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Information × Registration Number 0215U003036, 0114U002688 , R & D reports Title Hydrogen phase transitions in thin films and bulk specimens of metals popup.stage_title Head Kosogor A, Registration Date 15-01-2015 Organization Institute of magnetism of NASU popup.description2 In the framework of the project the theoretical solubility isotherms of hydrogen adsorption in metal (in the variable plane hydrogen pressure-hydrogen concentration) for the thin films and bulk specimens of vanadium. To this end the Landau theory was adapted for the description of interplay between crystal lattice symmetry and spatial hydrogen configuration. Comparing theoretical and experimental solubility isotherms shows that Landau theory is an adequate tool for the modeling of basic characteristics of experimental solubility isotherms. Solubility isotherms shows: the elevation of horizontal plateau-like segment (which correspond to the hydrogen phase transition) of the isotherm upon heating of the specimen; the narrowing of the plateau-like segment upon heating of the specimen and a disappearance of the hydrogen phase transition at temperatures higher than the critical temperature. However, in contrast to the bulk materials, the axial stress is omnipresent in thin films and superlattices, which distorts the unit cells of the host lattice. The axial stress reduces the symmetry of the host lattice and therefore provokes the hydrogen phase transition. According to this, the axial stress noticeably changes the computational results and provides a quantitative agreement of experimental and theoretical solubility isotherms. The calculations show that 1) the critical temperature decreases exponentially with increasing stress; 2) the axial stress narrows the interval of the applicability of Sieverts' law; and 3) the axial stress increases the empirically determined value K, which is involved in Sieverts' law. Product Description popup.authors Косогор А.В. popup.nrat_date 2020-04-02 Close