Details of the Formation of Superstructures in the Process of Ordering in Cu-Pt Alloys

2013 ◽  
Vol 592-593 ◽  
pp. 321-324 ◽  
Author(s):  
Mikhail Starostenkov ◽  
Alexandra Chaplygina ◽  
Veronika Romanenko

Alloys of Cu-Pt [1] are of interest for research, since the phase transitions "order - disorder" at different concentrations of components form several types of superstructures. In the alloy Cu3Pt the ordering L12 superstructure formed on the basis of fcc lattice. In the ordering of the fcc lattice of the disordered solid solution the equiatomic composition transformed into the L11 superstructure with an rhombohedral crystal lattice (a state with an L11, whose angles α, β, and γ are other than π/2). A CuPt3 in an ordered state has an L13 superstructure (a state with an L13, whose angles α, β, and γ are other than π/2). A possible existence of an ordered phase containing 20 at.% Pt was reported in the literature [2], which corresponds to the composition of Cu4Pt (type of superstructure was not defined). In other sources, an occurrence of an ordered compound, Cu7Pt, was predicted, containing 12.5 at.% Pt [3]. Computer experiments performed on the Monte Carlo method, showed that the alloys of the Cu - Pt different composition components undergo phase transformations "disorder - order" from the FCC to the structures of different symmetry [4,11]. This paper presents the results of a study of the structural transformations in the alloys Cu3Pt, CuPt, CuPt3 (superstructure L12, L11, L13), containing shear antiphase boundaries (APB) in the planes {111}.

Author(s):  
С.А. Желтов ◽  
Н.Н. Чупятов

Процесс нанесения покрытий на поверхности является одним из важнейших при нанесении защитных слоев. Особенно актуальным является метод молекулярно-лучевой эпитаксии, который применяют, например, для нанесения покрытий металлов и полимеров на металлические поверхности. Однако при производстве установок необходимо провести много предварительных экспериментов для получения максимально однородных напыленных поверхностей: размеры кювет, уровень расплава в кювете, расстояния до напыляемой поверхности и расположения системы кювет. Упрощением проведения этих реальных экспериментов является метод Монте-Карло. Моделируя компьютерные эксперименты с предполагаемыми параметрами установки, можно быстро получить необходимый результат с высокой точностью. В каждом компьютерном эксперименте разыгрывался вылет N = 108 частиц (атомов, молекул), что обеспечивало получение всех результатов с высокой точностью. Было установлено, что результаты расчетов не зависят от масс частиц. Анализ полученных данных позволил установить, что частицы, испарявшиеся с поверхности расплава по равновероятному закону и по закону косинуса, имеют близкие распределения, отличающиеся не более чем на 10%. Увеличение расстояния от верхнего края пластины до напыляемой плоскости с расстояния G = 0,01 м до расстояния G = 0,05 м приводит к тому, что плотность распределения для первого случая, имеющая значительный максимум около середины кюветы, становится практически равномерным распределением во втором случае. Применение метода Монте-Карло для процессов напыления в вакууме эффективно использовать не только для плоских поверхностей, но и на поверхности произвольных форм, например, цилиндрических. The coating process on surfaces is one of the most important in the application of protective layers. Particularly relevant is the method of molecular beam epitaxy, which is used, for example, for the deposition of coatings of metals and polymers on metal surfaces. However, in the manufacture of installations, it is necessary to carry out many preliminary experiments to obtain the most homogeneous sprayed surfaces: the dimensions of the cuvettes, the level of the melt in the cuvette, the distance to the sprayed surface and the location of the cuvette system. A simplification of these real-world experiments is the Monte Carlo method. By simulating computer experiments with the expected parameters of the installation, it is possible to quickly obtain the required result with high accuracy. In each computer experiment, the emission of N = 108 particles (atoms, molecules) was played, which ensured obtaining all results with high accuracy. It was found that the calculation results do not depend on the particle masses. An analysis of the data obtained made it possible to establish that the particles evaporated from the surface of the melt according to the equiprobable law and according to the cosine law have similar distributions differing by no more than 10%. An increase in the distance from the upper edge of the plate to the sprayed plane from a distance of G = 0.01 m to a distance of G = 0.05 m leads to the fact that the distribution density for the first case, which has a significant maximum near the middle of the cell, becomes an almost uniform distribution in the second case. ... The use of the Monte Carlo method for vacuum deposition processes can be effectively used not only for flat surfaces, but also on surfaces of arbitrary shapes, for example, cylindrical ones.


2020 ◽  
Vol 2020 (4) ◽  
pp. 25-32
Author(s):  
Viktor Zheltov ◽  
Viktor Chembaev

The article has considered the calculation of the unified glare rating (UGR) based on the luminance spatial-angular distribution (LSAD). The method of local estimations of the Monte Carlo method is proposed as a method for modeling LSAD. On the basis of LSAD, it becomes possible to evaluate the quality of lighting by many criteria, including the generally accepted UGR. UGR allows preliminary assessment of the level of comfort for performing a visual task in a lighting system. A new method of "pixel-by-pixel" calculation of UGR based on LSAD is proposed.


Author(s):  
V.A. Mironov ◽  
S.A. Peretokin ◽  
K.V. Simonov

The article is a continuation of the software research to perform probabilistic seismic hazard analysis (PSHA) as one of the main stages in engineering seismic surveys. The article provides an overview of modern software for PSHA based on the Monte Carlo method, describes in detail the work of foreign programs OpenQuake Engine and EqHaz. A test calculation of seismic hazard was carried out to compare the functionality of domestic and foreign software.


2019 ◽  
Vol 20 (12) ◽  
pp. 1151-1157 ◽  
Author(s):  
Alla P. Toropova ◽  
Andrey A. Toropov

Prediction of physicochemical and biochemical behavior of peptides is an important and attractive task of the modern natural sciences, since these substances have a key role in life processes. The Monte Carlo technique is a possible way to solve the above task. The Monte Carlo method is a tool with different applications relative to the study of peptides: (i) analysis of the 3D configurations (conformers); (ii) establishment of quantitative structure – property / activity relationships (QSPRs/QSARs); and (iii) development of databases on the biopolymers. Current ideas related to application of the Monte Carlo technique for studying peptides and biopolymers have been discussed in this review.


Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 745
Author(s):  
Dimitrios Meimaroglou ◽  
Sandrine Hoppe ◽  
Baptiste Boit

The kinetics of the hydrolysis and polycondensation reactions of saccharides have made the subject of numerous studies, due to their importance in several industrial sectors. The present work, presents a novel kinetic modeling framework that is specifically well-suited to reacting systems under strict moisture control that favor the polycondensation reactions towards the formation of high-degree polysaccharides. The proposed model is based on an extended and generalized kinetic scheme, including also the presence of polyols, and is formulated using two different numerical approaches, namely a deterministic one in terms of the method of moments and a stochastic kinetic Monte Carlo approach. Accordingly, the most significant advantages and drawbacks of each technique are clearly demonstrated and the most fitted one (i.e., the Monte Carlo method) is implemented for the modeling of the system under different conditions, for which experimental data were available. Through these comparisons it is shown that the model can successfully follow the evolution of the reactions up to the formation of polysaccharides of very high degrees of polymerization.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Jerzy Bienek ◽  
Piotr Komarnicki ◽  
Jerzy Detyna

AbstractThis article presents the main problems associated with cereal harvesting in sloping areas. The presented innovative aerodynamic system supporting the separating unit of combine harvester can be one of the ways to counteract the negative effects of harvesting machines work on slopes. The Monte Carlo numerical method, presented in this article, was applied in the optimization of an aerodynamic sieve separation process on an inclined terrain. The given variables are the transverse slope of separator α (of the sieve), longitudinal slope β and the output of the main and side fans. The Monte Carlo method makes it possible to determine an optimized set of parameters (α = 10°, β = 2.8°, δ = 9°), the output of the main fan (0.67 m3 s−1) and the output of the side fan (1.86 m3 s−1), allowing to obtain the best indicator values of 2.1% grain loss and 97.5% grain purity.


1999 ◽  
Vol 72 (1) ◽  
pp. 68-72
Author(s):  
M. Yu. Al’es ◽  
A. I. Varnavskii ◽  
S. P. Kopysov

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