Thermal expansion, diffusion and melting of Li₂O using a compact forcefield derived fromab initiomolecular dynamics

Abstract

This work shows a straightforward procedure to derive forcefields (FFs) which are able to describe the structural, thermal and transport properties of condensed phases. The approach is based on ab initio molecular dynamics trajectories and an empirical calibration such as the melting point. This is demonstrated for lithium oxide using a Buckingham-type potential and optimized effective atomic charges. The present FF reproduces the density and thermal expansion of Li2O very well, including an anomaly related to the known superionic behaviour, i.e. a pre-melting of the Li sublattice at a critical temperature of Tc = 1200 K. Calculations of the diffusion coefficient as a function of temperature show a strong dependence on vacancy concentration for temperatures below Tc, consistent with previous simulations. Extensions to other ionic systems and compositions are made straightforward by the compact form of the FF and the present methodology employed in the parameter fitting.

Ion Diffusivity through the Solid Electrolyte Interphase in Lithium-Ion Batteries

“…49,[85][86][87][88][89][90][91][92][93][94][95][96] Most of these works focused on developing and evaluating force field parameters for molecular dynamics simulations, which were then used to analyze structure, physical properties, and diffusion. [85][86][87][88][89][90][91][92][93][94] Experimentally, diffusion of Li + in Li 2 O was studied by Oishi et. al 95 using mass spectrometry and the 6 Li radioisotope as a tracer.…”

Ion Hopping and Constrained Li Diffusion Pathways in the Superionic State of Antifluorite Li2O

“…In this work, we use classical atomistic simulations to investigate the spatiotemporal dynamics of Li ions in the superionic state of Li 2 O. We select a rigid-ion, two-body Buckingham-type potential developed by Asahi et al [24] from first principles electronic structure simulations. The potential takes the following form:…”

“…The first term in Equation (1) represents the Coulombic interaction between the charged ions, while the second and third terms represent the repulsive interaction due to the overlap of the electron clouds and the attractive van der Waals or dispersion interaction, respectively. In the parametrization used by Asahi et al [24], the dispersion forces are excluded for all ion-pairs, while the short-range repulsive interaction is attributed to Li-O pair only. It is interesting to note that the training set for developing the potential is mainly driven by the melting point for Li 2 O (T m = 1711 K).…”

Molecular Level Characterization of the Structure and Interactions in Peptide‐Functionalized Metal–Organic Frameworks

“…[16][17][18][19] A more detailed description of the fitting procedures ( Figure S2), capabilities and methods related to this module can be found in the study of France-Lanord et al 17 The same module was successfully applied in other studies. [18][19] For each frame obtained from the AIMD simulations, total potential energy, forces along x, y, and z for each atom, and stress along x, y, and z are recorded. However, only atomic forces were used in the current forcefield parameters optimization.…”

“…[17][18][19] Due to the limited number of parameters to optimize, each one was individually fitted iteratively through mean-square minimization of the forces computed with VASP (from the training set) and LAMMPS. First, we optimized the equilibrium bond distance or angle, followed by optimization of the force constant.…”