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Determination of Elastic Surface Constants for fcc Materials and their Applications in Nanostructures

Enzevaee, Camelia | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51406 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Mohammadi Shodja, Hossein
  7. Abstract:
  8. This work focuses on developing a theoretical approach for the calculations of the surface elastic constants for (100) planes of fcc crystals. Using this method, the surface elastic constants, as well as the surface residual stress of the (100) planes of Al, Ag, Ni, Pt, and Cu fcc crystals, are evaluated using quantum calculations and VASP code. Surface effects are important in nanostructures and the considered metals are the most applicable ones in nanostructures especially in optic and electronic fields. For verification of the obtained values for surface elastic constants and residual stress, other surface parameters including the equilibrium lattice parameter, the energy per atom of the corresponding bulk, surface energy density, and surface layer relaxation are obtained during the modeling and compared with the available results in the literature. The rest of this work is devoted to the investigation of the importance of considering surface effects in solving problems. To this end, surface effects on the propagation of Love and Rayleigh surface waves in single crystal fcc half-spaces are addressed as the first problem. The crystallographic orientation of the free surface of the half-space which depends on the orientation of the fcc crystals in the bulk is also studied. For this purpose, two different orientations are considered: (1) the free surface of the half-space is (010) plane and the surface waves propagate in [100] direction, ( 2 ) the free surface of the half-space is (110) plane and the surface waves propagate in [110] direction. Next, the critical conditions for the generation of a screw misfit dislocation dipole (MDD) at the interface between a nanowire (NW) and its surrounding unbounded matrix due to misfit strain are investigated within surface/interface elasticity theory and the results are compared with the classical ones
  9. Keywords:
  10. Surface Energy ; Screw Dislocation ; Surface Elasticity ; Sloshing ; Surface Elastic Constants ; Surface Residual Stress ; Surface Layer Relaxation

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