scholarly journals Distributions of Two Atoms Collisions over the Surface of the Condensed Phase

2021 ◽  
Vol 248 ◽  
pp. 01022
Author(s):  
Sergey Zheltov ◽  
Leonid Pletnev

The processes of heat and mass transfer are closely related to the evaporation of a substance from the surface of the condensed phase. The interaction of outgoing molecules from the surface of the condensed phase with condensed phase molecules plays a fundamental role. A simpler case of evaporation is the departure of atoms from the surface of the condensed phase, i.e. the atoms overcome the potential barrier on the surface of the condensed phase. Depending on the evaporation rate, a Knudsen layer appears above the surface of the condensed phase. In this paper, based on the model of rigid spheres, the density distributions of the collision distances and the average values of the collision distances of two atoms emitted simultaneously from the surface of the condensed phase above the surface are analyzed. Distributions of the collision distance depending on the surface temperature, the size of the potential barrier, and the size of the evaporation area are obtained. Computer experiments were performed using the Monte Carlo method. To obtain the results of numerical simulation, a parallel algorithm adapted to calculations on graphics processors with CUDA technology was developed.

2016 ◽  
Vol 6 (1) ◽  
pp. 79-90
Author(s):  
Łukasz Syrocki ◽  
Grzegorz Pestka

AbstractThe ready to use set of functions to facilitate solving a generalized eigenvalue problem for symmetric matrices in order to efficiently calculate eigenvalues and eigenvectors, using Compute Unified Device Architecture (CUDA) technology from NVIDIA, is provided. An integral part of the CUDA is the high level programming environment enabling tracking both code executed on Central Processing Unit and on Graphics Processing Unit. The presented matrix structures allow for the analysis of the advantages of using graphics processors in such calculations.


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.


2018 ◽  
Vol 6 (3) ◽  
pp. 1-17 ◽  
Author(s):  
Masato Konishi ◽  
Seiya Okubo ◽  
Tetsuro Nishino ◽  
Mitsuo Wakatsuki

This article describes how computer Daihinmin involves playing Daihinmin, a popular card game in Japan, by using a player program. Because strong player programs of Computer Daihinmin use machine-learning techniques, such as the Monte Carlo method, predicting the program's behavior is difficult. In this article, the authors extract the features of the player program through decision tree analysis. The features of programs are extracted by generating decision trees based on three types of viewpoints. To show the validity of their method, computer experiments were conducted. The authors applied their method to three programs with relatively obvious behaviors, and they confirmed that the extracted features were correct by observing real behaviors of the programs.


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}.


1959 ◽  
Vol 81 (2) ◽  
pp. 254-261
Author(s):  
J. H. Milsum

The problem is considered of minimizing total costs of a regulator subject to both a steady reference input and a statistical load disturbance. A binary error criterion is used which directly relates the error magnitude to the economic penalty entailed by the error. In contrast it is not easy to relate the mean-square error to economic penalty. Experimental work shows that the amplitude probability density distributions in saturating loops are altered sufficiently from the Gaussian that the statistical linearization technique does not predict results with satisfactory accuracy in many cases of interest. The use of modified distributions alleviates this problem, but analog computer experiments provide the most satisfactory attack for complicated situations and are easily instrumented.


Author(s):  
Денис Николаевич Соколов ◽  
Николай Юрьевич Сдобняков ◽  
Ксения Геннадьевна Савина ◽  
Андрей Юрьевич Колосов ◽  
Владимир Сергеевич Мясниченко

Описана архитектура и программное обеспечение Metropolis для проведения компьютерного моделирования методом Монте-Карло, а также его модификации. В качестве потенциала используется потенциал сильной связи, однако это не исключает возможности использования других модификаций апробированных многочастичных потенциалов. В сравнении с предыдущими программными реализациями метода Монте-Карло данная модификация увеличила скорость расчетов в 700 раз для выбранного размера наночастицы. Представлены данные по сходимости результатов моделирования методом Монте-Карло на примере температуры плавления. Разработанный программный комплекс постоянно апробируется для расчетов различных моно- и многокомпонентных наночастиц и наносистем. Полученные результаты показывают достаточно хорошее согласие с другими численными методами, в первую очередь с молекулярной динамикой, и реальным экспериментом. Дальнейшее развитие программного комплекса и улучшение показателей эффективности его работы планируется с использованием параллелизации вычислений и использование технологии вычислений на графических процессорах CUDA. The architecture and software Metropolis for computer simulation by the Monte Carlo method, as well as its modifications, are described. The tight-binding potential that does not exclude the possibility of using other modifications of many-body potentials. In comparison with previous software implementations of the Monte Carlo method, this modification has increased the rate of calculations by 700 times for a selected nanoparticle size. The data on the convergence of the results of modeling by the Monte Carlo method are presented on the example of the melting point. The developed software package is constantly tested for calculations of various mono- and multicomponent nanoparticles and nanosystems. The results obtained show fairly good agreement with other numerical methods, primarily molecular dynamics, and real experiment. Further development of the software package and its performance indicators are planned to be improved using parallelization of computations and the use of computing technology on graphics processors CUDA.


Author(s):  
R. W. Vook ◽  
R. Cook ◽  
R. Ziemer

During recent experiments on Au films, a qualitative correlation between hole formation and deposition rate was observed. These early studies were concerned with films 80 to 1000A thick deposited on glass at -185°C and annealed at 170°C. In the present studies this earlier work was made quantitative. Deposition rates varying between 5 and 700 A/min were used. The effects of deposition rate on hole density for two films 300 and 700A thick were investigated.Au was evaporated from an outgassed W filament located 10 cm from a glass microscope slide substrate and a quartz crystal film thickness monitor. A shutter separating the filament from the substrate and monitor made it possible to obtain a constant evaporation rate before initiating deposition. The pressure was reduced to less than 1 x 10-6 torr prior to cooling the substrate with liquid nitrogen. The substrate was cooled in 15 minutes during which the pressure continued to drop to the mid 10-7 torr range, where deposition was begun.


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