An Interatomic Potential for Studying CuZr Bulk Metallic Glasses

Abstract

Binary alloys capable of forming metallic glasses have been discovered recently. [1][2][3][4][5][6][7][8] The mechanical properties of BMGs are remarkably different from the ones of ordinary metallic alloys due to the atomic level disorder in the glassy state. Unlike crystalline materials plastic deformation in metallic glasses cannot be caused by lattice defects but takes place through atomic-scale deformation events and may furthermore involve localization through formation of shear bands. For understanding the origin of their mechanical properties it is important to get the basic understanding of fundamental theoretical problems through atomistic simulations.Molecular dynamics (MD) treats atomic systems according to Newtonian mechanic laws. Atoms are point particles, interacting through an interatomic potential, describing the energy of an atom as a function of the positions of all atoms in a neighboring region of space. The time evolution of the system is obtained by numerically integrating Newton's second law. Often the interatomic potential is a classical potential, no quantum mechanical description of the material is attempted, but the functional form of the potential may be derived from quantum mechanical arguments. [9] MD is able to treat systems with millions of atoms, and permits the average calculations of transport (diffusion, thermal conductivities, viscosity), or mechanical quantities (elastic constant, plastic yield), and also the modeling of complex phenomena (shear band localization, fracture appearance, neutronic cascades).The quality of the results will depend on the quality of the interatomic potential, simple potentials giving a less accurate description of the interatomic interactions while allowing very large simulations, more complicated potentials may give a better description of the interaction, but limit the simulation size. Many-body potentials such as the Embedded Atom Method [10] and the Effective Medium Theory (EMT) [11,12] have been shown to give a good description of the late transition metals crystallizing in close-packed structures, and their alloys, while still allowing simulations with millions of atoms. [13] In this paper, we create an EMT potential optimized for modeling the mechanical and thermodynamic properties of CuZr bulk metallic glass.CuZr was recently discovered to be a binary bulk metallic glass. [6,14] Since binary alloys are easier to model than alloys with more elements, this makes CuZr an attractive bulk metallic glass to study theoretically. Previously, an interatomic force field has been fitted to CuZr by Duan et al., [28] but we find that the EMT force field described here provides a better description of the structure of the metallic glass. The potential developed here will be used to model the mechanical properties of CuZr, to be published elsewhere. Fitting an Effective Medium Theory PotentialThe functional form of EMT is described by Jacobsen et al. [11] and will not be repeated here, as it is rather complex. The energy of each atoms is the sum of two te...

Atomic structure of shear bands in Cu64Zr36 metallic glasses studied by molecular dynamics simulations

“…The inset shows an example of the typical 3D atomic configuration of amorphous Cu 64 Zr 36 . This study illustrated that the nearest average interatomic distances of the Cu-Cu (r Cu-Cu = 2.48 Å), Cu-Zr (r Cu-Zr = 2.82 Å), and Zr-Zr (r Zr-Zr = 3.16 Å) pairs agreed reasonably well with the experimental measurements (r Cu-Cu = 2.48 Å, r Cu-Zr = 2.72 Å, and r Zr-Zr = 3.12 Å) and simulations (r Cu-Cu = 2.58 Å, r Cu-Zr = 2.80 Å, and r Zr-Zr = 3.21 Å) [34][35][36][37][38][39][40][41][42]. These results support the reliability of the EAM potential used in this study to describe the atomic structures of actual MGs [43].…”

Molecular dynamics simulations of clusters and thin film growth in the context of plasma sputtering deposition

“…As an example, ZrCu alloys have attracted interest in recent years, due to their bulk metallic glass properties (Cheng, 2011;Wang, 2004;Yu, 2006;Pǎduraru, 2007;Mei-Bo, 2004), and as amorphous alloy films for their mechanical (Xu, 2004;Musil, 2003;Das, 2005) and superconductivity properties (Karpe, 1996). Dudonis et al (Dudonis, 1996) prepared thin films with Zr composition in the range of (5 ≤ x ≤ 95) by using high working power (490 W and 1380 W on Cu and Zr targets, respectively) during magnetron sputter deposition.…”

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“…The parameterization procedure of the EOS follows a similar strategy to that of Paduraru et al (2007). The target parameters are those determined by Leu et al (1975) and are optimized in order to minimize simultaneously the quadratic error on the melting curve of MgO and the …”