Phonon spectrum and related thermodynamic properties of microcrack in bcc-Fe |
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Authors: | Cao Li-Xia and Wang Chong-Yu |
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Institution: | Central Iron and Steel Research Institute, Beijing 100081, China; International Centre for Materials Physics, Chinese Academy of Sciences, Shenyang 110016, China; Department of Physics, Tsinghua University, Beijing 100084, China |
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Abstract: | The phonon spectrum and the related thermodynamic properties of
microcracks in bcc-Fe are studied with the recursion method by using
the Finnis--Sinclair
(F--S) N-body potential. The initial configuration of the microcracks is established
from an anisotropic linear elastic solution and relaxed to an
equilibrium by molecular dynamics method. It is shown that the local
vibrational density of states of the atoms near a crack tip is
considerably different from the bulk phonon spectrum, which is
closely associated with the local stress field around the crack tip;
meanwhile, the local vibrational energies of atoms near the crack
tip are higher than those of atoms in a perfect crystal. These
results imply that the crack tip zone is in a complex stress state
and closely related to the structure evolution of cracks. It is also
found that the phonon excitation is a kind of local effect induced
by microcracks. In addition, the microcrack system has a higher
vibrational entropy, which reflects the character of phonon spectrum
related to the stress field induced by cracks. |
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Keywords: | phonons microcrack metals |
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