Wydarzenia
Seminarium-mgr Pavlo Shchepanskyi
Data dodania: 10-05-2018 | Autor: Anna Chwał
W dniu 28 maja 2018r., o godz. 12:15, w Audytorium – sala 1023 budynku AJD przy al.Armii Krajowej 13/15, odbędzie się Seminarium, w trakcie którego mgr Pavlo Shchepanskyi (Zakład Fizyki Teoretycznej) wygłosi wykład pt. "Study of the influence of structural elements substitution on the anisotropic optical and electronic properties of ABSO4-group sulfates with isotropic points."
Streszczenie wykładu
Dielectric crystals of ABSO4 family, where A and B are alkali metal cations (Li, Na, K, Rb, Cs,...) or NH4 group attract a permanent attention of researchers stipulated by their ferroelectric, ferroelastic, superionic, optical and other properties. Among different aspects, an interest to the optical properties is due to the fact that the ABSO4-group crystals often reveal inversion of sign of the optical birefringence, or simply 'isotropic point', which occurs as a result of accidental increase in the symmetry of optical indicatrix, when crystal undergoes transition from biaxial to uniaxial or from uniaxial to isotropic. The latter is interesting from the fundamental point due interesting phenomena occurring near the isotropic point or immediately at this point. The effects of energy transfer between the normal light waves in the vicinity of isotropicpoint even have stimulated elaboration of a canonical coupled-mode theory. Effects related to the phenomenon of isotropic points have also found numerous applications ranging from temperature or pressure measuring to constructing narrow-band optical filters and determining the exact content of a substance.
Presented work is based on the experimental investigations of refractive properties of selected ABSO4-group crystals supported by the theoretical calculations of the structural and optical properties. Dispersion of refractive indices and birefringence along with baric and temperature changes of birefringence of LiNaSO4 and K1.75[NH4]0.25SO4 will be discussed. Possibility of the existence of isotropic points in the crystals will be analyzed.
The electronic properties and optical spectra calculations for crystals using DFT approach are carried out. The theoretically obtained data is compared with the experimental results. The effect of cation Li- Na substitution and partial isomorphic K -NH4 substitution on the optical anisotropy, dispersion and electronic properties of ABSO4-group crystals will be discussed. Presented investigations can serve as a fundament for prediction the materials with isotropic points on the base of structural and band-structure features.
Titled materials can be used as temperature and pressure sensors.