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Theory and Modeling of Atomic Arrangements in Metallic Glasses
Zbigniew H. Stachurski
Research School of Engineering, CECS, Australian National University, Canberra ACT
0200, Australia
e: [email protected]
Abstract
The understanding of the atomic-scale structure of solids began with the concept
of translational symmetry, and has to a large degree come about because of the
methods of X-ray crystallography. Theory of crystallography provides a datum from
which the ideal atomic arrangements (and defects) in real materials can be
determined. By comparison, no such universal laws or rules are well known for the
atomic structure in amorphous solids, and for this reason we advance and promote
the theoretical concept of an ideal amorphous solid (IAS) as a partial solution to this
enigma. It will be shown that the IAS model provides an unambiguous basis for the
understanding of atomic arrangements in metallic glasses.
Metallic glasses solidify as amorphous solids with random arrangement of atoms. This
is evidenced by direct experimental techniques, such as HRTEM, XRD, Atomic Probe,
EXAFS, Raman and other. As real materials, BMGs contain imperfections in their
random atomic structure. In order to describe these imperfections a reference state
must be defined first (i.e., the IAS), and appropriate measures must be used to
quantify these. It will be shown that taking the IAS model as the reference state,
imperfections can be defined and their effects evaluated. In particular, it will be shown
how:
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IAS can be used in deformation and fracture mechanics; detailed elastic,
anelastic and plastic deformation mechanisms can be defined and used to
predict deformation (as with dislocation, twinning and point defects motions in
crystalline materials)
IAS can be used in shear band propagation and instability by identifying the
local cluster compositional deviations and instabilities
IAS can be used to predict magnetic, electric, thermal and chemical properties
by means of the aggregate theory
IAS can be used to analyze the developments of nano-crystallinity
IAS can be used in molecular dynamic modeling as the starting cell, thus not
requiring pre-processing to equilibrate the structure and therefore saving
significant run-time
IAS can be used in design of new BMGs