Elastic Constants of A Laves Phase Compound: C15 NbCr2

1996 ◽  
Vol 460 ◽  
Author(s):  
Alim Ormeci ◽  
F. Chu ◽  
John M. Wills ◽  
S. P. Chen ◽  
R. C. Albers ◽  
...  
Keyword(s):  
Single Crystal ◽  
Elastic Constants ◽  
Energy Method ◽  
First Principles ◽  
Elastic Moduli ◽  
Full Potential ◽  
Self Consistent ◽  
Phase Compound ◽  
Direction Dependence ◽  
Experimental Values

ABSTRACTThe single-crystal elastic constants of C15 NbCr2 have been computed by using a first-principles, self-consistent, full-potential total energy method. From these single-crystal elastic constants the isotropie elastic moduli are calculated using the Voigt and Reuss averages. The calculated values are in fair agreement with the experimental values. The implications of the results are discussed with regards to Poisson's ratio and the direction dependence of Young's modulus.

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.

FIRST-PRINCIPLES HIGH-PRESSURE ELASTIC AND THERMODYNAMIC PROPERTIES OF TANTALUM

2011 ◽  
Vol 25 (10) ◽  
pp. 1393-1407 ◽  
Author(s):  
JING-HE WU ◽  
XIAN-LIN ZHAO ◽  
YOU-LIN SONG ◽  
GUO-DONG WU
Keyword(s):  
Thermodynamic Properties ◽  
Elastic Constants ◽  
First Principles ◽  
Equations Of State ◽  
Debye Model ◽  
Thermal Expansivity ◽  
Orbital Method ◽  
Full Potential ◽  
Body Centered Cubic ◽  
Theoretical Results

The all-electron full-potential linearized muffin-tin orbital method, by means of quasi-harmonic Debye model, is applied to investigate the elastic constant and thermodynamic properties of body-centered-cubic tantalum (bcc Ta). The calculated elastic constants of bcc Ta at 0 K is consistent with the previous experimental and theoretical results. Our calculations give the correct trends for the pressure dependence of elastic constants. By using the convenient quasi-harmonic Debye model, we refined the thermal equations of state. The thermal expansivity and some other thermal properties agree well with the previous experimental and theoretical results.

First-Principles Total Energy Study of NbCr2 + V Laves Phase Ternary System

1998 ◽  
Vol 552 ◽  
Author(s):  
Alim Ormeci ◽  
S. P. Chen ◽  
John M. Wills ◽  
R. C. Albers
Keyword(s):  
Ternary System ◽  
Total Energy ◽  
Density Of States ◽  
First Principles ◽  
Laves Phase ◽  
Full Potential ◽  
Self Consistent ◽  
Substitutional Defects ◽  
Cohesive Energies ◽  
Formation Energies

ABSTRACTThe C15 NbCr2 + V Laves phase ternary system is studied by using a first-principles, self-consistent, full-potential total energy method. Equilibrium lattice parameters, cohesive energies, density of states and formation energies of substitutional defects are calculated. Results of all these calculations show that in the C15 NbCr2 + V compounds, V atoms substitute Cr atoms only.

Electric Field Gradient Calculations of Various Borides

1996 ◽  
Vol 51 (5-6) ◽  
pp. 527-533 ◽  
Author(s):  
K. Schwarz ◽  
H. Ripplinger ◽  
P. Blaha
Keyword(s):  
Electric Field ◽  
First Principles ◽  
Density Functional ◽  
The Self ◽  
Full Potential ◽  
Electric Field Gradients ◽  
Charge Density Distribution ◽  
Functional Theory ◽  
Field Gradients ◽  
Self Consistent

Abstract A first-principles method for the computation of electric field gradients (EFG) is illustrated for various borides. It is based on energy band calculations using the full-potential linearized aug-mented plane wave (LAPW) method within density functional theory. From the self-consistent charge density distribution the EFG is obtained without further approximations by numerically solving Poisson's equation. The dependence of the EFG on structure, chemical composition or substitution is demonstrated for the diborides MB2 (with M = Ti, V, Cr, Zr, Nb, Mo, and Ta), the hexaborides (CaB6, SrB6 and BaB6) and boron carbide which is closely related to α-boron.

First-Principles Investigation of Structural Stability, Mechanical, Anisotropic, and Thermodynamic Properties of CeT2Al20 Intermetallics

2018 ◽  
Vol 73 (12) ◽  
pp. 1157-1167 ◽  
Author(s):  
He Ma ◽  
Xiaoyou Li ◽  
Wei Jiang ◽  
Xudong Zhang
Keyword(s):  
High Temperature ◽  
Thermodynamic Properties ◽  
Thermodynamic Parameters ◽  
Structural Stability ◽  
Elastic Constants ◽  
First Principles ◽  
Elastic Moduli ◽  
Formation Enthalpy ◽  
First Principles Calculations ◽  
Acoustic Velocities

AbstractFirst-principles calculations were carried out to explore the structural stability, elastic moduli, ductile or brittle behaviour, anisotropy, dynamical stability, and thermodynamic properties of pure Al and CeT2Al20 (T = Ti, V, Cr, Nb, and Ta) intermetallics. The calculated formation enthalpy and phonon frequencies confirm that these intermetallics satisfy the conditions for structural stability. The elastic constants Cij, elastic moduli B, G, and E, and the hardness Hv indicate these intermetallics have higher hardness and the better resistance against deformation than pure Al. The values of Poisson’s ratio (v) and B/G indicate that CeT2Al20 intermetallics are all brittle materials. The anisotropic constants and acoustic velocities confirm that CeT2Al20 intermetallics are all anisotropic, but CeV2Al20, CeNb2Al20, and CeTa2Al20 are nearly isotropic. Importantly, the calculated thermodynamic parameters show that CeT2Al20 intermetallics exhibit better thermodynamic properties than pure Al at high temperature.

First-Principles Study of the Mechanical Properties of Mg-Based Alloys with FCC and Hexagonal Structure

2009 ◽  
Vol 610-613 ◽  
pp. 848-852
Author(s):  
Na Wang ◽  
Wei Yang Yu ◽  
Wei Bing Zhang ◽  
Bi Yu Tang ◽  
Xiao Qin Zeng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
Hexagonal Structure ◽  
Experimental Investigations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Fundamental Mechanism

More and more research has been focused on the improvement of the mechanical properties and the optimal design of the new excellent Mg-based alloys. In spite of many experimental investigations, the theoretical studies of the mechanical properties are very scarce. First-principle calculations of the elastic constants and mechanical properties of typical Mg-based alloys become necessary to understand the fundamental mechanism governing the observed mechanical properties. In this paper, the single-crystal elastic constants Cijs of the typical fcc and hexagonal structured Mg-based alloys (Mg3Zn3Y2 and CaMg2) were calculated, using density functional theory within the generalized gradient approximation. Then the bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio ν and anisotropy value A were derived from single-crystal elastic constants. The mechanical properties such as the ductility and stiffiness of the alloys are analyzed and discussed in comparison with experimental observations.

High-Pressure Third-Order Elastic Constants of MgO Single Crystal: First-Principles Investigation

2019 ◽  
Vol 74 (5) ◽  
pp. 447-456
Author(s):  
Jianbing Gu ◽  
Chenju Wang ◽  
Bin Sun ◽  
Weiwei Zhang ◽  
Dandan Liu
Keyword(s):  
High Pressure ◽  
Single Crystal ◽  
Total Energy ◽  
Elastic Constants ◽  
First Principles ◽  
Predictive Ability ◽  
Theoretical Method ◽  
Third Order ◽  
Third Order Elastic Constants ◽  
First Time

AbstractHigh-pressure third-order elastic constants of materials have rarely been investigated experimentally and theoretically to date, so the predictive ability of the method of the volume-conserving, homogeneous deformations based on the first-principles total-energy calculations is tested for the first time in this work. Using this approach, the high-pressure third-order elastic constants ${C_{111}}-3{C_{112}}+2{C_{123}}$, ${C_{111}}/2+3{C_{112}}+{C_{123}}$, ${C_{144}}-{C_{155}}$, and C456 of the MgO single crystal are obtained successfully. Meanwhile, the reliability of this method is also verified by comparing the calculated structural properties and high-pressure second-order elastic constants of the MgO single crystal with the available experimental results and other theoretical predications. Results not only indicate the accuracy of our calculations but also reveal the feasibility of the present theoretical method. It is hoped that the present theoretical method and predictions on the high-pressure third-order elastic constants of the MgO single crystal would serve as a valuable guidance or reference for further related investigations.

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