ELECTRONIC AND ELASTIC PROPERTIES OF MgAl2O4 SPINEL AT HIGH ISOSTATIC PRESSURE: FIRST PRINCIPLE STUDY

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1695-1700 ◽  
Author(s):  
MEILING LI ◽  
FENGJIU SUN ◽  
PING ZHANG
Keyword(s):  
Bulk Modulus ◽  
Elastic Constants ◽  
Nearest Neighbor ◽  
Structural Instability ◽  
High Symmetry ◽  
First Principle ◽  
Lattice Constants ◽  
Bond Lengths ◽  
Energy Gaps ◽  
Internal Parameters

The calculations of mechanic and electronic properties for MgAl 2 O 4 spinel under pressure are presented by first principle. The lattice constants and internal parameters are in good agreement with the available experimental results. The calculations for bulk modulus, elastic constants, energy gaps, bond lengths for the nearest neighbor cation- O anion and their pressure dependence show an increase of bulk modulus, elastic constants, energy gaps in high symmetry and a decrease of cation- O anion bond lengths. A transition from indirect gap material to direct one is found due to applying pressure. Up to 70GPa, there is no sign of structural instability.

First Principle Study of Ti50Al50 Alloys

2018 ◽  
Vol 770 ◽  
pp. 224-229
Author(s):  
Rosinah Modiba ◽  
Hasani Chauke ◽  
Phuti Ngoepe
Keyword(s):  
Experimental Data ◽  
High Temperatures ◽  
Elastic Constants ◽  
Martensitic Phase ◽  
First Principle ◽  
Lattice Constants ◽  
B2 Phase ◽  
Experimental Values ◽  
Good Agreement

The study on the Ti-based materials and its application has been the interest of many research industries. These alloys are known to have an ordered B2 phase at high temperatures and transform to a stable low B19 martensitic phase. First principle approach has been used to study L10, B32, B2 and B19 Ti50Al50alloys and the results compared well with the available experimental data. The equilibrium lattice constants are in good agreement with the experimental values (within 3% agreement). Furthermore, the elastic constants of these alloys are calculated, and revealed stability for L10and B19 structures, while B2 and B32 gave C′<0 (condition of instability).

FIRST PRINCIPLES STUDY OF THE STRUCTURAL, ELASTIC AND ELECTRONIC PROPERTIES OF Ti2InC and Ti2InN

2011 ◽  
Vol 25 (10) ◽  
pp. 747-761 ◽  
Author(s):  
N. BENAYAD ◽  
D. RACHED ◽  
R. KHENATA ◽  
F. LITIMEIN ◽  
ALI H. RESHAK ◽  
...  
Keyword(s):  
Bulk Modulus ◽  
Electronic Properties ◽  
First Principles ◽  
Local Density ◽  
Full Potential ◽  
Pressure Derivative ◽  
Lattice Constants ◽  
Internal Parameters ◽  
Correlation Potential ◽  
Lmto Method

The structural, elastic and electronic properties of Ti 2 InC and Ti 2 InN compounds have been calculated using the full-potential linear muffin-tin orbital (FP-LMTO) method. The exchange and correlation potential is treated by the local density approximation (LDA). The calculated ground state properties, including, lattice constants, internal parameters, bulk modulus and the pressure derivative of the bulk modulus are in reasonable agreement with the available data. The effect of pressure, up to 40 GPa, on the lattice constants and the internal parameters is also investigated. Using the total energy-strain technique, we have determined the elastic constants Cij, which have not been measured yet. The band structure and the density of states (DOS) show that both materials have a metallic character and Ti 2 InN is more conducting than Ti 2 InC . The analysis of the site and momentum projected densities shows that the bonding is achieved through a hybridization of Ti -atom d states with C ( N )-atom p states. Otherwise, it has been shown that Ti – C and Ti – N bonds are stronger than Ti – In bonds.

Structural and Mechanical Properties of RT2Zn20 and RFe2-xCoxZn20(R=Y, Sm; T=Fe, Ru, Os, Co, Rh and Ir)

2011 ◽  
Vol 689 ◽  
pp. 204-210 ◽  
Author(s):  
Yi Chen ◽  
Jiang Shen
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Mechanical Properties ◽  
Bulk Modulus ◽  
Elastic Constants ◽  
Interatomic Potentials ◽  
Lattice Constants ◽  
Quaternary Compounds ◽  
Cohesive Energies ◽  
Good Agreement

The phase stability, crystal structure and mechanical properties of YT2Zn20 and SmT2Zn20 (T=Fe, Ru, Os, Co, Rh and Ir) compounds have been investigated by using interatomic potentials based on the lattice inversion technique. The calculated lattice constants are in good agreement with the experimental data. The lattice constants increase and Bulk modulus decrease as the transition metal T varies from 3d to 5d. The Y-based compounds with lower energies are more stable than the Sm analogs. Also, the Bulk modulus of YT2Zn20 series are larger than SmT2Zn20 series. Moreover, the mechanical properties of the quaternary compounds YFe2-xCoxZn20 and SmFe2-xCoxZn20­, such as the elastic constants and bulk modulus, have been calculated in this work. The substitution of Co atoms would decrease the cohesive energies and increase the bulk modulus of materials.

PRESSURE DEPENDENCE OF THE ELASTIC CONSTANTS WITH APPLICATION TO MINERALS

2010 ◽  
Vol 24 (31) ◽  
pp. 6091-6098 ◽  
Author(s):  
QUAN LIU
Keyword(s):  
Bulk Modulus ◽  
Elastic Constants ◽  
Pressure Dependence ◽  
First Principle ◽  
Good Accordance

In the present paper, a new relationship for the pressure dependences of elastic constants is developed by using a new expression for the pressure dependence of bulk modulus and a method developed by Grover et al. The proposed relationship is applied to study elastic constants of MgO , NaCl , CaF 2, and CaO . The results obtained for elastic constants are found in good accordance with the experimental and first-principle results.

First-Principle Calculations of the Electronic Structure and Elastic Constants of Arsenic Doped β-SiC

2011 ◽  
Vol 704-705 ◽  
pp. 492-497
Author(s):  
Zong Guo Wang ◽  
Qun Hui ◽  
Nan Pu Cheng ◽  
Chui Lin Wang
Keyword(s):  
Electronic Structure ◽  
Bulk Modulus ◽  
Elastic Constants ◽  
First Principles ◽  
Density Functional ◽  
Energy Levels ◽  
First Principle ◽  
Band Shift ◽  
Functional Theory ◽  
Keywords Arsenic

The electronic structure and elastic constants of arsenic doped β-SiC have been studied by first principles density functional theory (DFT) calculations. The band structure, bulk modulus, and density of states were calculated. We have demonstrated that both the top of the valence and the bottom of the conduction band shift to lower energy levels. However, arsenic doped β-SiC exhibits a non-monotonic variation of the band gap and bulk modulus with the concentration of As. Keywords: arsenic doped β-SiC, electronic structure, elastic constant, first principles

scholarly journals Quantitative Evaluations of Hydrogen Diffusivity in V-X (X = Cr, Al, Pd) Alloy Membranes Based on Hydrogen Chemical Potential

Membranes ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 67
Author(s):  
Asuka Suzuki ◽  
Hiroshi Yukawa
Keyword(s):  
Nearest Neighbor ◽  
Chemical Potential ◽  
Hydrogen Permeability ◽  
First Principle ◽  
Hydrogen Diffusivity ◽  
Hydrogen Atoms ◽  
First Principle Calculations ◽  
Blocking Effects ◽  
Pd Alloy ◽  
Quantitative Evaluations

Vanadium (V) has higher hydrogen permeability than Pd-based alloy membranes but exhibits poor resistance to hydrogen-induced embrittlement. The alloy elements are added to reduce hydrogen solubility and prevent hydrogen-induced embrittlement. To enhance hydrogen permeability, the alloy elements which improve hydrogen diffusivity in V are more suitable. In the present study, hydrogen diffusivity in V-Cr, V-Al, and V-Pd alloy membranes was investigated in view of the hydrogen chemical potential and compared with the previously reported results of V-Fe alloy membranes. The additions of Cr and Fe to V improved the mobility of hydrogen atoms. In contrast, those of Al and Pd decreased hydrogen diffusivity. The first principle calculations revealed that the hydrogen atoms cannot occupy the first-nearest neighbor T sites (T1 sites) of Al and Pd in the V crystal lattice. These blocking effects will be a dominant contributor to decreasing hydrogen diffusivity by the additions of Al and Pd. For V-based alloy membranes, Fe and Cr are more suitable alloy elements compared with Al and Pd in view of hydrogen diffusivity.

scholarly journals Generalization of intrinsic ductile-to-brittle criteria by Pugh and Pettifor for materials with a cubic crystal structure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
O. N. Senkov ◽  
D. B. Miracle
Keyword(s):  
Crystal Structure ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Single Crystal ◽  
Elastic Constants ◽  
Mechanical Analysis ◽  
Quantum Mechanical ◽  
Modulus Ratio ◽  
Cubic Crystal ◽  
The Difference

AbstractTwo classical criteria, by Pugh and Pettifor, have been widely used by metallurgists to predict whether a material will be brittle or ductile. A phenomenological correlation by Pugh between metal brittleness and its shear modulus to bulk modulus ratio was established more than 60 years ago. Nearly four decades later Pettifor conducted a quantum mechanical analysis of bond hybridization in a series of intermetallics and derived a separate ductility criterion based on the difference between two single-crystal elastic constants, C12–C44. In this paper, we discover the link between these two criteria and show that they are identical for materials with cubic crystal structures.

Elastic constants of inflated lobes of dog lungs

1976 ◽  
Vol 40 (4) ◽  
pp. 508-513 ◽  
Author(s):  
S. J. Lai-Fook ◽  
T. A. Wilson ◽  
R. E. Hyatt ◽  
J. R. Rodarte
Keyword(s):  
Bulk Modulus ◽  
Young’S Modulus ◽  
Elastic Constants ◽  
Young's Modulus ◽  
Poisson Ratio ◽  
Inflation Pressure ◽  
Initial State ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Indentation Tests

The elastic constants of dog lungs were determined at various degrees of inflation. In one set of experiments, the lobes were subjected to deformations that approximated the conditions of uniaxial loading. These data, together with the bulk modulus data obtained from the local slope of the pressure-volume curve, were used to determine the two elastic moduli that are needed to describe small nonuniform deformations about an initial state of uniform inflation. The bulk modulus was approximately 4 times the inflation pressure, and Young's modulus was approximately 1.5 times the inflation pressure. In a second set of experiments, lobes were subjected to indentation tests using cylindric punches 1–3 cm in diameter. The value for Young's modulus obtained from these data was slightly higher, approximately twice the inflation pressure. These experiments indicate that the lung is much more easily deformable in shear than in dilatation and that the Poisson ratio for the lung is high, approximately 0.43.

scholarly journals Comparison of the Solid Solution Properties of Mg-RE (Gd, Dy, Y) Alloys with Atomistic Simulation

2008 ◽  
Vol 2008 ◽  
pp. 1-4 ◽  
Author(s):  
Yurong Wu ◽  
Wangyu Hu
Keyword(s):  
Solid Solution ◽  
Bulk Modulus ◽  
Solid Solubility ◽  
Atomistic Simulation ◽  
Molecular Dynamic Simulations ◽  
Solution Properties ◽  
Dynamic Simulations ◽  
Axis Ratio ◽  
Lattice Constants ◽  
Solution Mechanism

Molecular dynamic simulations have been performed to study the solid solution mechanism of Mg100-xREx (RE=Gd,Dy,Y, x=0.5,1,2,3,4  at.%). The obtained results reveal that the additions of Gd, Dy and Y increase the lattice constants of Mg-RE alloys. Also the axis ratio c/a remains unchanged with increase in temperature, restraining the occurrence of nonbasal slip and twinning. Furthermore, it is confirmed that bulk modulus of Mg alloys can be increased remarkably by adding the Gd, Dy, Y, especially Gd, because the solid solubility of Gd in Mg decrease sharply with temperature in comparison with Dy and Y. Consequently, the addition of the RE can enhance the strength of Mg-based alloys, which is in agreement with the experimental results.

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