Microstructure and Jahn-Teller Effect of Cu-Zn-Mg-Al Layered Double Hydroxides

We propose a periodic interaction model for layered double hydroxides, CuZnMgAl quaternary hydrotalcites [(M)-IV-LDHs (M=Cu, Zn, Mg, Al)]. Based on density functional theory the geometries of CuZnMgAl quaternary hydrotalcites were optimized using the CASTEP program. The impacts of the Jahn-Teller effect and the location of chlorine over the layer distortion and stability were investigated by analyzing the geometric parameters, the electronic arrangement, charge populations, binding energies, and hydrogen-bonding. The optimization results showed that the Jahn-Teller effect does not only exist in Cu2+ when its d orbital is partially filled but it also exists in Zn2+ when its d orbital is full as well as in Mg2+ when its p orbital is partially filled. Systems where the chloride is located above the metal show greater metal distortion than systems with anions located above non-metals. Eight systems (Nos. 1-8) were chosen for our work and their absolute binding energy values were found to decrease gradually while the stability of the systems became worse. Finally, the systems became unstable and were found to be flattened octahedral forms. These results help us to better understand the Jahn-Teller effect in copper-containing IV-LDHs from theory.