A molecular dynamics framework to explore the structure and dynamics of layered double hydroxides

abstract

It is presented a straightforward procedure based on the CLAYFF force field to perform molecular dynamics (MD) computer simulations with the GROMACS open source package of layered double hydroxide (LDH) materials with different intercalated anions. This procedure enables running very long simulations of systems where all atomic positions are allowed to move freely, while maintaining the integrity of the LDH structure intact. Therefore, it has the potential to model different important applications of LDH involving ion-exchange and interlayer equilibrium processes in diverse areas as drug delivery, water purification, and corrosion protection. The magnesium-aluminium based LDH with a metallic ratio 2:1 (Mg2Al) was chosen to validate our computer simulation framework, because of the comprehensive experimental and computational studies reported in the literature devoted to the understanding of the structure of Mg2Al LDH. Potential parameters from the literature were used to model the Mg2Al LDH with different intercalated anions using a new set of atomic point charges calculated with the DDEC6 formalism. Once the model was validated through careful comparisons of the simulated and experimental structures, the procedure was adapted to the Zn2Al LDH materials. Lennard-Jones parameters had to be developed for zinc (II) cations and calibrated using the experimental structural data found in the literature for Zn2Al LDH and the height of the galleries determined experimentally in this work for Zn2Al with intercalated nitrate anions. The consistency of the model is proved by carrying out MD simulations to reproduce in the computer the typical experimental conditions in which the Zn2Al LDH is immersed in a sodium chloride water solution to act as a nanotrap for aggressive anions in corrosion protection applications. The LDH structure is maintained in the MD simulation in which the LDH is free to move alongside the solution and allowing a natural anion exchange between the LDH and the solution as well as dehydration/hydration of the basal space.

keywords

HYDROTALCITE-LIKE COMPOUNDS; TOTAL-ENERGY CALCULATIONS; X-RAY-DIFFRACTION; WAVE BASIS-SET; AB-INITIO; INTERLAYER ANIONS; CRYSTAL-CHEMISTRY; FORCE-FIELD; INTERCALATION; SIMULATIONS

subject category

Chemistry; Materials Science; Mineralogy

authors

Perez-Sanchez, G; Galvao, TLP; Tedim, J; Gomes, JRB

Groups

G3 - Electrochemical Materials, Interfaces and Coatings
G6 - Virtual Materials and Artificial Intelligence

Projects

CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013)

Unveiling the self-healing mechanisms associated with smart nanocontainers (SELMA)

acknowledgements

This work was developed in the scope of project CICECO - Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (Ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement, and in the framework of project SELMAP2020-PTDC/QEQ-QFI/4719/2014, funded by Project 3599 - Promover a Producao Cientifica e Desenvolvimento Tecnologico e a Constituicao de Redes Tematicas (3599-PPCDT) and FEDER funds through COMPETE 2020, Programa Operacional Competitividade e Internacionalizacao (POCI). The authors also thank financial support from FCT (Programa Investigador FCT). JT thanks FCT for the research grant IF/00347/2013.