives mainly from d-electrons of potassium. It is revealed that the ni values mainly increase under the action of uniaxial stresses, while the corresponding increments are the largest in the ultraviolet spectral range. These facts are caused by increment of the electron polarizability, the bonds refraction and the displacement of the absorption spectra to the longwave region. The uniaxial mechanical pressure along the principal crystallophysical axes is shown to give rise to shifting the PT points towards higher or lower temperatures, depending on the influence of uniaxial pressures upon the crystalline structure. Product Description popup.authors Бовгира Олег Вікторович Капустяник Володимир Богданович Стадник Василь Йосифович popup.nrat_date 2020-04-02 Close