Lattice stability and point defect energetics of TiSi2 and TiGe2 allotropes from first-principles calculations

2021 ◽  
Vol 129 (8) ◽  
pp. 085104
Author(s):  
David L. Brown ◽  
Kevin S. Jones ◽  
Simon R. Phillpot
Keyword(s):  
Point Defect ◽  
First Principles ◽  
Lattice Stability ◽  
First Principles Calculations

Electronic structure and point defect concentrations of C11b MoSi2 by first-principles calculations

2014 ◽  
Vol 605 ◽  
pp. 45-50 ◽  
Author(s):  
X.P. Li ◽  
S.P. Sun ◽  
H.J. Wang ◽  
W.N. Lei ◽  
Y. Jiang ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Point Defect ◽  
First Principles ◽  
First Principles Calculations

First-principles Investigations of Point Defect Behavior and Elastic Properties of TiNi Based Alloys

2008 ◽  
Vol 1128 ◽  
Author(s):  
Jian-min Lu ◽  
Qing-miao Hu ◽  
Rui Yang
Keyword(s):  
Elastic Modulus ◽  
Point Defect ◽  
First Principles ◽  
Binary Phase Diagram ◽  
Orbital Method ◽  
Intrinsic Point Defect ◽  
First Principles Calculations ◽  
Potential Approximation ◽  
Early Transition Metal ◽  
Defect Behavior

AbstractFirst-principles calculations by the use of a plane-wave pseudopotential method are performed to investigate intrinsic point defect behavior in TiNi. The results show that TiNi is an antisite type intermetallic compound. The calculated interaction energies between the point defects demonstrate that Ti antisites are attractive to each other whereas Ni antisites are mutually repulsive. The attraction between Ti antisites indicates that excess Ti in TiNi may agglomerate so that a Ti-rich phase can easily precipitate. The repulsion between Ni antisites implies that the excess Ni is of certain solubility in TiNi. This result explains well the asymmetric feature of TiNi field on the binary phase diagram. In order to understand the correlation between the composition dependent elastic modulus and martensitic transformation (MT) temperature, the elastic moduli critical to MT, i.e., c′ and c44, are calculated as a function of the composition of the off-stoichiometric TiNi and a series of ternary TiNi-X alloys, by the use of exact muffin-tin orbital method in combination with coherent potential approximation. It turns out that, generally speaking, the early transition metal (TM) alloying elements in the periodic table increase c′ but decrease c44; the middle ones increase both c′ and c44, whereas the late ones decrease c′ but increase c44. An examination of the theoretical composition dependent elastic modulus and the experimental MT temperature shows that the MT temperature is more sensitive to the variation of c44 than to that of c′.

Understanding and manipulating the intrinsic point defect in α-MgAgSb for higher thermoelectric performance

2016 ◽  
Vol 4 (43) ◽  
pp. 16834-16840 ◽  
Author(s):  
Zihang Liu ◽  
Huiyuan Geng ◽  
Jun Mao ◽  
Jing Shuai ◽  
Ran He ◽  
...  
Keyword(s):  
Point Defect ◽  
First Principles ◽  
Thermoelectric Performance ◽  
Intrinsic Point Defect ◽  
First Principles Calculations ◽  
Recovery Effect ◽  
Hot Press ◽  
Defect Engineering ◽  
Press Temperature

Thorough first-principles calculations reveal that an Ag vacancy is the dominant intrinsic point defect in α-MgAgSb. Point-defect engineering can be realized via rationally controlling the hot press temperature due to the recovery effect.

First-Principles Calculations of Point Defect Formation and Anion Diffusion Mechanisms in the Oxyhydride Ba2ScHO3

2020 ◽  
Author(s):  
Akihide Kuwabara ◽  
Fumitake Takeiri ◽  
Haq Nawaz ◽  
Genki Kobayashi
Keyword(s):  
Point Defect ◽  
First Principles ◽  
Defect Formation ◽  
Diffusion Mechanism ◽  
Layered Perovskite ◽  
First Principles Calculations ◽  
Ion Conductor ◽  
Hydride Ion ◽  
Anion Diffusion ◽  
Hydride Ions

<div>Hydride ion conductors are expected to be a new solid electrolyte for electrochemical devices utilizing hydrogen. La<sub>2-x-y</sub>Sr<sub>x+y</sub>LiH<sub>1-x+y</sub>O<sub>3-y</sub> oxyhydride with a layered perovskite (K<sub>2</sub>NiF<sub>4</sub>-type) structure was discovered as a hydride ion conductor, and it was subsequently reported that Ba<sub>2</sub>ScHO<sub>3</sub> with the same crystal structure is also a hydride ion conductor. The two compounds have different anionic sites occupied by hydride ions. In La<sub>2-x-y</sub>Sr<sub>x+y</sub>LiH<sub>1-x+y</sub>O<sub>3-y</sub>, the hydride ions occupy equatorial anion sites, while the hydride ions are located at apical anion sites in Ba<sub>2</sub>ScHO<sub>3</sub>. This suggests that hydride ions diffuse through rock-salt layers in Ba<sub>2</sub>ScHO<sub>3</sub>. However, the specific diffusion mechanism resulting in ionic conductivity of Ba<sub>2</sub>ScHO<sub>3</sub> has not been clarified yet. In the present study, the point defect</div><div>formation energies and anionic conduction mechanisms of Ba<sub>2</sub>ScHO<sub>3</sub> were systematically analyzed using first-principles calculations. As a result, hydride ionic defects tend to form preferentially in Ba<sub>2</sub>ScHO<sub>3</sub> rather than oxide ions. The migration energies of vacancy, interstitial and interstitialcy mechanisms were evaluated, and the activation energies of hydride ionic diffusion mediated by the vacancy and the interstitialcy processes was found to be the lowest.</div>

scholarly journals Electronic, vibrational, and electron–phonon coupling properties in SnSe2 and SnS2 under pressure

2020 ◽  
Vol 8 (46) ◽  
pp. 16404-16417
Author(s):  
Gyanu Prasad Kafle ◽  
Christoph Heil ◽  
Hari Paudyal ◽  
Elena R. Margine
Keyword(s):  
First Principles ◽  
Lattice Stability ◽  
First Principles Calculations ◽  
Phonon Coupling ◽  
Effect Of Pressure ◽  
Electron Phonon Coupling ◽  
Phonon Properties

First-principles calculations are used to investigate the effect of pressure on lattice stability, electron–phonon properties, and superconductivity in SnSe2 and SnS2.

scholarly journals First-Principles Calculations of Point Defect Formation and Anion Diffusion Mechanisms in the Oxyhydride Ba2ScHO3

2020 ◽  
Author(s):  
Akihide Kuwabara ◽  
Fumitake Takeiri ◽  
Haq Nawaz ◽  
Genki Kobayashi
Keyword(s):  
Point Defect ◽  
First Principles ◽  
Defect Formation ◽  
Diffusion Mechanism ◽  
Layered Perovskite ◽  
First Principles Calculations ◽  
Ion Conductor ◽  
Hydride Ion ◽  
Anion Diffusion ◽  
Hydride Ions

<div>Hydride ion conductors are expected to be a new solid electrolyte for electrochemical devices utilizing hydrogen. La<sub>2-x-y</sub>Sr<sub>x+y</sub>LiH<sub>1-x+y</sub>O<sub>3-y</sub> oxyhydride with a layered perovskite (K<sub>2</sub>NiF<sub>4</sub>-type) structure was discovered as a hydride ion conductor, and it was subsequently reported that Ba<sub>2</sub>ScHO<sub>3</sub> with the same crystal structure is also a hydride ion conductor. The two compounds have different anionic sites occupied by hydride ions. In La<sub>2-x-y</sub>Sr<sub>x+y</sub>LiH<sub>1-x+y</sub>O<sub>3-y</sub>, the hydride ions occupy equatorial anion sites, while the hydride ions are located at apical anion sites in Ba<sub>2</sub>ScHO<sub>3</sub>. This suggests that hydride ions diffuse through rock-salt layers in Ba<sub>2</sub>ScHO<sub>3</sub>. However, the specific diffusion mechanism resulting in ionic conductivity of Ba<sub>2</sub>ScHO<sub>3</sub> has not been clarified yet. In the present study, the point defect</div><div>formation energies and anionic conduction mechanisms of Ba<sub>2</sub>ScHO<sub>3</sub> were systematically analyzed using first-principles calculations. As a result, hydride ionic defects tend to form preferentially in Ba<sub>2</sub>ScHO<sub>3</sub> rather than oxide ions. The migration energies of vacancy, interstitial and interstitialcy mechanisms were evaluated, and the activation energies of hydride ionic diffusion mediated by the vacancy and the interstitialcy processes was found to be the lowest.</div>

First-Principles Calculations of Point Defect Formation and Anion Diffusion Mechanism in Oxyhydride Ba2ScHO3

2020 ◽  
Author(s):  
Akihide Kuwabara ◽  
Fumitake Takeiri ◽  
Haq Nawaz ◽  
Genki Kobayashi
Keyword(s):  
Point Defect ◽  
First Principles ◽  
Defect Formation ◽  
Diffusion Mechanism ◽  
Layered Perovskite ◽  
First Principles Calculations ◽  
Ion Conductor ◽  
Hydride Ion ◽  
Anion Diffusion ◽  
Hydride Ions

<div>Hydride ion conductors are expected to be a new solid electrolyte for electrochemical devices utilizing </div><div>hydrogen. La2-x-ySrx+yLiH1-x+yO3-y oxyhydride with a layered perovskite (K2NiF4-type) structure was </div><div>discovered as a hydride ion conductor, and it was subsequently reported that Ba2ScHO3 with the same </div><div>crystal structure is also a hydride ion conductor. The two compounds have different anionic sites </div><div>occupied by hydride ions. In La2-x-ySrx+yLiH1-x+yO3-y, the hydride ions occupy equatorial anion sites, </div><div>while the hydride ions are located at apical anion sites in Ba2ScHO3. This suggests that hydride ions </div><div>diffuse through rock-salt layers in Ba2ScHO3. However, the specific diffusion mechanism resulting in </div><div>ionic conductivity of Ba2ScHO3 has not been clarified yet. In the present study, the point defect </div><div>formation energies and anionic conduction mechanisms of Ba2ScHO3 were systematically analyzed </div><div>using first-principles calculations. As a result, hydride ionic defects tend to form preferentially in </div><div>Ba2ScHO3 rather than oxide ions. The migration energies of vacancy, interstitial and interstitialcy </div><div>mechanisms were evaluated, and the activation energies of hydride ionic diffusion mediated by the </div><div>vacancy and the interstitialcy processes was found to be the lowest.</div>

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