The geometry, topology and structure of amorphous solids

Abstract

Clusters of atoms can be divided into three categories depending on their topology. One of the categories provides the basis for development of a model of a perfectly random structure (ideal amorphous solid) using the non-equilateral triangle topology in the coordination shell. Metallic glasses solidify as amorphous solids with random arrangement of atoms. A model of Zr-based metallic glass has been constructed and described in terms of cluster topology, and compared with a recently published dynamic molecular model of the same alloy. It is shown that the pair distribution function for the ideal amorphous model relates to the pair correlation function obtained from the dynamic model. Debye X-ray scattering computations reveal the presence of vacancies and other flaws relative to the ideal amorphous solid. A shift in the peak position can be predicted using the Erhenfest formula. Two atomic displacement mechanisms involving a five-atom sub-cluster are identified as the fundamental means of compositional redistribution between clusters in the alloy.

Influence of spatial and temporal coherences on atomic resolution high angle annular dark field imaging

“…To investigate the impact of these amorphous layers on the HAADF-intensity in this manuscript, the theoretical structure of amorphous GaP was determined utilizing the IAS software [32][33][34]. The structures found were used as input for STEM intensity simulations.…”

“…A residual spherical aberration of 2 µmwas Additionally, the intensity of amorphous GaP was simulated. Here a supercell of the same dimensions as for crystalline case was derived by the software to simulate the atomic packing in Ideal Amorphous Solids (IAS) [32][33][34]. This software generates the spherical amorphous structure that satisfies the basic requirements for amorphous solids.…”

Effects of sintering temperature on microstructure and property evolution of Fe81Cu2Nb3Si14 soft magnetic materials fabricated from amorphous melt-spun ribbons by spark plasma sintering technique

“…A slight expansion of sintered compacts at the third stage is possibly attributed to precipitating crystallization products such as α-Fe(Si), Cu and Nb 5 Si 3 phases. It is well known that the amorphous alloys have their unique structure of dense atomic packing and random atomic configuration [23]. Once the crystallization behavior occurs, long-range diffusion and rearrangement of different species of atoms will be necessitated for precipitation of crystalline phases, and then the unique amorphous structure will be destroyed.…”

Geometry and Topology of Structure in Amorphous Solids

“…For the monoatomic IAS, k max = 12, [2] for the IAS with five types of atom k max = 18 (for Zr-inner sphere, Be-outer spheres). [10] Examples of measured distributions for mono-and multi atomic Round Cells based on touching spheres, are shown in Figure 4. A formula for the coordination number distribution, based on combinatorics, had been proposed by Fu¨rth, [11] and used by the authors to analyze the data for monoatomic and multiatomic IAS with mixed success.…”