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A Linear Energy Stable Scheme for a Thin Film Model Without Slope Selection

机译:没有斜率选择的薄膜模型的线性能量稳定方案

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Abstract We present a linear numerical scheme for a model of epitaxial thin film growth without slope selection. The PDE, which is a nonlinear, fourth-order parabolic equation, is the L~2 gradient flow of the energy f_Ω((-2/1) ln(l + |▽φ|~2) + (2/∈2)|△φ(x)|~2)dx. The idea of convex-concave decomposition of the energy functional is applied, which results in a numerical scheme that is unconditionally energy stable, i.e., energy dissipative. The particular decomposition used here places the nonlinear term in the concave part of the energy, in contrast to a previous convexity splitting scheme. As a result, the numerical scheme is fully linear at each time step and unconditionally solvable. Collocation Fourier spectral differentiation is used in the spatial discretization, and the unconditional energy stability is established in the fully discrete setting using a detailed energy estimate. We present numerical simulation results for a sequence of ∈ values ranging from 0.02 to 0.1. In particular, the long time simulations show the - log(t) decay law for the energy and the t~(1/2) growth law for the surface roughness, in agreement with theoretical analysis and experimentalumerical observations in earlier works.
机译:摘要我们提出了一种不需选择斜率的外延薄膜生长模型的线性数值方案。 PDE是一个非线性的四阶抛物线方程,是能量f_Ω((-2/1)ln(l + |▽φ|〜2)+(2 /∈2)的L〜2梯度流。 |△φ(x)|〜2)dx。应用了能量函数的凸凹分解的想法,这导致了数值方案,该方案无条件地保持能量稳定,即耗能。与先前的凸度分裂方案相反,此处使用的特定分解将非线性项置于能量的凹面部分。结果,数值方案在每个时间步都是完全线性的,并且可以无条件求解。在空间离散化中使用了配置傅立叶频谱微分,并使用详细的能量估计在完全离散的环境中建立了无条件的能量稳定性。我们给出了一系列ε值从0.02到0.1的数值模拟结果。特别是,长时间的模拟表明,能量的-log(t)衰减定律和表面粗糙度的t〜(1/2)生长定律与早期工作中的理论分析和实验/数值观察一致。

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