Ab-Initio Investigations of Surfaces and Grain Boundaries in Germanium

1992 ◽  
pp. 169-175
Author(s):  
M. C. Payne ◽  
G. P. Francis ◽  
M. Needels ◽  
E. Tarnow ◽  
P. Dallot ◽  
...  
Keyword(s):  
Ab Initio ◽  
Grain Boundaries

Atomic and Electronic Structure of Boron-Doped Diamond Grain Boundaries Studied by Arhvtem and ab-Initio Calculation

2003 ◽  
Vol 764 ◽  
Author(s):  
Hiroyuki Togawa ◽  
Hideki Ichinose
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Ab Initio Calculation ◽  
Structure Model ◽  
Boron Doped Diamond ◽  
Boron Doped ◽  
Transmission Electron ◽  
Diamond Grain ◽  
Electron Energy Loss ◽  
Atomic And Electronic Structure

AbstractAtomic resolution high-voltage transmission electron microscopy and electron energy loss spectroscopy were performed on grain boundaries of boron-doped diamond, cooperated with the ab-initio calculation. Segregated boron in the {112}∑3 boundary was caught by the EELS spectra. The change in atomic structure of the segregated boundary was successfully observed from the image by ARHVTEM. Based on the ARHVTEM image, a segregted structure model was proposed.

Structure and Stability of Grain Boundaries in Molybdenum with Segregated Carbon Impurities

1999 ◽  
Vol 578 ◽  
Author(s):  
R. Janisch ◽  
T. Ochs ◽  
A. Merkle ◽  
C. Elsässer
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Carbide Phases ◽  
Carbon Impurities ◽  
Transmission Electron ◽  
Local Density Functional Theory ◽  
Symmetrical Tilt

AbstractThe segregation of interstitial impurities to symmetrical tilt grain boundaries (STGB) in bodycentered cubic transition metals is studied by means of ab-initio electronic-structure calculations based on the local density functional theory (LDFT). Segregation energies as well as changes in atomic and electronic structures at the ΣE5 (310) [001] STGB in Mo caused by segregated interstitial C atoms are investigated. The results are compared to LDFT data obtained previously for the pure Σ5 (310) [001] STGB in Mo. Energetic stabilities and structural parameters calculated ab initio for several crystalline Molybdenum Carbide phases with cubic, tetragonal or hexagonal symmetries and different compositions, MoCx, are reported and compared to recent high-resolution transmission electron microscopy (HRTEM) observations of MoCx, intergranular films and precipitates formed by C segregation to a Σ5 (310) [001] STGB in a Mo bicrystal.

Ab initio perspective of the 〈110〉 symmetrical tilt grain boundaries in bcc Fe: application of local energy and local stress

2014 ◽  
Vol 49 (11) ◽  
pp. 3980-3995 ◽  
Author(s):  
Somesh Kr. Bhattacharya ◽  
Shingo Tanaka ◽  
Yoshinori Shiihara ◽  
Masanori Kohyama
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Local Stress ◽  
Local Energy ◽  
Symmetrical Tilt

Ab Initio Calculations for Grain Boundaries in Covalent Ceramics

1996 ◽  
Vol 458 ◽  
Author(s):  
Masanori Kohyama
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Grain Boundaries ◽  
First Principles ◽  
Localized States ◽  
Edge States ◽  
Bulk Diamond ◽  
First Time ◽  
Bulk Band

ABSTRACTAb initio calculations of grain boundaries in SiC have been performed for the first time by using the first-principles molecular dynamics (FPMD) method. Four-fold coordinated models of polar and non-polar interfaces of the {122}Σ = 9 boundary in SiC have been examined. Interfacial C-C and Si-Si wrong bonds have bond lengths and bond charges similar to those in bulk diamond and Si. The C-C bonds generate greatly localized states at the valence-band edges, which have features similar to the bulk band-edge states of diamond. The wrong bonds have significant effects on the properties of grain boundaries in SiC.

scholarly journals Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Lina Yang ◽  
Austin J. Minnich
Keyword(s):  
Thermal Conductivity ◽  
Monte Carlo ◽  
Ab Initio ◽  
Grain Boundaries ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Computational Study ◽  
Phonon Transport ◽  
Nanocrystalline Si

Abstract Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials.

Ab initio tensile tests of grain boundaries in the fcc crystals of Ni and Co with segregated sp-impurities

2016 ◽  
Vol 669 ◽  
pp. 218-225 ◽  
Author(s):  
M. Černý ◽  
P. Šesták ◽  
P. Řehák ◽  
M. Všianská ◽  
M. Šob
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Tensile Tests
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