First-Principles Study on the Ideal Strengths of Typical Hcp Metals

2012 ◽  
Vol 476-478 ◽  
pp. 2523-2529 ◽  
Author(s):  
Lin Fu ◽  
Quan Zhang ◽  
Bi Yu Tang
Keyword(s):  
Shear Stress ◽  
Electronic Structure ◽  
Transition Metals ◽  
First Principles ◽  
Basal Plane ◽  
Prismatic Plane ◽  
Stress Strain ◽  
Peak Shear Stress ◽  
Theoretical Results ◽  
The Ideal

The ideal strengths of several hcp metals (Be, Mg, Ti, Zn, Y, Zr and Ru) have been investigated by first-principles stress–strain calculations. The results reveal that the ideal shear strengths of these hcp metals occur mainly on basal plane or prismatic plane. Particularly, for basal plane the peak shear stress in direction is smaller than that in direction. The calculated tensile strengths and elongations in direction are broadly consistent with the available theoretical results. Furthermore, both the ideal shear and tension strengths become stronger with the decreasing of c/a for these simple metals or transition metals. The calculated electronic structure further reveals the inherent mechanism of hcp metals.

scholarly journals Correlations of Equilibrium Properties and Electronic Structure of Pure Metals

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2932
Author(s):  
Jianhong Dai ◽  
Dongye He ◽  
Yan Song
Keyword(s):  
Electronic Structure ◽  
Transition Metals ◽  
Bulk Modulus ◽  
Critical Point ◽  
First Principles ◽  
Cohesive Energy ◽  
First Principles Calculations ◽  
Structure Parameter ◽  
Valence Transition ◽  
Pure Metals

First principles calculations were carried out to study the equilibrium properties of metals, including the electrons at bonding critical point; ebcp; cohesive energy; Ecoh; bulk modulus; B; and, atomic volume; V. 44 pure metals, including the s valence (alkali), p valence (groups III to V), and d valence (transition) metals were selected. In the present work, the electronic structure parameter ebcp has been considered to be a bridge connecting with the equilibrium properties of metals, and relationships between ebcp and equilibrium properties (V; Ecoh; and B) are established. It is easy to estimate the equilibrium properties (Ecoh; V, and B) of pure metals through proposed formulas. The relationships that were derived in the present work might provide a method to study the intrinsic mechanisms of the equilibrium properties of alloys and to develop new alloys.

A comparison of mechanical properties between Al and Al3Mg

2016 ◽  
Vol 30 (01) ◽  
pp. 1550243 ◽  
Author(s):  
Rong Yang ◽  
Bin Tang ◽  
Tao Gao
Keyword(s):  
Elastic Properties ◽  
Failure Modes ◽  
Md Simulations ◽  
First Principles Calculations ◽  
Stress Strain ◽  
Hardening Mechanisms ◽  
Experimental Values ◽  
The Individual ◽  
Theoretical Results ◽  
The Ideal

On the basis of first principles calculations, we have calculated the elastic properties, stress–strain relations, ideal tensile strengths, ideal shear strengths, and the ideal compressed strengths of Al and Al3Mg. The stress–strain relations of Al3Mg are strikingly similar to those of Al, indicating that the crystal structure appears to be more important than the identity of the individual atoms during uniaxial deformation. Al3Mg is found to have larger moduli and higher strengths than Al but less ductile than Al. So Al3Mg is expected to be a harder material, consistent with its exploitation in Al precipitate-hardening mechanisms. The calculated elastic properties, tensile strengths and shear strengths of Al are consistent with experimental values or previous theoretical results. We also use another method (molecular dynamics (MD) simulations) to recalculate elastic constants, ideal tensile and compressed strength of Al3Mg for checking and comparing. We find that the results obtained by the two methods agree well with each other. The failure modes under uniaxial [Formula: see text] tension are also explored for Al and Al3Mg. Our calculations confirm that Al fail by shear and predict that Al3Mg also fail by shear.

First Principles Study on Shear Deformation of TIN/BN/TIN Interface

2011 ◽  
Vol 335-336 ◽  
pp. 502-505 ◽  
Author(s):  
Wei Gao ◽  
Fei Xie ◽  
Ke Jun Jia
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Shear Deformation ◽  
Deformation Mechanism ◽  
First Principles ◽  
Calculation Method ◽  
First Principles Calculation ◽  
Strain Response ◽  
Stress Strain ◽  
Shear Process

To obtain a view of the shear deformation mechanism, ideal shear strength and hardness in superhard nanocomposites nc-TiN/a-BN films, we studied, using the first-principles calculation method, the shear stress-strain response of a theoretical interfacial system TiN/BN/TiN, which consists of two TiN slabs and one sandwiched BN monolayer. The shear process showed that decohesion happens at the Ti-N interplanar bonds next to the interface. The calculated results show that the TiN/BN/TiN interface has the hardness that can match the TiN/SiN/TiN syatem.

Theory of Point Defects and Interfaces

1996 ◽  
Vol 449 ◽  
Author(s):  
Chris G Van de Walle ◽  
Jörg Neugebauer
Keyword(s):  
Electronic Structure ◽  
Point Defects ◽  
First Principles ◽  
Current Understanding ◽  
Nitride Semiconductors ◽  
Yellow Luminescence ◽  
Materials Properties ◽  
Theoretical Results ◽  
Atomic And Electronic Structure

ABSTRACTFirst-principles theoretical results can predict and explain a variety of materials properties of the nitride semiconductors. For n-type GaN, we summarize the current understanding about incorporation of unintentional donor impurities, as opposed to nitrogen vacancies. For p-type GaN, we discuss the cause of the limited doping levels, and the role of hydrogen. We describe the role of gallium vacancies in the yellow luminescence, and the interaction between these vacancies and donor impurities. Finally, we discuss our first-principles investigations of the atomic and electronic structure of heterojunction interfaces between the III-nitrides, and provide values for natural band lineups.

scholarly journals Thermodynamics of thorium substitution in yttrium iron garnet: comparison of experimental and theoretical results

2014 ◽  
Vol 2 (40) ◽  
pp. 16945-16954 ◽  
Author(s):  
X. Guo ◽  
Zs. Rak ◽  
A. H. Tavakoli ◽  
U. Becker ◽  
R. C. Ewing ◽  
...  
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Yttrium Iron Garnet ◽  
Electronic Structure Calculations ◽  
Yttrium Iron ◽  
Bearing Material ◽  
Calorimetric Measurements ◽  
Iron Garnet ◽  
Structure Calculations ◽  
Theoretical Results

The thermodynamic stability of Th-doped yttrium iron garnet (Y3Fe5O12, YIG) as a possible actinide-bearing material has been investigated using calorimetric measurements and first-principles electronic-structure calculations.

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