Supercell and cluster density functional calculations of the thermal stability of the divacancy in germanium

2007 ◽  
Vol 75 (19) ◽  
Author(s):  
C. Janke ◽  
R. Jones ◽  
S. Öberg ◽  
P. R. Briddon
Keyword(s):  
Thermal Stability ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Cluster Density ◽  
Thermal Stability Of

scholarly journals Theory of the Thermal Stability of Silicon Vacancies and Interstitials in 4H–SiC

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 167
Author(s):  
José Coutinho
Keyword(s):  
Thermal Stability ◽  
Fermi Level ◽  
Density Functional ◽  
Dynamic Properties ◽  
Type Material ◽  
Temperature Threshold ◽  
Effect Analysis ◽  
Mobile Species ◽  
Two Stages ◽  
Thermal Stability Of

This paper presents a theoretical study of the electronic and dynamic properties of silicon vacancies and self-interstitials in 4H–SiC using hybrid density functional methods. Several pending issues, mostly related to the thermal stability of this defect, are addressed. The silicon site vacancy and the carbon-related antisite-vacancy (CAV) pair are interpreted as a unique and bistable defect. It possesses a metastable negative-U neutral state, which “disproportionates” into VSi+ or VSi−, depending on the location of the Fermi level. The vacancy introduces a (−/+) transition, calculated at Ec−1.25 eV, which determines a temperature threshold for the annealing of VSi into CAV in n-type material due to a Fermi level crossing effect. Analysis of a configuration coordinate diagram allows us to conclude that VSi anneals out in two stages—at low temperatures (T≲600 °C) via capture of a mobile species (e.g., self-interstitials) and at higher temperatures (T≳1200 °C) via dissociation into VC and CSi defects. The Si interstitial (Sii) is also a negative-U defect, with metastable q=+1 and q=+3 states. These are the only paramagnetic states of the defect, and maybe that explains why it escaped detection, even in p-type material where the migration barriers are at least 2.7 eV high.

DFT study on thermo-elastic properties of Ru2FeZ (Z = Si, Ge, Sn) Heusler alloys

2018 ◽  
Vol 32 (05) ◽  
pp. 1850045 ◽  
Author(s):  
Aneeza Iftikhar ◽  
Afaq Ahmad ◽  
Iftikhar Ahmad ◽  
Muhammad Rizwan
Keyword(s):  
Thermal Stability ◽  
Elastic Properties ◽  
Density Functional ◽  
Heusler Alloys ◽  
Longitudinal Mode ◽  
Transverse Mode ◽  
Functional Theory ◽  
Formation Energies ◽  
Thermal Stability Of ◽  
Temperature Melting

We studied the thermo-elastic properties of Ru2FeZ (Z[Formula: see text]=[Formula: see text]Si, Ge, Sn) Heusler alloys within the framework of density functional theory. Thermo-elastic properties corresponding to elastic modulus, anisotropy, phase stability, elastic wave velocities, thermal stability, Debye temperature, melting temperature, thermal conductivity and formation energy are calculated. The elastic constants C[Formula: see text] predict the structural and dynamical stabilities while the formation energies show thermal stability of the alloys at 0 K. Pugh’s and Poisson’s ratios display the ductile nature of alloys. All alloys are anisotropic and we also observed that Ru2FeSn is the hardest material than Ru2FeSi and Ru2FeGe. Moreover, longitudinal mode of vibrations are also observed and are maximum along [100], [110] and [111] directions than the transverse mode of vibrations.

scholarly journals Controlling Thermal Stability and Volatility of Organogold(I) Compounds for Vapor Deposition with Complementary Ligand Design

2019 ◽  
Author(s):  
Matthew Griffiths ◽  
Zachary Dubrawski ◽  
Goran Bačić ◽  
Jason Masuda ◽  
Achini Japahuge ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Vapor Deposition ◽  
Figure Of Merit ◽  
Density Functional ◽  
Computational Techniques ◽  
Functional Theory ◽  
Design Studies ◽  
X Ray Crystallography ◽  
Compare And Contrast ◽  
Thermal Stability Of

We compare and contrast the volatility and thermal stability of a family of twelve organometallic gold(I) compounds using a combination of X-ray crystallography, thermogravimetric analysis (TGA), and density functional theory (DFT) techniques. Pentafluorophenyl is used as a new ligand for vapor deposition which produces rather low volatility, but very thermally stable compounds when combined with PMe<sub>3</sub> and <i>N</i>,<i>N</i>'-di-<i>tert</i>-butylimidazolidin-2-ylidene. We introduce a precursor figure of merit that can be used to rank precursor usefulness. Using DFT, we find a linear correlation between Au-L bond strength and thermal stability, which demonstrates the power of computational techniques to predict successful synthetic targets for future precursor design studies.

scholarly journals Controlling Thermal Stability and Volatility of Organogold(I) Compounds for Vapor Deposition with Complementary Ligand Design

2019 ◽  
Author(s):  
Matthew Griffiths ◽  
Zachary Dubrawski ◽  
Goran Bačić ◽  
Jason Masuda ◽  
Achini Japahuge ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Vapor Deposition ◽  
Figure Of Merit ◽  
Density Functional ◽  
Computational Techniques ◽  
Functional Theory ◽  
Design Studies ◽  
X Ray Crystallography ◽  
Compare And Contrast ◽  
Thermal Stability Of

We compare and contrast the volatility and thermal stability of a family of twelve organometallic gold(I) compounds using a combination of X-ray crystallography, thermogravimetric analysis (TGA), and density functional theory (DFT) techniques. Pentafluorophenyl is used as a new ligand for vapor deposition which produces rather low volatility, but very thermally stable compounds when combined with PMe<sub>3</sub> and <i>N</i>,<i>N</i>'-di-<i>tert</i>-butylimidazolidin-2-ylidene. We introduce a precursor figure of merit that can be used to rank precursor usefulness. Using DFT, we find a linear correlation between Au-L bond strength and thermal stability, which demonstrates the power of computational techniques to predict successful synthetic targets for future precursor design studies.

Thermal Decomposition of Supersaturated Ti1-xAlxN Solid Solution Synthesized by High-Energy Milling

2016 ◽  
Vol 9 ◽  
pp. 82-89
Author(s):  
Maya Radune ◽  
Michael Zinigrad ◽  
David Fuks ◽  
S. Hayun ◽  
Nachum Frage
Keyword(s):  
Thermal Stability ◽  
Solid Solution ◽  
Spinodal Decomposition ◽  
Density Functional ◽  
Chemical Deposition ◽  
High Energy ◽  
Nucleation And Growth ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
Thermal Stability Of

Supersaturated titanium-aluminum nitride (Ti1-xAlxN) is a very attractive material for a wide range of applications due to its high oxidation and wear resistance accompanied by high strength, hardness, thermal conductivity and thermal shock resistance. Currently, its applications are limited to coatings obtained by physical or chemical deposition. Bulk materials based on Ti1-xAlxN may be fabricated by powder metallurgy approach using powders synthesized by high-energy ball milling (HEBM), which composition corresponds to supersaturated Ti1-xAlxN solid solution. In the present study, thermal stability of the supersaturated Ti1-xAlxN solid solution was investigated. According to the quasi-binary TiN-AlN phase diagram, constructed using density functional theory (DFT) analysis, the concentration ranges, where decomposition takes place through spinodal decomposition or through nucleation and growth, were determined. Experimental study on thermal stability of solid Ti1-xAlxN solution powder was conducted by means of differential scanning calorimetry (DSC), Brunauer-Emmited-Teller (BET) and XRD. The results indicated that spinodal decomposition of Ti1-xAlxN starts at 800°C, while at temperature higher than 1300°C regular decomposition (nucleation and growth) is occur.

Bridging Hydroxyl Groups in Faujasite:  Periodic vs Cluster Density Functional Calculations

1999 ◽  
Vol 103 (19) ◽  
pp. 3772-3777 ◽  
Author(s):  
Jörg-Rüdiger Hill ◽  
Clive M. Freeman ◽  
Bernard Delley
Keyword(s):  
Density Functional Calculations ◽  
Density Functional ◽  
Hydroxyl Groups ◽  
Cluster Density

Investigation of mechanical properties and thermal stability of the thinnest tungsten nanowire by density functional theory

RSC Advances ◽  
2016 ◽  
Vol 6 (2) ◽  
pp. 1158-1168 ◽  
Author(s):  
Hui-Lung Chen ◽  
Shin-Pon Ju ◽  
Ken-Huang Lin ◽  
Jia-Yun Li ◽  
Hsin-Tsung Chen
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Density Functional Theory ◽  
Simulated Annealing ◽  
Density Functional ◽  
Tight Binding ◽  
Functional Theory ◽  
Basin Hopping ◽  
Penalty Algorithm ◽  
Thermal Stability Of

The most stable structure of the thinnest tungsten (W) nanowire with the radius of 1.9 Å was predicted by the simulated annealing basin-hopping method (SABH) with the tight-binding (TB) potential and the penalty algorithm.

Trends in the thermal stability of two-dimensional covalent organic frameworks

2021 ◽  
Author(s):  
Austin M. Evans ◽  
Matthew R. Ryder ◽  
Woojung Ji ◽  
Michael J. Strauss ◽  
Amanda R. Corcos ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Density Functional ◽  
Variable Temperature ◽  
Covalent Organic Frameworks ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Diffuse Reflectance Infrared Spectroscopy ◽  
Diffuse Reflectance Infrared ◽  
Thermal Stability Of

Here, we study the thermal stability of ten 2D covalent organic frameworks using a combination of variable-temperature X-ray diffraction, thermogravimetric analysis, diffuse reflectance infrared spectroscopy, and density-functional theory.

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