Mechanical Properties of Single Crystal Diamond Estimated by Molecular Dynamics Simulation with the Second-Generation RE
- PDF / 789,773 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 103 Downloads / 208 Views
Mechanical Properties of Single Crystal Diamond Estimated by Molecular Dynamics Simulation with the Second-Generation REBO Potential Shingo Okamoto1 and Akihiko Ito1,2 1 Mechanical Engineering Course, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan 2 Composite Materials Research Laboratories, Toray Industries, Inc., Masaki-cho 791-3193, Japan ABSTRACT We investigated the effects of tensile direction and periodic boundary condition (PBC) on the mechanical properties of single crystal diamond (SCD) under tensile loading, using MD simulations with the second-generation reactive empirical bond order (REBO) potential. We found that when the Poisson’s ratio is assumed to be constant under the canonical (NVT) ensemble and the PBC is applied to all directions of X, Y, and Z, each qualitative relation between a mechanical property such as tensile strength or Young's modulus and the tensile direction is in agreement with both the results calculated by the first principle and by the cleavage energy method. In addition, we found that when the PBC is applied only to the Y direction under the NVT ensemble, each qualitative relation between a mechanical property and the tensile directions is in agreement with the MD results using the Tersoff potential. Our results indicate that the second-generation REBO potential is also useful for MD simulations on the tension of diamond. INTRODUCTION Carbon materials such as diamond, carbon nanotubes, graphene, or fullerene have complex atomic structures and variable modes of covalent bonding. It is important to use an appropriate potential function in order to express their physical properties in molecular dynamics (MD) simulations. The second-generation reactive empirical bond order (REBO) potential has been mainly used in simulations of carbon nanotubes and graphite, which are composed of sp2 carbon atoms [1,2]. The second-generation REBO potential may also be able to simulate the basic physical properties of diamond, which is composed of sp3 carbon atoms, in addition to its bond length, bond energy, elastic constants, vacancy formation energy, and so on, more exactly than other potential functions [3,4]. In the present paper, MD simulations on the tension of single crystal diamond (SCD) were performed with the second-generation REBO potential to investigate the effects of tensile direction and periodic boundary condition (PBC) on the tensile strength and Young’s modulus. The utility of the potential was investigated by comparing the results to those of previous studies with the Tersoff potential [5] and the density functional theory (DFT) method [6]. METHOD The second-generation REBO potential is shown in eq. (1).
[
]
EREBO = ∑∑ VR (rij )－Bij*VA (rij ) i
j >i
(1)
The terms VR(rij) and VA(rij) represent pair-additive interactions that reflect interatomic repulsions and attractions, respectively. In this study, two types of analysis model are used: the PBC model and the non-PBC model. The PBC models for (100), (110), and (111) tensions are rectan
Data Loading...
