Microscopic Diffusion Mechanism of Iron in FeAl Revisited by New Methods

1998 ◽  
Vol 527 ◽  
Author(s):  
G. Vogl ◽  
B. Sepiol ◽  
C. Czihak ◽  
R. Rüffer ◽  
R. Weinkamer ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Diffusion Mechanism ◽  
Diffusion Path ◽  
Intermetallic Alloy ◽  
Electron Theory ◽  
New Methods ◽  
Ab Initio Theory ◽  
Ordered Intermetallic ◽  
Diffusion Jump

ABSTRACTThe elementary diffusion jump of Fe atoms in the ordered intermetallic alloy FeAl is studied in a coordinated effort of atomistic experimental techniques, Monte Carlo simulation and abinitio electron theory. The experiment demands that the elementary diffusion jump is a jump into an antistructure site on the Al sublattice which is occupied for a much shorter time than the sites on the Fe sublattice. The diffusion path can be followed by Monte Carlo simulations which can perfectly explain the experiments. Since ab-initio theory yields a very low concentration of Al vacancies it is suggested that correlated jumps of two atoms prevent the creation of a fully developed Al vacancy.

Modeling of Diffusion in Ordered Structures of B2-Type

1998 ◽  
Vol 527 ◽  
Author(s):  
M.G. Ganchenkova ◽  
A.V. Nazarov
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Nearest Neighbor ◽  
Diffusion Mechanism ◽  
Relaxation Technique ◽  
Interatomic Potentials ◽  
Nearest Neighbour ◽  
Ordered Structures ◽  
Activation Barriers ◽  
Static Relaxation

ABSTRACTUsing Monte Carlo simulation, we model the effect of interaction of vacancies on their diffusivities in ordered structures of B2-type. The activation barriers of atom jumps to vacancy are calculated by the static relaxation technique using interatomic potentials for both vacancy exchanges: with nearest-neighbour atoms and next-nearest-neighbour atoms. This is done for all possible positions of the second vacancy. Knowing these barriers it is possible to calculate the jump rates and to model the vacancy migration. The calculations were done for a system with parameters similar to NiAl. The modeling allows to inter the existence of a new diffusion mechanism in ordered structures of B2-type, which could be attributable to dynamic pair of vacancies and vacancy exchanges with next-nearest-neighbor atoms.

scholarly journals Overview of Calculation Methods of Structural Time-Dependent Reliability

2022 ◽  
Vol 2148 (1) ◽  
pp. 012063
Author(s):  
Lisheng Luo ◽  
Xinran Xie ◽  
Yongqiang Zhang ◽  
Wenyuan He
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Simulation Method ◽  
Safety Performance ◽  
Time Dependent ◽  
Structural Performance ◽  
Monte Carlo Simulation Method ◽  
Calculation Methods ◽  
New Methods ◽  
Reliability Method

Abstract Under the action of natural erosion, the strength, durability and other safety performance of structures and elements gradually decrease with time, which has a great impact. To solve the above problem, a series of time-dependent reliability analysis methods were proposed. Based on different structural performance functions, this paper analyzes and discusses different time-dependent reliability theories, including outcrossing-based reliability method, Monte Carlo simulation method, extremum method and other new methods proposed in recent years, which provides reference for later research.

Electron Scattering in Solids

1990 ◽  
Vol 48 (2) ◽  
pp. 4-5
Author(s):  
Ryuichi Shimizu ◽  
Ze-Jun Ding
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Angular Distribution ◽  
Elastic Scattering ◽  
Electron Scattering ◽  
Cross Sections ◽  
Expansion Method ◽  
Electron Excitation ◽  
Partial Wave Expansion ◽  
Backscattered Electrons

Monte Carlo simulation has been becoming most powerful tool to describe the electron scattering in solids, leading to more comprehensive understanding of the complicated mechanism of generation of various types of signals for microbeam analysis.The present paper proposes a practical model for the Monte Carlo simulation of scattering processes of a penetrating electron and the generation of the slow secondaries in solids. The model is based on the combined use of Gryzinski’s inner-shell electron excitation function and the dielectric function for taking into account the valence electron contribution in inelastic scattering processes, while the cross-sections derived by partial wave expansion method are used for describing elastic scattering processes. An improvement of the use of this elastic scattering cross-section can be seen in the success to describe the anisotropy of angular distribution of elastically backscattered electrons from Au in low energy region, shown in Fig.l. Fig.l(a) shows the elastic cross-sections of 600 eV electron for single Au-atom, clearly indicating that the angular distribution is no more smooth as expected from Rutherford scattering formula, but has the socalled lobes appearing at the large scattering angle.

Determination of Stoichiometry of GaAs Component in (Gaas)Ge Epitaxially Grown Thin Films by Electron Microprobe X-Ray Analysis

1990 ◽  
Vol 48 (2) ◽  
pp. 264-265
Author(s):  
D. R. Liu ◽  
S. S. Shinozaki ◽  
R. J. Baird
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Compound Semiconductors ◽  
Energy Dispersive Analysis ◽  
X Ray ◽  
Metastable Alloys ◽  
Lower Voltage

The epitaxially grown (GaAs)Ge thin film has been arousing much interest because it is one of metastable alloys of III-V compound semiconductors with germanium and a possible candidate in optoelectronic applications. It is important to be able to accurately determine the composition of the film, particularly whether or not the GaAs component is in stoichiometry, but x-ray energy dispersive analysis (EDS) cannot meet this need. The thickness of the film is usually about 0.5-1.5 μm. If Kα peaks are used for quantification, the accelerating voltage must be more than 10 kV in order for these peaks to be excited. Under this voltage, the generation depth of x-ray photons approaches 1 μm, as evidenced by a Monte Carlo simulation and actual x-ray intensity measurement as discussed below. If a lower voltage is used to reduce the generation depth, their L peaks have to be used. But these L peaks actually are merged as one big hump simply because the atomic numbers of these three elements are relatively small and close together, and the EDS energy resolution is limited.

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