دانلود رایگان مقاله انگلیسی محاسبات عددی بهره وری بالا برای مدلسازی دینامیک گاز بر اساس DFT و تقریب - IEEE 2018

Abstract

In article questions of high productivity numerical computations for gas dynamics modelling based on discrete Fourier transform and approximation are considered. The offered method is based on use of piecewise and analytical approximation of the equations of dynamics of gas and application of discrete transformations of Fourier. It allows to increase the accuracy of calculations and to increase the speed of convergence of the solution of the equations in space of three dimensions and in time. The iterative scheme of calculations is offered. Speed of convergence and an error of approximation is estimated. The possibility of approximation is considered by various approximating kernels. The computing algorithm was developed for fast calculation of a stream of gas and heat conductivity in the reactor of a vapor-phase epitaxy for crystal growth on computing systems of small productivity.

VII. CONCLUSIONS

An essential problem in the preparation of Group III nitrides is the absence of nitride substrates that are most suitable for the parameters of the crystal lattice and the coefficient of thermal expansion for the growth of GaN structures, because large bulk GaN single crystals can not be grown by conventional methods. Because of the high melting point of GaN (~ 2500 ° C) and the high equilibrium nitrogen pressure above the melt, a sufficiently low decomposition temperature of GaN (~ 1000 ° C), it is impossible to grow a large single GaN single crystal by standard methods and then cut it into substrates. Therefore, the main method for growing heterostructures based on III-N compounds is epitaxy from organometallic compounds. As an alternative to GaN substrates for the growth of nitride structures, sapphire and 6H-SiC crystals are widely used. However, neither sapphire nor SiC prevents the epitaxial growth of GaN without the use of special techniques for the nucleation of III-N crystals on them. These methods are empirical in nature, and there are few published studies on the relationship between growth conditions and the formation of nitride layers.

To some extent, this is due to the lack of attention to the processes occurring in the reactor with the growth of the VPthe relationship between the rate of decomposition and the synthesis of nitrides, their dependence on the already-grown growth conditions of the MOVPE method.

An understanding of the nature of the epitaxial process leads to an understanding of the processes of formation of epitaxial layers on foreign substrates and there is a conscious management of growth conditions to achieve the necessary characteristics of the growing layers. Therefore, the aim of this paper is to simulate the main processes that determine the quality and rate of growth of structures in the reactor.