scholarly journals First-principles investigations on the anisotropic elasticity and thermodynamic properties of U3Si2–Al

RSC Advances ◽  
2020 ◽  
Vol 10 (58) ◽  
pp. 35049-35056
Author(s):  
Xinyu Chen ◽  
Yanqing Qin ◽  
Diwei Shi ◽  
Yaolin Guo ◽  
Moran Bu ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Young’S Modulus ◽  
First Principles ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
Three Dimensional ◽  
Anisotropic Elasticity

Three-dimensional Young's modulus diagrams of different structures are used to judge the degree of elastic anisotropy.

First-Principles Study of Structural, Mechanical, and Thermodynamic Properties of Refractory Metals (Rh, Ir, W, Ta, Nb, Mo, Re, and Os)

2020 ◽  
Vol 993 ◽  
pp. 1017-1030
Author(s):  
Ying Jie Sun ◽  
Kai Xiong ◽  
Zong Bo Li ◽  
Shun Meng Zhang ◽  
Yong Mao
Keyword(s):  
Thermodynamic Properties ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Young’S Modulus ◽  
First Principles ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
Refractory Metals ◽  
Body Centered Cubic ◽  
Cubic Metals

The structural, mechanical, and thermodynamic properties of refractory metals Rh, Ir, W, Ta, Nb, Mo, Re, and Os have been systematically investigated by first-principles calculations based on density functional theory. Comparative studies reveal that Young's modulus (E = 636.42 GPa), shear modulus (G = 256.81 GPa), bulk modulus (B = 406.55 GPa), and microhardness (H = 44.69 GPa) of hexagonal Os are the highest, which reveals Os has the best overall mechanical properties. The body-centered cubic Nb has the smallest Young's modulus (E = 94.76 GPa), shear modulus (G = 33.62 GPa), bulk modulus (B = 174.50 GPa), and hardness (H = 2.04 GPa). Based on the ratio of bulk to shear modulus, it is judged that Rh, Ir, and Os are brittle materials (B/G < 1.75), and Nb, Ta, Mo, W, and Re exhibit ductile (B/G > 1.75). The elastic anisotropy has also been discussed by plotting both the 3D contours and the 2D planar projections of Young's modulus. For the face-centered cubic metals Rh and Ir and hexagonal close-packed metals Re and Os, the 3D contours of the Young's modulus are very similar, whereas body-centered cubic metals Ta, W, Nb, and Mo exhibit significant difference in elastic anisotropy. The thermodynamic calculations show that Debye temperature and minimum thermal conductivity decreases along Rh, Os, Mo, Ir, Re, W, Ta, Nb sequence. Furthermore, the results can be used as a general guidance for the design and development of high temperature refractory alloy system.

First-Principles Calculations of Thermoelectric PbSe2 Compound to Predict its Elastic Properties

2019 ◽  
Vol 956 ◽  
pp. 46-54
Author(s):  
Jia Fu ◽  
Tian Hou ◽  
Jing Rui Chen
Keyword(s):  
Young’S Modulus ◽  
Elastic Properties ◽  
First Principles ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
Poisson Ratio ◽  
Structural Parameters ◽  
Homogenization Method ◽  
Parameter Method ◽  
G Ratio

The influencing effect of pressure on structural stability and elastic properties of PbSe2 compound is mainly investigated by first-principles method and homogenization method of the Y parameter. The optimized structural parameters at zero pressure are a=b=6.446Å, c=7.887Å (GGA method) and a=b=6.316Å, c=7.651Å (LDA method), which has good agreement with the experimental and theoretical values. Our calculated lattice parameters and Se-Se bond length are in excellent agreement with experimental data. PbSe2 compound is energetically stable with a good alloying ability. The elastic constants are calculated, and then the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and anisotropy factor are determined. Besides, Y parameter method is used to investigate changes of the Poisson ratio, Young’s and shear moduli of PbSe2 within different normal orientation crystal planes. Results show that: 1) Young’s modulus is about 48.37 GPa from GGA and 58.87 GPa from LDA by Reuss-Voigt-Hill estimation, which is averaged about 53.62 GPa; 2) The PbSe2 compound is ductile according to B/G ratio. The universal anisotropic index AU shows that PbSe2 exhibits a fairly high elastic anisotropy.

scholarly journals Research on Mechanical Properties of High-Pressure Anhydrite Based on First Principles

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 240
Author(s):  
Xianren Zeng ◽  
Shihui You ◽  
Linmei Li ◽  
Zhangli Lai ◽  
Guangyan Hu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Bulk Modulus ◽  
Young’S Modulus ◽  
First Principles ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Three Dimensional ◽  
Poisson's Ratio ◽  
Physical Parameters ◽  
Three Dimensional Model

This article focuses on the elucidation of a three-dimensional model of the structure of anhydrite crystal (CaSO4). The structure parameters of anhydrite crystal were obtained by means of first principles after structure optimization at 0~120 MPa. In comparison with previous experimental and theoretical calculation values, the results we obtained are strikingly similar to the previous data. The elastic constants and physical parameters of anhydrite crystal were also studied by the first-principles method. Based on this, we further studied the Young’s modulus and Poisson’s ratio of anhydrite crystal, the anisotropy factor, the speed of sound, the minimum thermal conductivity and the hardness of the material. It was shown that the bulk modulus and Poisson’s ratio of anhydrite crystal rose slowly with increasing pressure. The anisotropy characteristics of the Young’s modulus and shear modulus of anhydrite crystal were consistent under various pressure levels, while the difference in the anisotropy characteristics of the bulk modulus appeared. The acoustic velocities of anhydrite crystal tended to be stable with increasing pressure. The minimum thermal conductivity remained relatively unchanged with increasing pressure. However, the material hardness declined gradually with increasing pressure.

Topology of charge density and elastic anisotropy of Ti3SiC2 polymorphs

2005 ◽  
Vol 20 (5) ◽  
pp. 1180-1185 ◽  
Author(s):  
R. Yu ◽  
X.F. Zhang ◽  
L.L. He ◽  
H.Q. Ye
Keyword(s):  
Charge Density ◽  
Young’S Modulus ◽  
First Principles ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
The Other ◽  
Full Potential ◽  
Density Topology ◽  
Other Hand ◽  
First Principles Method

Using an all-electron, full potential first-principles method, we have investigated the topology of charge density and elastic anisotropy of Ti3SiC2 polymorphs comparatively. By analyzing the charge density topology, it was found that the Ti–Si bonds are weaker in β than in α, resulting in a destabilizing effect and lower Young’s modulus in directions between a and c axes for β. On the other hand, the Si–C bonds (absent in α) are formed in β in the c direction. The formation of the Si–C bonds not only mitigates the destabilizing effect of the weaker Ti–Si bonds, but also results in larger Young’s modulus in the c direction. In contrast to the high elastic anisotrophy, the elastic anisotropy of Ti3SiC2 is very low.

Elastic and Thermal Properties of Silicon Compounds from First-Principles Calculations

2016 ◽  
Vol 71 (7) ◽  
pp. 657-664 ◽  
Author(s):  
Haijun Hou ◽  
H.J. Zhu ◽  
W.H. Cheng ◽  
L.H. Xie
Keyword(s):  
Young’S Modulus ◽  
Elastic Properties ◽  
First Principles ◽  
Young's Modulus ◽  
Three Dimensional ◽  
Formation Enthalpy ◽  
Debye Model ◽  
Silicon Compounds ◽  
Calculated Equilibrium ◽  
Good Agreement

AbstractThe structural and elastic properties of V-Si (V3Si, VSi2, V5Si3, and V6Si5) compounds are studied by using first-principles method. The calculated equilibrium lattice parameters and formation enthalpy are in good agreement with the available experimental data and other theoretical results. The calculated results indicate that the V-Si compounds are mechanically stable. Elastic properties including bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio are also obtained. The elastic anisotropies of V-Si compounds are investigated via the three-dimensional (3D) figures of directional dependences of reciprocals of Young’s modulus. Finally, based on the quasi-harmonic Debye model, the internal energy, Helmholtz free energy, entropy, heat capacity, thermal expansion coefficient, Grüneisen parameter, and Debye temperature of V-Si compounds have been calculated.

scholarly journals Anisotropies in Elasticity, Sound Velocity, and Minimum Thermal Conductivity of Low Borides VxBy Compounds

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 577
Author(s):  
Jing Yu ◽  
Yongmei Zhang ◽  
Yuhong Zhao ◽  
Yue Ma
Keyword(s):  
Thermal Conductivity ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Sound Velocity ◽  
Young’S Modulus ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
Three Dimensional ◽  
Young’S Moduli ◽  
Crystallographic Planes

Anisotropies in the elasticity, sound velocity, and minimum thermal conductivity of low borides VB, V5B6, V3B4, and V2B3 are discussed using the first-principles calculations. The various elastic anisotropic indexes (AU, Acomp, and Ashear), three-dimensional (3D) surface contours, and their planar projections among different crystallographic planes of bulk modulus, shear modulus, and Young’s modulus are used to characterize elastic anisotropy. The bulk, shear, and Young’s moduli all show relatively strong degrees of anisotropy. With increased B content, the degree of anisotropy of the bulk modulus increases while those of the shear modulus and Young’s modulus decrease. The anisotropies of the sound velocity in the different planes show obvious differences. Meanwhile, the minimum thermal conductivity shows little dependence on crystallographic direction.

scholarly journals First principles computation of composition dependent elastic constants of omega in titanium alloys: implications on mechanical behavior

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Salloom ◽  
S. A. Mantri ◽  
R. Banerjee ◽  
S. G. Srinivasan
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
First Principles ◽  
Young's Modulus ◽  
Group Vi ◽  
Group V ◽  
Β Phase ◽  
Ti Alloys ◽  
Ω Phase ◽  
Stabilizer Concentration

AbstractFor decades the poor mechanical properties of Ti alloys were attributed to the intrinsic brittleness of the hexagonal ω-phase that has fewer than 5-independent slip systems. We contradict this conventional wisdom by coupling first-principles and cluster expansion calculations with experiments. We show that the elastic properties of the ω-phase can be systematically varied as a function of its composition to enhance both the ductility and strength of the Ti-alloy. Studies with five prototypical β-stabilizer solutes (Nb, Ta, V, Mo, and W) show that increasing β-stabilizer concentration destabilizes the ω-phase, in agreement with experiments. The Young’s modulus of ω-phase also decreased at larger concentration of β-stabilizers. Within the region of ω-phase stability, addition of Nb, Ta, and V (Group-V elements) decreased Young’s modulus more steeply compared to Mo and W (Group-VI elements) additions. The higher values of Young’s modulus of Ti–W and Ti–Mo binaries is related to the stronger stabilization of ω-phase due to the higher number of valence electrons. Density of states (DOS) calculations also revealed a stronger covalent bonding in the ω-phase compared to a metallic bonding in β-phase, and indicate that alloying is a promising route to enhance the ω-phase’s ductility. Overall, the mechanical properties of ω-phase predicted by our calculations agree well with the available experiments. Importantly, our study reveals that ω precipitates are not intrinsically embrittling and detrimental, and that we can create Ti-alloys with both good ductility and strength by tailoring ω precipitates' composition instead of completely eliminating them.

FEM Stress Analysis and Strength of Scarf Adhesive Joints of Similar Adherend Subjected to Impact Tensile Loadings

2007 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Yuya Hirayama ◽  
He Dan
Keyword(s):  
Young’S Modulus ◽  
Principal Stress ◽  
Stress Wave ◽  
Young's Modulus ◽  
Three Dimensional ◽  
Maximum Principal Stress ◽  
Adhesive Joints ◽  
Stress Wave Propagation ◽  
Adhesive Thickness ◽  
Three Dimensional Finite Element

The stress wave propagation and stress distribution in scarf adhesive joints have been analyzed using three-dimensional finite element method (FEM). The FEM code employed was LS-DYNA. An impact tensile loading was applied to the joint by dropping a weight. The effect of the scarf angle, Young’s modulus of the adhesive and adhesive thickness on the stress wave propagations and stress distributions at the interfaces have been examined. As the results, it was found that the point where the maximum principal stress becomes maximum changes between 52 degree and 60 degree under impact tensile loadings. The maximum value of the maximum principal stress increases as scarf angle decreases, Young’s modulus of the adhesive increases and adhesive thickness increases. In addition, Experiments to measure the strains and joint strengths were compared with the calculated results. The calculated results were in fairly good agreements with the experimental results.

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