Size effect on atomic structure in low-dimensional Cu-Zr amorphous systems

Abstract

The size effect on atomic structure of a Cu64Zr36 amorphous system, including zero-dimensional small-size amorphous particles (SSAPs) and two-dimensional small-size amorphous films (SSAFs) together with bulk sample was investigated by molecular dynamics simulations. We revealed that sample size strongly affects local atomic structure in both Cu64Zr36 SSAPs and SSAFs, which are composed of core and shell (surface) components. Compared with core component, the shell component of SSAPs has lower average coordination number and average bond length, higher degree of ordering, and lower packing density due to the segregation of Cu atoms on the shell of Cu64Zr36 SSAPs. These atomic structure differences in SSAPs with various sizes result in different glass transition temperatures, in which the glass transition temperature for the shell component is found to be 577 K, which is much lower than 910 K for the core component. We further extended the size effect on the structure and glasses transition temperature to Cu64Zr36 SSAFs, and revealed that the T g decreases when SSAFs becomes thinner due to the following factors: different dynamic motion (mean square displacement), different density of core and surface and Cu segregation on the surface of SSAFs. The obtained results here are different from the results for the size effect on atomic structure of nanometer-sized crystalline metallic alloys.

Atomic Structure and Magnetic Properties of the Fe78B13Si9 Amorphous Alloy Surface

“…However, it is inappropriate for the surface of the bulk materials and twodimensional slabs in the simulation. Therefore, the developed PCF is adopted herein, 11 which is defined by the following equation…”

“…There are two ways to estimate the thickness of the surface component for the low-dimensional amorphous systems: one is based on the composition variation along the thickness direction for the two-dimensional amorphous films, and the other one is defined by the first valley in the PCF for the zerodimensional amorphous particles. 11 The composition can be calculated by subdividing the slab into smaller slabs and counting the number of atoms within each subdivision. The composition variation is not enough to exactly determine the thickness of the surface component of the Fe 78 B 13 Si 9 slab because the composition variation is dramatic, resulting from only 200 atoms in the Fe 78 B 13 Si 9 slab.…”

“…Using the first valley is not an unreasonable value from the atomic packing short-range order point of view. 11,22 The composition variation of Fe along the Z-axis (thickness direction) is shown in Figure 1a. It can be seen that the Fe content obviously deviates from the nominal composition in the surface with a length of about 3 Å.…”

Approaches for Long Lifetime Organic Light Emitting Diodes

“…The key element in fabricating a high performance and long lifetime tandem device is the connecting materials stack, which plays a significant role in the electric field distribution, charge generation and charge injection mechanism. [ 3,271,272 ]…”

The critical model size for simulating the structure-dynamics correlation in bulk metallic glasses

“…It indicates that although the static structure scarcely shows a system size-dependence, the dynamical behaviors, such as the atomic mobility, the transient hydrodynamics, and structural relaxation, in a finite-size system manifest apparent deviation from those of larger systems. For MGs, the previous simulation studies [25,26] concentrated on the size effect in lowdimensional metallic liquids and glasses. It was found that the loosely packed, liquid-like surface layers with faster dynamics play a dominant role in the strong size dependence of the atomic structure, dynamics, and glass transition temperature in low-dimensional MGs.…”