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arXiv 1306.5171cond-mat.soft
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受限于表面的二元磁流体的Spinodal分解

Spinodal decomposition of a binary magnetic fluid confined to a surface

Ken Lichtner, Sabine H. L. Klapp

摘要:

在我们以前的工作[J. Chem. Phys. \textbf{136},024502(2012)]中,我们报道了由磁性物质的铁磁相互作用驱动的二维二元海森堡流体混合物的分层相变。在这里,我们提出了一个理论研究的\textit{time-dependent}粗化发生在两相区域内的密度-浓度平面,也被称为spinodal分解。我们的研究是基于动力学密度泛函理论(DDFT)。混合物中的粒子被建模为二维表面上的高斯软球,其中一个组件携带海森堡类型的经典自旋。为了研究两相区,我们首先提出了一个线性稳定性分析,相对于小,谐波密度扰动。其次,为了捕捉非线性效应,我们将DDFT与Percus的测试粒子方法相结合来计算时间相关的结构因子。对于平均畴尺寸$l$在调幅分解过程中随时间$t$的增长,我们观察到一个幂律行为$l\propto t^{δ_α}$与$δ_m\simeq 0.333$的磁性物种和$δ_n\simeq 0.323$的非磁性物种。

英文摘要:

In our previous work [J. Chem. Phys. \textbf{136}, 024502 (2012)], we reported a demixing phase transition of a two-dimensional, binary Heisenberg fluid mixture driven by the ferromagnetic interactions of the magnetic species. Here, we present a theoretical study for the \textit{time-dependent} coarsening occuring within the two-phase region in the density-concentration plane, also known as spinodal decomposition. Our investigations are based on Dynamical Density Functional Theory (DDFT). The particles in the mixture are modelled as Gaussian soft spheres on a two-dimensional surface, where one component carries a classical spin of Heisenberg type. To investigate the two-phase region, we first present a linear stability analysis with respect to small, harmonic density perturbations. Second, to capture non-linear effects, we calculate time-dependent structure factors by combining DDFT with Percus' test particle method. For the growth of the average domain size $l$ during spinodal decomposition with time $t$, we observe a power-law behavior $l\propto t^{δ_α}$ with $δ_m\simeq 0.333$ for the magnetic species and $δ_n\simeq 0.323$ for the non-magnetic species.

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