Variable charge many-body interatomic potentials
- PDF / 968,900 Bytes
- 9 Pages / 585 x 783 pts Page_size
- 32 Downloads / 172 Views
Introduction Many devices are built from materials with very different atomic structures and involve various types of bonding: covalent, ionic, metallic, and secondary bonding. The analysis of such systems at the atomic level is challenging. Electronic-structure methods, of which techniques based on density functional theory (DFT) are the most prevalent, generally provide high materials fidelity.1 However, because of the large computational load, DFT methods are limited to relatively small system sizes, typically a few hundred atoms. Advances in DFT methods, whose computational cost scales linearly with system size, are increasing this number. Currently, however, DFT methods are generally not able to address many important and topical issues in materials science, particularly those associated with complex microstructures. Alternately, atomic-level simulation methods attempt to describe materials structures using empirical descriptions of the interactions that encapsulate the complex bonding effects of the valence electrons without explicitly describing the electrons themselves. The advantage of these methods is their high computational speed and their ability to probe large systems (millions or even billions of atoms) at finite temperatures and under external driving forces. Of course, the empirical approach usually involves sacrificing some materials fidelity; typically,
however, with a given interatomic potential, it is possible to describe a range of phenomena with at least semi-quantitative precision. Because they describe very different bonding types, empirical potentials for metals, ceramics, and semiconductors generally have very different functional forms. Indeed, it has not generally been possible for empirical methods to describe structures in which more than one bonding type is present. The reactive force field (ReaxFF)2 and charged optimized many-body (COMB)3,4 potential methods are two independently developed platforms for describing complex bonding environments found in real materials. Although different in a large number of details, they are built around the same two fundamental concepts: self-consistent charge equilibration and bond order. A fundamental difference between the COMB and ReaxFF formalisms on the one hand, and most other force fields on the other, is that COMB and ReaxFF do not use fixed connectivity for the chemical bonds. Both COMB3,4 and ReaxFF2 were developed to help bridge the gap between quantum mechanical treatments of atomic forces and the non-reactive interatomic potentials traditionally used in atomic-level simulations (for example, the MM35 and AMBER6 [assisted model building with energy refinement] force fields). Both are reactive force fields and include the
Yun Kyung Shin, Department of Mechanical and Nuclear Engineering, Pennsylvania State University; [email protected] Tzu-Ray Shan, Sandia National Laboratories, Albuquerque, NM; [email protected] Tao Liang, Department of Materials Science and Engineering, University of Florida; liang75@ufl.edu Mark J. Noordhoek, Department of Materials
Data Loading...
