In this work, we carried out theoretical calculations to determine the structure of the hydrogen phosphate anion (HPO₄^2-) in the free state and its structure and position when intercalated between layers of the zinc and aluminum layered double hydroxide [Zn-Al-HPO₄]. We hypothesized that the anion might be intercalated either by forming strong bonds with zinc, or by means of hydrogen bonds with water molecules, and we performed a number of different calculations to determine which of the two hypotheses was correct. We used the DFT B3LYP/6-311G ab initio quantum method to calculate interatomic and interlayer distances, vibration frequencies and enthalpy of formation of the hydrogen phosphate anion in the free state and in the various models proposed, as well as the force constant of the Zn-O bond in the different chemical structures. Results obtained by DFT B3LYP/6-311G were compared to those obtained by experiment and by using the semi-empirical methods AM1 and PM3, and it was shown that results obtained by DFT B3LYP/6-311G correspond more closely to experimental results than those obtained by the two semi-empirical methods. Finally, we established that the hydrogen phosphate anion HPO₄^2- is intercalated between the two layers of the layered double hydroxide [Zn-Al-HPO₄] by means of hydrogen bonds with water molecules, while the phosphate anion PO₄^3- is bound to zinc atoms.

In this work we used the AM1 and PM3 semi-empirical methods, together with density functional theory (DFT) B3LYP 6-311G, to determine the structure and position of the carbonate anion intercalated between layers of the zinc and aluminum layered double hydroxide [Al-Zn-Co3] at ambient temperature. We calculated interlayer distances, vibration frequencies, force constants and enthalpies of formation. We showed that at ambient temperature the CO32- anion is intercalated in the interlayer space by the formation of hydrogen bonds with water molecules. The results obtained using these three methods are compared to those obtained experimentally and those obtained using the Hartree-Fock STO-3G method.