On the theory of interaction potentials in ionic crystals

• Published in: Journal of physics. Conference series Vol. 134; no. 1; p. 012025
• Main Authors: Acevedo, Roberto, Soto-Bubert, Andrés
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.11.2008
• Subjects: Convergence; Energy value; Heat of formation; Ionic crystals; Physics
• ISSN: 1742-6596; 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/134/1/012025

The aim of this research work is to report a more comprehensive and detailed study of both, the intermolecular and intramolecular potencial functions with reference to the various families of the elpasolite type crystals. The cohesive energy has been thought as a sum of three terms; the long range (Coulombic), the Born and the van der Waals contributions to the total energy. The Born-Mayer-Buckingham potential1 has been employed in all of these current studies and a number of convergence tests are analyzed from a formal viewpoint. Our work has been focused to the following systems: Cs2NaLnF6, Cs2NaLnCl6, Cs2NaLnBr6, Rb2NaLnF6 and Cs2KLnF6 in the Fm3m space group. A substantial amount of theoretical models have been analyzed and several computing simulations have been undertaken to estimate the reticular energies and the corresponding heat of formation for these crystals. To achieve this goal, a Born-Haber thermodynamic cycle has been introduced in our model. It is shown that the calculated energy values are reasonable and follow the expected trend along the lanthanide series in the periodic chart. We also discuss the advantages and disadvantages of the current and proposed generalized model. The most likely sources for improvement are discussed in detail. New convergence tests as well as some master equations have been introduced to study the various diagonal contributions to the total energy.