Valence Force Field for Layered Double Hydroxide Materials Based on the Parameterization of Octahedrally Coordinated Metal Cations

Abstract

A valence force field named LDHFF was systematically developed for the layered double hydroxide (LDH) materials. Its potential function was referred from the polymer consistent force field (PCFF) by introducing a double-well potential to describe the oxygen–metal–oxygen (O–M–O) bending in the octahedral host sheets. The bonded (intramolecular) parameters, including the bond stretching constants, angle bending coefficients, as well as cross terms, were obtained from density function theory (DFT) calculations on the simplified but representative cluster models [MII2MIII(OH2)9(OH)4]3+ and [MIII3(OH2)9(OH)4]5+ (MII2MIII = Mg2Al, Zn2Al, Co2Al, Ni2Al, Cu2Al, Mg2Fe, Zn2Fe, Ni2Fe, Mg2Cr, Zn2Cr, Cu2Cr, Co2Cr; MIII = Al, Fe, Cr). In the case of nonbonded potential, the van der Waals parameters were obtained by fitting them to the cluster models mentioned above. The partial charges used to calculate the Coulombic interactions were assigned as Mulliken charge from density functional theory (DFT) calculation. To validate these potential parameters, a series of molecular dynamics (MD) simulations were subsequently employed for 24 LDH models, and the resulting structures, vibrational frequencies, as well as binding energies are in high accordance with the experimental findings. Using LDHFF, stable octahedral host structures were maintained over 2 ns in molecular dynamics simulations. These results demonstrate that LDHFF works effectively and accurately for MD studies of LDH materials, which provides a theoretical insight for understanding the structural property and exploiting the fabrication of functional LDH and related materials.