arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2012.15133math.NAcs.NA
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方相场晶体方程的二阶精确标量辅助变量(SAV)数值方法

A second order accurate scalar auxiliary variable (SAV) numerical method for the square phase field crystal equation

Min Wang, Qiumei Huang, Cheng Wang

摘要:

在本文中,我们提出并分析了一个二阶精度(在时间上)的数值方相场晶体(SPFC)方程,梯度流模拟晶体动力学在原子尺度上的空间,但在时间上的扩散尺度。它与标准相场晶体模型的主要区别是在自由能势中引入了4-拉普拉斯项,这反过来又导致了更高程度的非线性。为了在保持非线性能量稳定性的同时使数值格式线性化,我们使用标量辅助变量(SAV)方法,其中在时间模板中应用二阶向后微分公式(BDF)。同时,由于涉及到4-Laplacian项,结合非线性能量泛函的下界的推导,直接应用SAV方法面临一定的困难。在所提出的数值方法中,对物理能量泛函进行了适当的分解,使得非线性能量部分具有一个良好的全局下界,而其余项则为具有正特征值的常系数扩散项.反过来,数值方案可以非常有效地实现恒定系数泊松型求解器(通过FFT),并通过引入辅助变量建立能量稳定性,并提供了建议SAV方法的最佳速率收敛分析。最后给出了几个数值实验,实验结果表明了该格式的有效性和准确性。

英文摘要:

In this paper we propose and analyze a second order accurate (in time) numerical scheme for the square phase field crystal (SPFC) equation, a gradient flow modeling crystal dynamics at the atomic scale in space but on diffusive scales in time. Its primary difference with the standard phase field crystal model is an introduction of the 4-Laplacian term in the free energy potential, which in turn leads to a much higher degree of nonlinearity. To make the numerical scheme linear while preserving the nonlinear energy stability, we make use of the scalar auxiliary variable (SAV) approach, in which a second order backward differentiation formula (BDF) is applied in the temporal stencil. Meanwhile, a direct application of the SAV method faces certain difficulties, due to the involvement of the 4-Laplacian term, combined with a derivation of the lower bound of the nonlinear energy functional. In the proposed numerical method, an appropriate decomposition for the physical energy functional is formulated, so that the nonlinear energy part has a well-established global lower bound, and the rest terms lead to constant-coefficient diffusion terms with positive eigenvalues. In turn, the numerical scheme could be very efficiently implemented by constant-coefficient Poisson-like type solvers (via FFT), and energy stability is established by introducing an auxiliary variable, and an optimal rate convergence analysis is provided for the proposed SAV method. A few numerical experiments are also presented, which confirm the efficiency and accuracy of the proposed scheme.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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