T.O. Parashchuk

Department of Physics and Chemistry of Solid State

N.D. Freik

Physics and Chemistry Institute, SHEE “Vasyl Stefanik Precarpathian National University”, Ivano-Frankivsk, Ukraine

P.M. Fochuk

Department of Inorganic Chemistry, Yuriy Fedkovych Chernivtsi National University, Chernivtsi, Ukraine