Evaluation and Extension of the ReaxFF Reactive Force Field Method for Applications to Dielectric Oxides and their Multi-Material Interfaces
Abstract
Pennsylvania State University Grant #: FA9451-16-1-0041 “Evaluation and extension of the ReaxFF reactive force field method for applications to dielectric oxides and their multi-material interfaces” Abstract Ferroelectric phase transitions of perovskite-based oxides represent an important class of structural phase transitions that have significant technological implications related to piezoelectric and pyroelectric respons. Ferroelectric perovskites exhibit a spontaneous electric polarization that can be reoriented by an external electric field. To improve our understanding of the dielectric properties of the oxides and their interfaces, we need to obtain detailed, atomistic-scale insight in the key events at this interface. Given typical operation conditions include elevated temperatures and relatively long time-scales, a simulation tool is required that can evaluate dynamics and properly describe reaction barriers and reaction energies. Furthermore, defects and domain boundaries in the oxide materials will play a key role in their dielectric response – which means that relatively large systems will need to be used in the simulations so that such large structural features can be considered. This combination of system size and dynamics indicates that quantum mechanical (QM) based methods by themselves will not be sufficient to fully evaluate the activity of a catalyst. While QM-based methods have become key tools in the evaluation of reaction barriers and reaction energies, the high computational cost associated with these methods renders QM-based dynamical descriptions only viable for relatively small systems and short time scales. For a fully dynamical description of events at piezoelectric metal oxide interfaces and boundaries, we require a computational method that is a number of magnitudes faster but retains the quality of QM-results for reaction energetics. Force field (FF) based approaches can provide the computational speed required to perform molecular dynamics (MD) simulations on system sizes sufficiently large to describe the full chemistry of the metaloxide and their interfaces. For this reason, a number of FF-based concepts related to ferroelectric materials have been formulated Beyond these relatively simple – and relatively fast – force field approaches there also exist more sophisticated force field approaches that allow charge flow through polarizable. These concepts all share a significant lack of transferability – they have demonstrated success within a single ferroelectric formulation, but cannot be straightforwardly extended to study interactions of ferroelectic materials in multi-material interfaces – for example, a ferroelectric nanocluster on a metal support, or ferroelectric clusters suspended in an organic polymer. In this proposal, we seek to determine the ability of the ReaxFF method – which shares many features with the COMB potential and has demonstrated transferability to a wide range of materials – for describing ferroelectric material response. We also propose extension of the current ReaxFF model to include an explicit electron/hole – thus introducing an atomic dipole, which is likely to improve the ReaxFF ferroelectric capability.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 15, 2016
- Source ID
- FA94511610041
Entities
People
- Adrianus Van Duin
Organizations
- Air Force Research Laboratory
- Pennsylvania State University
- United States Air Force