scholarly journals First principles calculation of single‐crystal elastic constants of titanium tetraboride (Ti 3 B 4 ) and experimental validation

2018 ◽  
Vol 101 (9) ◽  
pp. 4308-4320 ◽  
Author(s):  
Somnaang Rou ◽  
K. S. Ravi Chandran
Keyword(s):  
Single Crystal ◽  
Elastic Constants ◽  
First Principles ◽  
Experimental Validation ◽  
First Principles Calculation

Effect of Alloying Elements V, Cr and Ni on the Electronic Structure and Mechanical Properties of FeAl from First-Principles Calculation

2014 ◽  
Vol 887-888 ◽  
pp. 378-383 ◽  
Author(s):  
Yu Chen ◽  
Zheng Jun Yao ◽  
Ping Ze Zhang ◽  
Dong Bo Wei ◽  
Xi Xi Luo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electronic Structure ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
Valence Bond ◽  
Ternary Alloys ◽  
First Principles Calculation ◽  
Structure Stability ◽  
Alloying Element

The structure stability, mechanical properties and electronic structures of B2 phase FeAl intermetallic compounds and FeAl ternary alloys containing V, Cr or Ni were investigated using first-principles density functional theory calculations. Several models are established. The total energies, cohesive energies, lattice constants, elastic constants, density of states, and the charge densities of Fe8Al8 and Fe8XAl7 ( X=V, Cr, Ni ) are calculated. The stable crystal structures of alloy systems are determined due to the cohesive energy results. The calculated lattice contants of Fe-Al-X ( X= V, Cr, Ni) were found to be related to the atomic radii of the alloy elements. The calculation and analysis of the elastic constants showed that ductility of FeAl alloys was improved by the addition of V, Cr or Ni, the improvement was the highest when Cr was used. The order of the ductility was as follows: Fe8CrAl7 > Fe8NiAl7 > Fe8VAl7 > Fe8Al8. The results of electronic structure analysis showed that FeAl were brittle, mainly due to the orbital hybridization of the s, p and d state electron of Fe and the s and p state electrons of Al, showing typical characteristics of a valence bond. Micro-mechanism for improving ductility of FeAl is that d orbital electron of alloying element is maily involved in hybridization of FeAl, alloying element V, Cr and Ni decrease the directional property in bonding of FeAl.

First Principles Calculation of Elastic Constants of Monoclinic HfO2Thin Film

2013 ◽  
Vol 33 (1) ◽  
pp. 0131001
Author(s):  
蔺玲 Lin Ling ◽  
邵淑英 Shao Shuying ◽  
李静平 Li Jingping
Keyword(s):  
Elastic Constants ◽  
First Principles ◽  
First Principles Calculation

Site Preference of Refractory Elements in Ni-Based Single-Crystal Superalloys Alloying with Ru: From First Principles

2012 ◽  
Vol 554-556 ◽  
pp. 3-12
Author(s):  
Jian Jun Cui ◽  
Fei Sun ◽  
Jian Xin Zhang
Keyword(s):  
Binding Energy ◽  
Single Crystal ◽  
First Principles ◽  
First Principles Calculation ◽  
Partial Density ◽  
Site Preference ◽  
Strengthening Effect ◽  
Mulliken Population ◽  
Calculation Results ◽  
Partitioning Behavior

A first principles calculation method was used to investigate the site preference of Ruthenium (Ru) at the γ/γ′ interface in Ni-based single-crystal superalloys. The calculation results show that the addition of Ru can decrease the total energy and the binding energy of γ/γ′ interface, which may result in an improved microstructure stability of Ni-based single-crystal superalloys. Moreover, by calculation, it is also found that Ru can stabilize both γ and γ′ phases and have a preference for Ni site at the coherent γ/γ′ interface. When Ru substitutes the central Ni at the γ/γ′ interface, a reverse partitioning of W, Re and Cr occurs; while the partitioning behavior of Mo is not affected. The influence of Ru on the partitioning behavior of W, Re and Cr in γ′-Ni3Al was studied by Dmol3 calculation as well. The calculation results show that W, Re and Cr have a preference for Ni site in γ′- Ni3Al with Ru alloying. When Ru substitutes the central Ni atom, the site preference of W, Re and Cr varies accordingly. Furthermore, electronic structure analysis of γ/γ′ interface and γ′-Ni3Al in terms of Mulliken population and partial density of states (PDOS) was performed to understand the alloying mechanism of Ru in Ni-based single-crystal superalloys. The results show that the strengthening effect of Ru alloying is mainly due to the reduction in binding energy of Ru as well as a p-orbital hybridization between Ru and the host atoms.

Novel elastic evolution of carbide Mo2Ga2C under pressure: Ab initio theoretical investigation

2019 ◽  
Vol 33 (30) ◽  
pp. 1950358
Author(s):  
Rui Wu ◽  
Hai-Chen Wang ◽  
Yan Yang ◽  
Li Ma ◽  
Shan Jiang ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Elastic Constants ◽  
Pressure Dependence ◽  
First Principles ◽  
Phonon Mode ◽  
First Principles Calculation ◽  
Max Phases ◽  
Transverse Acoustic ◽  
Phonon Structure

The pressure dependence of elastic properties of Mo2Ga2C is studied via first-principles calculation. The present investigation shows that differing from other MAX phases, in Mo2Ga2C the [Formula: see text] is larger than [Formula: see text], because of the strong Ga–Ga interlayer bonds along [Formula: see text]-axis. Moreover, under pressure, the [Formula: see text] increases more rapidly, originating from the faster strengthening of Ga–Ga bonds. Interestingly, elastic constants [Formula: see text] soften under high pressure (more than 20 GPa). Especially, the calculated phonon structure demonstrates that transverse acoustic (TA) phonon mode also softens under pressure, implying possible phase transition. The reduction of [Formula: see text] and softening of phonon mode are attributed to significantly weakened Mo–Mo interaction in contrast to the strengthening of Ga–Ga bonds under high pressure. Our present results further indicate that Mo2Ga2C is more ductile under pressure.

scholarly journals First-Principles Calculations to Investigate the Third-Order Elastic Constants and Mechanical Properties of Mg, Be, Ti, Zn, Zr, and Cd

2021 ◽  
Vol 2021 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaoqing Yang ◽  
Zhenya Meng ◽  
Hailin Cao
Keyword(s):  
High Pressure ◽  
Elastic Constants ◽  
First Principles ◽  
Deformation Gradient ◽  
Elastic Strain Energy ◽  
Pressure Effects ◽  
First Principles Calculation ◽  
Third Order ◽  
The Third ◽  
Third Order Elastic Constants

We present theoretical studies for the third-order elastic constants of Mg, Be, Ti, Zn, Zr, and Cd with a hexagonal-close-packed (HCP) structure. The method of homogeneous deformation combined with first-principles total-energy calculations is employed. The deformation gradient F i j is applied to the crystal lattice vectors r i , and the elastic strain energy can be obtained from the first-principles calculation. The second- and third-order elastic constants are extracted by a polynomial fit to the calculated energy-strain results. In order to assure the accuracy of our method, we calculated the complete set of the equilibrium lattice parameters and second-order elastic constants for Mg, Be, Ti, Zn, Zr, and Cd, and our results provide better agreement with the previous calculated and experimental values. Besides, we have calculated the pressure derivatives of SOECs related to third-order elastic constants, and high-pressure effects on elastic anisotropy, ductile-to-brittle criterion, and Vickers hardness are also investigated. The results show that the hardness model H v = 1.877 k 2 G 0.585 is more appropriate than H v = 2 k 2 G 0.585 − 3 for HCP metals under high pressure.

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