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.

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.

First principles calculation of the elastic constants of intermetallic compounds: metastable Al3Li

1991 ◽  
Vol 6 (2) ◽  
pp. 324-329 ◽  
Author(s):  
X-Q. Guo ◽  
R. Podloucky ◽  
A.J. Freeman
Keyword(s):  
Young’S Modulus ◽  
Elastic Constants ◽  
First Principles ◽  
Local Density ◽  
Young's Modulus ◽  
Poisson Ratio ◽  
First Principles Calculation ◽  
Full Potential ◽  
A Value ◽  
Experimental Values

We report first principles local density calculations for the metastable Al3Li intermetallic compound with cubic L12 crystal structure using the full-potential linearized augmented plane wave method. From the second derivative of the total energy as a function of volume, and generated tetragonal and trigonal lattice distortions, the elastic constants C11, C12, and C44 were derived yielding C11 = 158 GPa, C12 = 29.4 GPa, and C44 = 57.7 GPa. Because of the very high Young's modulus (E = 141 GPa) compared, for example, to pure Al (E = 66 GPa), it is suggested that Al3Li plays an important role in strengthening the Al–Li alloys. The calculated Young's modulus appears in good agreement with experimental estimates when the experimental values are extrapolated to 0 K. Although the Young's modulus of Al3Li is increased in comparison to Al, the calculated bulk modulus is decreased to a value of 72 GPa as compared to pure Al (82 GPa), in agreement with experiment. As a result, the Poisson ratio is reduced to ŝ = 0.173 as compared to the value 1/3 for an isotropic medium. Because of this and the high Young's modulus, the calculated Debye temperature ΘD at 0 K amounts to 672 K, which is substantially larger than ΘD for Al, which is about 400 K.

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.

Dynamic Stability of Ni FCC Crystal under Isotropic Tension

2013 ◽  
Vol 592-593 ◽  
pp. 47-50
Author(s):  
Petr Řehák ◽  
Miroslav Černý
Keyword(s):  
Dynamic Stability ◽  
Wave Vector ◽  
First Principles ◽  
Lattice Dynamics ◽  
Harmonic Approximation ◽  
Tensile Loading ◽  
The Other ◽  
Other Hand ◽  
Critical Strains

Lattice dynamics and stability of fcc crystal of Ni under isotropic (hydrostatic) tensile loading are studied from first principles using supercell method and a harmonic approximation. According to the results, strength of the crystal is determined by occurrence of an instability related to soft phonons with finite wave vector. On the other hand, the critical strains and stresses associated with such instabilities are only slightly lower than those related to the volumetric instability.

A dynamical method for the determination of Young's modulus by stretching

1928 ◽  
Vol 24 (2) ◽  
pp. 276-279
Author(s):  
C. F. Sharman
Keyword(s):  
Young’S Modulus ◽  
Elastic Constants ◽  
Young's Modulus ◽  
The Other ◽  
Static Deformation ◽  
Elastic Forces ◽  
Dynamical Method ◽  
Period Of Oscillation

There are two general methods of measuring the elastic constants of bodies; one involves a study of the static deformation produced by the appropriate kind of stress, and the other a measurement of the period of oscillation of a system of known inertia under the elastic forces.

scholarly journals The Elastic Constants of the Single Crystal of the Mg-Zn-Zr-REM Alloy from the Data of the Elastic Anisotropy and the Texture of the Polycrystalline Sheet

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
S. V. San’kova ◽  
N. M. Shkatulyak ◽  
V. V. Usov ◽  
N. A. Volchok
Keyword(s):  
Single Crystals ◽  
Young’S Modulus ◽  
Elastic Constants ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
Rare Earth Metals ◽  
Alloy Sheet ◽  
Pole Figures ◽  
Integral Characteristics ◽  
Experimental Values

The measuring of the constants of single-crystals requires the availability of crystals of relatively big size. In this paper the elastic constants of the single crystals of magnesium alloy with zinc, zirconium, and rare earth metals (REM) were determined by means of the experimental anisotropy of Young’s modulus and integral characteristics of texture (ICT), which were found from pole figures. Using these constants the anisotropy of Young’s modulus of alloy sheet ZE10 was calculated. Deviation of calculated values from experimental values did not exceed 2%.

Mechanical degradation of graphene by epoxidation: insights from first-principles calculations

2015 ◽  
Vol 17 (29) ◽  
pp. 19484-19490 ◽  
Author(s):  
Qing Peng ◽  
Liang Han ◽  
Jie Lian ◽  
Xiaodong Wen ◽  
Sheng Liu ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
First Principles ◽  
Young's Modulus ◽  
Mechanical Degradation ◽  
First Principles Calculations

The in-plane Young's modulus decreases with the degree of epoxidation.

scholarly journals Benefits of Nonthermal Atmospheric Plasma Treatment on Dentin Adhesion

2018 ◽  
Vol 43 (6) ◽  
pp. E288-E299 ◽  
Author(s):  
AP Ayres ◽  
PH Freitas ◽  
J De Munck ◽  
A Vananroye ◽  
C Clasen ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Water Storage ◽  
Contact Angles ◽  
The Other ◽  
Atmospheric Plasma ◽  
Hybrid Layer ◽  
Water Contact ◽  
Dentin Surface

SUMMARY Objectives: This study aimed to evaluate the influence of two nonthermal atmospheric plasma (NTAP) application times and two storage times on the microtensile bond strength (μTBS) to dentin. The influence of NTAP on the mechanical properties of the dentin-resin interface was studied by analyzing nanohardness (NH) and Young's modulus (YM). Water contact angles of pretreated dentin and hydroxyapatite blocks were also measured to assess possible alterations in the surface hydrophilicity upon NTAP. Methods and Materials: Forty-eight human molars were used in a split-tooth design (n=8). Midcoronal exposed dentin was flattened by a 600-grit SiC paper. One-half of each dentin surface received phosphoric acid conditioning, while the other half was covered with a metallic barrier and remained unetched. Afterward, NTAP was applied on the entire dentin surface (etched or not) for 10 or 30 seconds. The control groups did not receive NTAP treatment. Scotchbond Universal (SBU; 3M ESPE) and a resin-based composite were applied to dentin following the manufacturer's instructions. After 24 hours of water storage at 37°C, the specimens were sectioned perpendicular to the interface to obtain approximately six specimens or bonded beams (approximately 0.9 mm2 in cross-sectional area) representing the etch-and-rinse (ER) approach and another six specimens representing the self-etch (SE) approach. Half of the μTBS specimens were immediately loaded until failure, while the other half were first stored in deionized water for two years. Three other bonded teeth were selected from each group (n=3) for NH and YM evaluation. Water contact-angle analysis was conducted using a CAM200 (KSV Nima) goniometer. Droplet images of dentin and hydroxyapatite surfaces with or without 10 or 30 seconds of plasma treatment were captured at different water-deposition times (5 to 55 seconds). Results: Two-way analysis of variance revealed significant differences in μTBS of SBU to dentin after two years of water storage in the SE approach, without differences among treatments. After two years of water aging, the ER control and ER NTAP 10-second groups showed lower μTBS means compared with the ER NTAP 30-second treated group. Nonthermal atmospheric plasma resulted in higher NH and YM for the hybrid layer. The influence of plasma treatment in hydrophilicity was more evident in the hydroxyapatite samples. Dentin hydrophilicity increased slightly after 10 seconds of NTAP, but the difference was higher when the plasma was used for 30 seconds. Conclusions: Dentin NTAP treatment for 30 seconds contributed to higher μTBS after two years of water storage in the ER approach, while no difference was observed among treatments in the SE evaluation. This result might be correlated to the increase in nanohardness and Young's modulus of the hybrid layer and to better adhesive infiltration, since dentin hydrophilicity was also improved. Although some effects were observed using NTAP for 10 seconds, the results suggest that 30 seconds is the most indicated treatment time.

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