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#DRAWING MOLECULES IN CRYSTALMAKER SOFTWARE#The software comes with a large set of datafiles and can read the XtalDraw datafiles, but it can also read the American Mineralogist Crystal Structure Database data files. The site features images and animations of crystal structures, and the software can be freely downloaded from the site.Point intrinsic and extrinsic defects, especially paramagnetic ions of transition metals and rare-earth elements, have essential influence on properties of lithium niobate, LN and tantalate, LT, and often determine their suitability for numerous applications. #Draw fe crystal in crystalmaker software Discussions about structures of the defects in LN/LT have lasted for decades. Many experimental methods facilitate progress in determining the structures of impurity centers. This paper gives current bird’s eye view on contributions of Electron Paramagnetic Resonance (EPR), and Electron Nuclear Double Resonance (ENDOR) studies to the determination of impurity defect structures in LN and LT crystals for a broad audience of researchers and students. Symmetry and charge compensation considerations restrict a number of possible structures. Comparison of measured angular dependences of ENDOR frequencies with calculated ones for Li and Nb substitution using dipole–dipole approximation allows unambiguously to determine the exact location of paramagnetic impurities. ![]() Models with two lithium vacancies explain angular dependencies of EPR spectra for Me 3+ ions substituting for Li + like Cr, Er, Fe, Gd, Nd, and Yb. Self-compensation of excessive charges through equalization of concentrations of Me 3+(Li +) and Me 3+(Nb 5+) and appearance of interstitial Li + in the structural vacancy near Me 3+(Nb 5+) take place in stoichiometric LN/LT due to lack of intrinsic defects. Point intrinsic and extrinsic defects, especially paramagnetic ions of transition metals and rare-earth elements, belong to the most important defects in lithium niobate (LN, LiNbO 3) and tantalate (LT, LiTaO 3), because of their essential influence on properties of this material, such as domain structure, electro-optical coefficients, light absorption, refractive indices, birth and evolution of wave-front dislocations ( and references there), and their consequences for present and potential applications. A lot of effort was spent to establish a correlation between the observable data and the crystal composition, and to develop experimentally supported models of the defects: ion charges, identities, and position of the ions in the lattice, their nearest surroundings, ways of charge compensation and recharge mechanisms. Discussions about structures of intrinsic and extrinsic defects in LN/LT have lasted for decades. With time, the proposed structures were evolved and detailed.
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