Implementation and Application of the Response EAM for HCP Metals

Atomistic simulations are a powerful tool for the study of materials, especially in the determination of underlying atomistic mechanisms. Molecular dynamics (MD) is an atomistic simulation method that is well suited for a large number of atoms in a system, up to one billion. MD holds sufficient physical rigor while keeping the number of calculations reasonable for modern computational power. In molecular dynamics, a mathematical potential is used to capture the physics of the interaction between two adjacent atoms or molecules. Existing potentials fail to adequately represent the interaction between some materials, such as Magnesium and Titanium, or are based off of non-physics based parameter fitting which suffers from a lack of rigor. For example, the potentials cannot accurately represent electron density distribution and therefore cannot properly replicate elastic constants and surface relaxation in Hexagonal close packed (HCP) materials and some Face centered Cubic Materials (FCC). In this work, we first review the past 30 years of progress in atomistic simulation, more specifically molecular dynamics, discuss the issues with the existing interatomic potentials, and then establish the need for a new response interatomic potential, or the R-EAM. The R-EAM is based on an approximate form of quantum mechanics theory and is an extension of the existing Embedded Atom Model (EAM) potential. Further, we go on to show simulations to confirm the R-EAM by examining dislocation motion in Magnesium nanorods under tension. The ̅ ̅ dislocation (10-12)[10-11] is found in the HCP material, Magnesium, in accordance with experiments. Further implementation of R-EAM should allow for great expansion of molecular vii dynamics because of its increased accuracy in reproducing surface relaxation and dislocation dynamics for HCP and FCC metals.