Exploring The Anion Chemical Space: A Model of Electroelastic Material Ln2OF2-xClxH2 (Ln=Y,La,Gd) with High Mechanical Sensitivity and Remarkable Energy Harvesting
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The main result of our investigation is the prediction of a new family of multi-anion compounds - Ln2OF2-xClxH2 (Ln=Y,La,Gd) which due to anomalous elastic behaviour could present interest for the design and development of electromechanical devices. The composition Ln2OF2-xClxH2 utilizes complex heteroatomic anion [OF2-xClxH2]-6; in a solid state, as it follows from the DFT calculations, the system crystallizes into a columnar-type layered structure of P3m1 or R3m trigonal symmetries in which the LnO(F,Cl)H and Ln(F,Cl)FH layers are uniformly stacked in an
alternating order along the high-symmetry c axis. In the trigonal lattice without inversion center, the resulting two-layers geometry puts groups of the anionic species together in a way that gives rise to the strong localization of valence charge density. We showed that being globally stable, such specific crystal architecture may lead to a high asymmetry of mechanical and electrical responses with respect to imposed loads.
Moreover, small dynamic changes of the equilibrium charge and bonding configurations may cause rather the enhanced structural sensitivity of elastic responses at low pressures. Comparison of electromechanical characteristics showed that the predicted materials can serve as direct successors of the line of PVDF piezopolymers.