Ab initio based polarizable force field generation and application to liquid silica and magnesia

Abstract

We extend the program potfit, which generates effective atomic interaction potentials from ab initio data, to electrostatic interactions and induced dipoles. The potential parametrization algorithm uses the Wolf direct, pairwise summation method with spherical truncation. The polarizability of oxygen atoms is modeled with the Tangney-Scandolo interatomic force field approach. Due to the Wolf summation, the computational effort in simulation scales linearly in the number of particles, despite the presence of electrostatic interactions. Thus, this model allows to perform large-scale molecular dynamics simulations of metal oxides with realistic potentials. Details of the implementation are given, and the generation of potentials for SiO(2) and MgO is demonstrated. The approach is validated by simulations of microstructural, thermodynamic, and vibrational properties of liquid silica and magnesia.

Simulation of crack propagation in alumina with ab initio based polarizable force field

“…This means that for small magnitudes of the wave vectors k, the charge structure factor is also small. In previous studies 16,23 it was shown that the reciprocal-space term is indeed negligible compared to the real-space part, provided that the splitting parameter κ is chosen small enough. As however a smaller κ results in a larger real-space cutoff r c , the latter has to be chosen three or four times the size of a typical shortrange cutoff radius in metals.…”

“…As however a smaller κ results in a larger real-space cutoff r c , the latter has to be chosen three or four times the size of a typical shortrange cutoff radius in metals. In a recent study 16 a cutoff radius of only 8Å was sufficient to describe the electrostatics of liquid silica and magnesia accurately. In addition, a continuous and smooth cutoff of the remaining screened Coulomb potentialẼ qq (r ij ) = q i q j erfc(κr ij )r −1 ij is adopted at r c by shifting the potential so that it goes to zero smoothly in the first two derivatives at r = r c .…”

“…For more information about the implementation of long-range electrostatic interactions including the TS force field with Wolf summation see Ref. 16.…”

“…However, for SiO 2 14-16 and MgO, 16 it was shown that an accurate description can be achieved without angular dependent terms, but with polarizable oxygen atoms. There, the potential model of Tangney and Scandolo 14 (TS) is applied, in which the dipole moments of oxygen atoms are determined self-consistently from the local electric field of surrounding charges and dipoles.…”

“…16, the computational effort in simulations scales linearly in the number of particles, which is due to the Wolf summation. 17 We apply this combination of the TS model and the Wolf summation method in the potential generation as well as in simulations.…”