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**Search for:**surface-elastic-constants

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

, Ph.D. Dissertation Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract

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...

#### Axisymmetric response of a bi-material full-space reinforced by an interfacial thin film

, Article International Journal of Solids and Structures ; Volume 90 , July , 2016 , Pages 251–260 ; 00207683 (ISSN) ; Samea, P ; Eskandari, M ; Sharif University of Technology
Elsevier Ltd
2016

Abstract

Analytical treatment of a linear elastic isotropic bi-material full-space reinforced by an interfacial thin film under axisymmetric normal loading is addressed. The thin film is modeled as an extensible membrane perfectly bonded to the half-spaces. By virtue of Love's potential function and Hankel integral transform, elastic fields of the system are explicitly written in the form of semi-infinite line integrals. The analytical results are verified by the special cases corresponding to the surface stiffened half-space and classical bi-material problem. The limiting cases of reinforced homogeneous full-space and inextensible membrane are presented and discussed. The proposed formulation is...

#### Surface elasticity revisited in the context of second strain gradient theory

, Article Mechanics of Materials ; Volume 93 , 2016 , Pages 220-237 ; 01676636 (ISSN) ; Shodja, H. M ; Sharif University of Technology
Elsevier

Abstract

Surface/interface stresses, when notable, are closely associated with a surface/interface layer in which the interatomic bond lengths and charge density distribution differ remarkably from those of the bulk. The presence of such topographical defects as edges and corners amplifies the noted phenomena by large amounts. If the principal features of interest are such studies as the physics and mechanics of evolving microscopic-/nanoscopic-interfaces and the behavior of nano-sized structures which have a very large surface-to-volume ratio, traditional continuum theories cease to hold. It is for the treatment of such problems that augmented continuum approaches like second strain gradient and...

#### Determination of surface properties and elastic constants of FCC metals: A comparison among different EAM potentials in thin film and bulk scale

, Article Materials Research Express ; Volume 6, Issue 1 , 2019 ; 20531591 (ISSN) ; Yousefi, F. S ; Taghibakhshi, A ; Sharif University of Technology
Institute of Physics Publishing
2019

Abstract

Three independent elastic constants C 11, C 12, and C 44 were calculated and compared using available potentials of eight different metals with FCC crystal structure; Gold, Silver, Copper, Nickel, Platinum, Palladium, Aluminum and Lead. In order to calculate the elastic constants, the second derivative of the energy density of each system was calculated with respect to different directions of strains. Each set of the elastic constants of the metals in bulk scale was compared with experimental results, and the average relative error was for each was calculated and compared with other available potentials. Then, using the Voigt-Reuss-Hill method, approximated values for Young and shear moduli...

#### A combined first principles and analytical treatment for determination of the surface elastic constants: Application to Si(001) ideal and reconstructed surfaces

, Article Philosophical Magazine Letters ; Volume 92, Issue 1 , Sep , 2012 , Pages 7-19 ; 09500839 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2012

Abstract

Behavior of nanostructures, which are characterized by a large surface-to-volume ratio, is greatly influenced by their surface parameters, such as surface elastic moduli tensor. Accurate determination of the surface elastic constants by first principles is of particular interest. To this end, through consideration of the fundamental thermodynamic arguments for free solid surfaces, an analytical formulation for the change in specific Helmholtz surface free energy is developed. Relating this formulation to the corresponding energy calculated via first principles leads to the determination of the surface elastic moduli tensor. The surface mechanical properties, namely surface energy, surface...

#### Characterization of silicon surface elastic constants based on different interatomic potentials

, Article Thin Solid Films ; Volume 626 , 2017 , Pages 104-109 ; 00406090 (ISSN) ; Rezaei, S ; Sharif University of Technology
Abstract

Mechanical properties of materials are an important factor in designing nanoscale systems. Several researches and experiments have shown that the mechanical properties of the nano-scale materials are different from those of bulk. One of the major reasons for this difference is that the ratio of surface to volume increases at the nano-scale, and the effects of free surfaces become very important. In this paper, we have measured the surface elastic constants of silicon crystalline structure using different interatomic potentials. The potentials employed here are EDIP (Environment-Dependent Interatomic Potential), Stillinger-Weber and Tersoff, and also different crystalline orientations are...

#### Surface characterization of face-centered cubic crystals

, Article Mechanics of Materials ; Volume 129 , 2019 , Pages 15-22 ; 01676636 (ISSN) ; Enzevaee, C ; Sharif University of Technology
Elsevier B.V
2019

Abstract

To date, the examination of surface energy and surface layer relaxation has been the subject of several experimental and simulation works, whereas evaluation of surface residual stresses and surface elastic constants has received very little attention. In addition to the fundamental importance of these properties in the understanding of such phenomena as crystal equilibrium shape, surface roughening and segregation, they are also crucial for use in the theoretical studies based on continuum theory of elastic material surfaces. This work focuses on developing a theoretical approach for the calculations of the surface residual stress and surface elastic constants for (100) planes of fcc...

#### Surface characterization of face-centered cubic crystals

, Article Mechanics of Materials ; Volume 129 , 2019 , Pages 15-22 ; 01676636 (ISSN) ; Enzevaee, C ; Sharif University of Technology
Elsevier B.V
2019

Abstract

To date, the examination of surface energy and surface layer relaxation has been the subject of several experimental and simulation works, whereas evaluation of surface residual stresses and surface elastic constants has received very little attention. In addition to the fundamental importance of these properties in the understanding of such phenomena as crystal equilibrium shape, surface roughening and segregation, they are also crucial for use in the theoretical studies based on continuum theory of elastic material surfaces. This work focuses on developing a theoretical approach for the calculations of the surface residual stress and surface elastic constants for (100) planes of fcc...

#### Surface and interface effects on torsion of eccentrically two-phase fcc circular nanorods: Determination of the surface/interface elastic properties via an atomistic approach

, Article Journal of Applied Mechanics, Transactions ASME ; Volume 78, Issue 1 , October , 2011 , Pages 0110111-01101111 ; 00218936 (ISSN) ; Shodja, H. M ; Sharif University of Technology
2011

Abstract

The effect of surface and interface elasticity in the analysis of the Saint-Venant torsion problem of an eccentrically two-phase fcc circular nanorod is considered; description of the behavior of such a small structure via usual classical theories cease to hold. In this work, the problem is formulated in the context of the surface/interface elasticity. For a rigorous solution of the proposed problem, conformal mapping with a Laurent series expansion are employed together. The numerical results well illustrate that the torsional rigidity and stress distribution corresponding to such nanosized structural elements are significantly affected by the size. In order to employ surface and interface...