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The diffusion of a Ga atom on GaAs(001)beta 2(2 x 4): Local superbasin kinetic Monte Carlo

机译:Ga Atom对GaAs(001)β2(2×4)的扩散(2×4):局部超级止血素蒙特卡罗

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We use first-principles density-functional theory to characterize the binding sites and diffusion mechanisms for a Ga adatom on the GaAs(001)beta 2(2 x 4) surface. Diffusion in this system is a complex process involving eleven unique binding sites and sixteen different hops between neighboring binding sites. Among the binding sites, we can identify four different superbasins such that the motion between binding sites within a superbasin is much faster than hops exiting the superbasin. To describe diffusion, we use a recently developed local superbasin kinetic Monte Carlo (LSKMC) method, which accelerates a conventional kinetic Monte Carlo (KMC) simulation by describing the superbasins as absorbing Markov chains. We find that LSKMC is up to 4300 times faster than KMC for the conditions probed in this study. We characterize the distribution of exit times from the superbasins and find that these are sometimes, but not always, exponential and we characterize the conditions under which the superbasin exit-time distribution should be exponential. We demonstrate that LSKMC simulations assuming an exponential superbasin exit-time distribution yield the same diffusion coefficients as conventional KMC. Published by AIP Publishing.
机译:我们使用第一原理密度功能理论来表征GaAs(001)β2(2×4)表面上的Ga Adatom的结合位点和扩散机制。该系统中的扩散是一种复杂的过程,涉及11个独特的结合位点和相邻的结合位点之间的十六个不同的跳跃。在结合位点中,我们可以鉴定四种不同的超酶,使得超止吐蛋白内的结合位点之间的运动比离开超止吐蛋白的跳跃得多。为了描述扩散,我们使用最近开发的本地超方向动力学蒙特卡罗(LSKMC)方法,其通过描述Superbasins作为吸收马尔可夫链的超方案来加速传统的动力学蒙特卡罗(KMC)模拟。我们发现LSKMC比本研究探讨的条件速度快4300倍。我们的特征在于从超比酶中的出口时间分布,发现这些有时候,但并不总是,指数呈现,并且我们表征了超级空间出口时间分布应该是指数的条件。我们证明了假设指数超方素出口时间分布的LSKMC仿真产生与传统的kmc相同的扩散系数。通过AIP发布发布。

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