scholarly journals Effect of Noble Metal Addition on the Disorder Dynamics of Ni3Al by Means of Monte Carlo Simulation

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4832
Author(s):  
J.J. Ramos-Hernandez ◽  
C.D. Arrieta-Gonzalez ◽  
J.G. Chacon-Nava ◽  
E. Porcayo-Palafox ◽  
M. Sanchez-Carrillo ◽  
...  
Keyword(s):  
Activation Energy ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Noble Metal ◽  
Noble Metals ◽  
Activation Energies ◽  
Time Constants ◽  
Metal Addition ◽  
L12 Structure

In this work, the effect of the addition of noble metals on the order–order disorder process of the L12 structure corresponding to the intermetallic Ni3Al is analyzed. Stoichiometric, nonstoichiometric, and quasi-binary compositions doped with noble metals such as Ag, Au, Pd, and Pt (1 at%) were analyzed. It was observed that depending on the composition, there is a modification in the activation energies calculated from the two time constants that characterize the disorder process. The statistic of atomic jumps was typified based on the configuration of the window to be crossed and, with this, it was identified that the origin of the negative activation energy of the long disorder process is due to an increase in the corresponding energy of the AlAl-Ni jump through unnatural windows.

scholarly journals Kinetic Monte Carlo Simulation of Clustering in an Al-Mg-Si-Cu Alloy

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4523
Author(s):  
Qilu Ye ◽  
Jianxin Wu ◽  
Jiqing Zhao ◽  
Gang Yang ◽  
Bin Yang
Keyword(s):  
Activation Energy ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Complex Interaction ◽  
Cu Alloy ◽  
Cu Alloys ◽  
Simulation Results ◽  
Small Clusters ◽  
First Time

The mechanism of the clustering in Al-Mg-Si-Cu alloys has been a long-standing controversial issue. Here, for the first time, the mechanism of the clustering in the alloy was investigated by a Kinetic Monte Carlo (KMC) approach. In addition, reversion aging (RA) was carried out to evaluate the simulation results. The results showed that many small-size clusters formed rapidly in the early stages of aging. With the prolongation of aging time, the clusters merged and grew. The small clusters formed at the beginning of aging in Al-Mg-Si-Cu alloy were caused by initial vacancies (quenching vacancies). The merging and decomposition of the clusters were mainly caused by the capturing of vacancies, and the clusters had a probability to decompose before reaching a stable size. After repeated merging and decomposition, the clusters reach stability. During RA, the complex interaction between the cluster merging and decomposition leaded to the partial irregular change of the hardness reduction and activation energy.

MONTE CARLO SIMULATION OF TEMPERATURE-PROGRAMMED DESORPTION CO/Cu(110) AND CO2/Cu(100) SYSTEMS

2004 ◽  
Vol 11 (02) ◽  
pp. 137-143 ◽  
Author(s):  
KH. ZAKERI ◽  
A. DASHTI
Keyword(s):  
Activation Energy ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Excellent Agreement ◽  
Temperature Programmed Desorption ◽  
High Order ◽  
Kinetics And Mechanism ◽  
Lateral Interaction ◽  
Desorption Rate ◽  
Temperature Programmed

In this investigation, we have studied the kinetics and mechanism of desorption of CO from the Cu (110) surface using a new Monte Carlo simulation and putting emphasis on high order lateral interaction. According to our simulated TPD spectra, for β=10 K/s the maximum desorption rate occurs at Tm=218.6 K. Furthermore, analysis of simulated TPD spectra of CO desorption shows that it is strongly lateral-interactive and results an activation energy of CO desorption from Cu (110) that is Ed=66.6 Kj/mol. These simulated results are compared with other reported results and show excellent agreement. After that we have investigated the kinetics and mechanism of desorption of CO 2 from the Cu (100) surface using a Monte Carlo simulation. According to our simulated TPD spectra, for β=0.5 K/s the maximum desorption rate occurs at Tm=89.7 K. Analysis of simulated TPD spectra of CO 2 desorption shows that it is not strongly lateral-interactive and results in an activation energy of CO desorption from Cu (100) that is Ed=25.2 Kj/mol. Finally, the CO / Cu (110) system is compared with the CO 2/ Cu (100) system.

Hydrogen–Water Deuterium Exchange over Graphon Supported Group VIII Noble Metals

1973 ◽  
Vol 51 (24) ◽  
pp. 4031-4037 ◽  
Author(s):  
Norman Henry Sagert ◽  
Rita Mary Louise Pouteau
Keyword(s):  
Activation Energy ◽  
Atomic Number ◽  
Noble Metals ◽  
Activation Energies ◽  
Group Viii ◽  
Surface Exchange ◽  
Hydrogen Water ◽  
Temperature Range ◽  
The Third ◽  
Specific Activities

Specific activities of Group VIII noble metals supported on Graphon have been determined for hydrogen–water deuterium exchange. Metal surface areas, which are required to calculate specific activities, were measured by hydrogen chemisorption, and by reaction of hydrogen with chemisorbed oxygen. For the second triad metals, ruthenium, rhodium, and palladium, and in the temperature range 140 to 225 °C, the variation of activity was Ru < Rh > Pd. For the third triad metals, osmium, iridium, and platinum, the variation of activities was Os < Ir < Pt in the same range of temperature. Apparent activation energies were measured over this temperature range, and orders of reaction with respect to hydrogen and water were measured at 160 °C (200 °C for Pt). From these data, activation energies for the surface exchange reaction were calculated. In the second triad the activation energies decrease slightly with increasing atomic number, but in the third triad they decrease quite markedly with increasing atomic number. A good correlation was obtained between the activation energy for surface exchange and the thermionic work function of the metal. This supports our earlier suggestion that Graphon is able to donate electrons to the metal and thus lower the activation energy for the surface exchange.

Tracer Diffusion and Ordering in FCC Structures - Stochastic Kinetic Mean-Field Method vs. Kinetic Monte Carlo

2018 ◽  
Vol 383 ◽  
pp. 59-65 ◽  
Author(s):  
Volodymyr Bezpalchuk ◽  
Rafal Abdank-Kozubski ◽  
Mykola Pasichnyy ◽  
Andriy Gusak
Keyword(s):  
Activation Energy ◽  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Mean Field ◽  
Field Method ◽  
Activation Energies ◽  
Tracer Diffusion ◽  
Atomistic Modelling ◽  
Fcc Alloys ◽  
Diffusion Activation

Recently developed method of atomistic modelling (SKMF) is applied to order-disorder transitions in FCC alloys and to tracer diffusion in the ordered L12 structure. Results correlate with Kinetic Mote-Carlo modelling. Difference of diffusion activation energies of two species is found. Activation energy of ordering is close to one of minority component diffusion.

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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