scholarly journals A critical assessment of interatomic potentials for modelling lattice defects in forsterite Mg$$_2$$SiO$$_4$$ from 0 to 12 GPa

2021 ◽  
Vol 48 (12) ◽  
Author(s):  
Pierre Hirel ◽  
Jean Furstoss ◽  
Philippe Carrez
Keyword(s):  
Upper Mantle ◽  
Stacking Faults ◽  
Elastic Stiffness ◽  
Elastic Wave Velocity ◽  
Critical Assessment ◽  
Interatomic Potentials ◽  
Planar Defects ◽  
Material Density ◽  
Lattice Constants ◽  
Stacking Fault Energies

AbstractFive different interatomic potentials designed for modelling forsterite Mg$$_2$$ 2 SiO$$_4$$ 4 are compared to ab initio and experimental data. The set of tested properties include lattice constants, material density, elastic wave velocity, elastic stiffness tensor, free surface energies, generalized stacking faults, neutral Frenkel and Schottky defects, in the pressure range $$0-12$$ 0 - 12  GPa relevant to the Earth’s upper mantle. We conclude that all interatomic potentials are reliable and applicable to the study of point defects. Stacking faults are correctly described by the THB1 potential, and qualitatively by the Pedone2006 potential. Other rigid-ion potentials give a poor account of stacking fault energies, and should not be used to model planar defects or dislocations. These results constitute a database on the transferability of rigid-ion potentials, and provide strong physical ground for simulating diffusion, dislocations, or grain boundaries.

Crystalline perfection of chemical vapor deposited diamond films

1990 ◽  
Vol 5 (8) ◽  
pp. 1591-1594 ◽  
Author(s):  
A. V. Hetherington ◽  
C. J. H. Wort ◽  
P. Southworth
Keyword(s):  
Grain Boundaries ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Stacking Faults ◽  
Chemical Vapor ◽  
Cvd Diamond ◽  
Growth Conditions ◽  
Crystalline Perfection ◽  
Planar Defects ◽  
Chemical Vapor Deposited

The crystalline perfection of microwave plasma assisted chemical vapor deposited (MPACVD) diamond films grown under various conditions has been examined by TEM. Most CVD diamond films thus far reported contain a high density of defects, predominantly twins and stacking faults on {111} planes. We show that under appropriate growth conditions, these planar defects are eliminated from the center of the crystallites, and occur only at grain boundaries where the growing crystallites meet.

scholarly journals Stacking faults in β-Ga2O3 crystals observed by X-ray topography

2018 ◽  
Vol 51 (5) ◽  
pp. 1372-1377 ◽  
Author(s):  
Hirotaka Yamaguchi ◽  
Akito Kuramata
Keyword(s):  
Crystal Growth ◽  
Partial Dislocation ◽  
Structural Model ◽  
Stacking Faults ◽  
Elastic Instability ◽  
Planar Defects ◽  
X Ray ◽  
Self Energy ◽  
Unique Structural Feature ◽  
Edge Component

Planar defects in (\overline{2}01)-oriented β-Ga2O3 wafers were studied using X-ray topography. These planar defects were rectangular with dimensions of 50–150 µm, and the X-ray topography analysis revealed that they were stacking faults (SFs) enclosed by a single partial dislocation loop on the (\overline{2}01) plane. The SF formation was found to be supported by a unique structural feature of the (\overline{2}01) plane as a slip plane; the (\overline{2}01) plane consists of close-packed octahedral Ga and O layers, allowing slips to form SFs. Vacancy arrays along the b axis in the octahedral Ga layer reduce the self-energy of the edge component in the partial dislocation extending along the b axis. It is speculated that the SFs occur during the crystal growth process for unknown reasons and then recover owing to elastic instability after initially increasing in size as crystal growth proceeds. Based on this analysis, a structural model for the SFs is proposed.

Defects in Germanium Nanocrystals Produced by Ion Implantation

2013 ◽  
Vol 709 ◽  
pp. 148-152
Author(s):  
Yu Juan Zhang ◽  
Lei Shang
Keyword(s):  
Electron Microscopy ◽  
Light Emission ◽  
Stacking Faults ◽  
Implantation Dose ◽  
Defect Structures ◽  
High Temperature Annealing ◽  
Planar Defects ◽  
Transmission Electron ◽  
Microstructural Defects ◽  
Germanium Nanocrystals

Germanium nanocrystals (Ge-nc) were produced by the implantation of Ge+ into a SiO2 film deposited on (100) Si, followed by a high-temperature annealing. High-resolution transmission electron microscopy (HRTEM) has been used to investigate the defect structures inside the Ge-nc produced by different implantation doses (1×1016, 2×1016, 4×1016 and 8×1016 cm-2). It has been found that the planar defects such as nanotwins and stacking faults (SFs) are dominant in Ge-nc (60%) for the samples with implantation doses higher than 2×1016 cm-2, while for the sample with an implantation dose lower than 1×1016 cm-2, fewer planar defects are observed in the Ge-nc (20%). The percentages of nanotwins in the planar defects are 87%, 77%, 67% and 60% in four samples, respectively. The twinning structures include single twins, double twins and multiple twins. We also found that there are only SFs in some nanocrystals, and in others the SFs coexist with twins. These microstructural defects are expected to play an important role in the light emission from the Ge-nc.

ON THE ROLE OF STACKING FAULTS IN SOME PROBLEMS OF GLIDE AND TWINNING IN CUBIC METALS

1967 ◽  
Vol 45 (2) ◽  
pp. 481-492 ◽  
Author(s):  
B. Escaig ◽  
G. Fontaine ◽  
J. Friedel
Keyword(s):  
Point Defects ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Dislocation Network ◽  
Thermal Variation ◽  
Temperature Dependent ◽  
Cubic Metals ◽  
Thermally Activated ◽  
Stacking Fault Energies

The possible role of stacking faults is discussed in some problems of glide and twinning of cubic metals, especially at low temperatures.The first part analyzes a model for the thermal variation of macroyield in b.c.c. metals. If one assumes that the dislocations of such metals split along either the (110) or the (112) planes, the screw dislocations will be sessile. The strong temperature variation of macroyield could be due to the thermally activated slip of such screws, previously developed at lower stresses during the less temperature-dependent microyield. Reasonably high stacking-fault energies are required for satisfactory numerical fits.The second part studies the influence of a dense dislocation network on the propagation of a stacking fault. The friction force acting on the partial that propagates the fault must be taken into account when deducing a stacking-fault energy from the stress at which stacking faults develop in a strongly work-hardened (f.c.c.) metal. The trails of dipoles left at each tree crossed should prevent any creation of point defects; they should lead, after the faults have propagated some length, to its multiplication into a twin or martensitic lamella. The analogies with problems of slip bauds and dipole formation in easy glide are stressed.

The Calculation of Stiffness for Semiconductor Components

2009 ◽  
Author(s):  
Mohamed Gaith ◽  
Imad Alhayek
Keyword(s):  
Bulk Modulus ◽  
Elastic Stiffness ◽  
Quantitative Comparison ◽  
Lattice Constants ◽  
Electro Optic ◽  
Semiconductor Compounds ◽  
Cubic System ◽  
Tensor Basis ◽  
Norm Ratio ◽  
Anisotropy Degree

In this study, the correlation between macroscopic and microscopic properties of the II-IV semiconductor compounds CdX (X = S, Se, Te) is investigated. Based on constructing orthonormal tensor basis elements using the form-invariant expressions, the elastic stiffness for cubic system materials is decomposed into two parts; isotropic (two terms) and anisotropic parts. A new scale for measuring the overall elastic stiffness of these compounds is introduced and its correlation with the calculated bulk modulus and lattice constants is analyzed. The overall elastic stiffness is calculated and found to be directly proportional to bulk modulus and inversely proportional to lattice constants. A scale quantitative comparison of the contribution of the anisotropy to the elastic stiffness and to measure the anisotropy degree in an anisotropic material is proposed using the Norm Ratio Criteria (NRC). It is found that CdS is the nearest to isotropy (or least anisotropic) while CdTe is the least near to isotropy (or nearest to anisotropic) among these compounds. The norm and norm ratios are found to be very useful for selecting suitable materials for electro-optic devices, transducers, modulators, acousto-optic devices.

Electronic and elastic properties of AIIB2IIIC4VI defect-chalcopyrite semiconductors

2019 ◽  
Vol 33 (28) ◽  
pp. 1950340 ◽  
Author(s):  
S. Chandra ◽  
Anita Sinha ◽  
V. Kumar
Keyword(s):  
Debye Temperature ◽  
Elastic Properties ◽  
Density Functional ◽  
Elastic Stiffness ◽  
Lattice Constants ◽  
Chalcopyrite Semiconductors ◽  
Principle Density Functional Theory ◽  
Experimental Values ◽  
G Ratio ◽  
First Time

The electronic and elastic properties of [Formula: see text] defect-chalcopyrite semiconductors have been studied using first-principle density functional theory (DFT) calculations. The lattice constants, energy band gap, elastic stiffness constants, bulk modulus, shear modulus, shear anisotropy factor, Young’s modulus, Debye temperature, Poisson’s ratio and B/G ratio have been computed. The values of elastic constants of 14 defect-chalcopyrites and Debye temperature for 18 compounds have been reported for the first time. The obtained results are in reasonable agreement with the experimental values in few cases where experiments are performed and reported values.

Effects of Angular Dependent Terms in the Interatomic Potential on Defect Properties in TiAl

1994 ◽  
Vol 364 ◽  
Author(s):  
Julia Panova ◽  
Diana Farkas
Keyword(s):  
Interatomic Potential ◽  
Stacking Faults ◽  
Core Structure ◽  
Interatomic Potentials ◽  
The Core ◽  
Embedded Atom ◽  
Dependent Term

AbstractInteratomic potentials of the Embedded Atom and Embedded Defect types were used to study the effect of the angular dependent term in the Embedded Defect potential on the properties of defects in TiAl. The defect properties were computed with interatomic potentials developed with and without angular dependent terms. It was found that the inclusion of the angular dependent terms tends to increase the energies of the APB’s and lower the energies of stacking faults. The effects of the angular term on the relaxation around vacancies and antisites in TiAl was also studied, as well as the core structure of several dislocations in this compound.

Microstructure observations of silicon carbide nanorods

2000 ◽  
Vol 15 (9) ◽  
pp. 2020-2026 ◽  
Author(s):  
H. Y. Peng ◽  
X. T. Zhou ◽  
H. L. Lai ◽  
N. Wang ◽  
S. T. Lee
Keyword(s):  
Vapor Deposition ◽  
Stacking Faults ◽  
Chemical Vapor ◽  
High Resolution Electron Microscopy ◽  
Growth Direction ◽  
Planar Defects ◽  
Resolution Electron ◽  
Short Nanorods ◽  
Hot Filament ◽  
Nanorod Growth

The microstructures of β-SiC nanorods synthesized by hot-filament chemical vapor deposition were studied in detail by high-resolution electron microscopy. Two distinct types of nanorods were identified. The longer nanorods (lengths > 0.1 mm) contained globules at their tips and a relatively low density of stacking faults perpendicular to their [111] growth direction. It was also observed that SiC nanorods that grew along [100] direction contained no planar defects. Meanwhile, Ni was found to be an effective catalyst for SiC nanorod growth. The short nanorods (lengths < 50 nm), which contained no globules at their ends, can grow along [111], [100], or [112] direction. The growth of these nanorods was interpreted by a two-dimensional vapor–solid mechanism.

The Measurement of Overall Elastic Stiffness and Bulk Modulus in Anisotropic Materials: Semiconductors

2009 ◽  
Author(s):  
Mohamed S. Gaith ◽  
I. Alhayek
Keyword(s):  
Bulk Modulus ◽  
Elastic Stiffness ◽  
Quantitative Comparison ◽  
Lattice Constants ◽  
Electro Optic ◽  
Semiconductor Compounds ◽  
Degree Of Anisotropy ◽  
Cubic System ◽  
Tensor Basis ◽  
Norm Ratio

In this study, the correlation between macroscopic and microscopic properties of the II-IV semiconductor compounds ZnX (X = S, Se, Te) is investigated. Based on constructing orthonormal tensor basis elements using the form-invariant expressions, the elastic stiffness for cubic system materials is decomposed into two parts; isotropic (two terms) and anisotropic parts. A scale for measuring the overall elastic stiffness of these compounds is introduced and its correlation with the calculated bulk modulus and lattice constants is analyzed. The overall elastic stiffness is calculated and found to be directly proportional to bulk modulus and inversely proportional to lattice constants. A scale quantitative comparison of the contribution of the anisotropy to the elastic stiffness and to measure the degree of anisotropy in an anisotropic material is proposed using the Norm Ratio Criteria (NRC). It is found that ZnS is the nearest to isotropy (or least anisotropic) while ZnTe is the least isotropic (or nearest to anisotropic) among these compounds. The norm and norm ratios are found to be very useful for selecting suitable materials for electro-optic devices, transducers, modulators, acousto-optic devices.

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