Pt/Al（111）中的自组织瞬态易化原子输运
Self-organized transient facilitated atomic transport in Pt/Al(111)
摘要：
在主体材料中的原子输运过程中，杂质原子需要克服由热力学偏压或在超低温下由量子隧穿驱动的能垒。在这篇文章中，我们使用原子模拟证明，在超低温下，当Pt/Al（111）杂质/主体系统自发地自组织成混合配置时，在没有隧穿的情况下，层间原子瞬态输运也是可能的。在超低温下，还没有报道过如此快速的无热协同过程。所概述的新的瞬态原子交换机制可能具有普遍的有效性。我们发现，尽管Pt/Al的动态势垒高度很低，但超低温重粒子势垒穿越的来源是本征的，原子混合和表面合金化不需要外加偏压。该机制是由Al（111）表面的局部热化驱动的，在没有任何外部刺激的情况下，系统自发地以自组织的方式排列。短寿命热化区的核心达到局部温度$\sim 1000$ K（包括几十个Al原子），而模拟电池的平均温度为$\sim 3$ K。瞬态促进混合过程也发生排斥杂质-主机的相互作用势，导致负的原子迁移率，因此原子注入在很大程度上是独立的杂质-表面相互作用的强度。我们预测，类似的奇异行为在其他材料中也是可能的。
英文摘要：
During the course of atomic transport in a host material, impurity atoms need to surmount an energy barrier driven by thermodynamic bias or at ultra-low temperatures by quantum tunneling. In the present article we demonstrate using atomistic simulations that at ultra-low temperature transient inter-layer atomic transport is also possible without tunneling when the Pt/Al(111) impurity/host system self-organizes itself spontaneously into an intermixed configuration. No such extremely fast athermal concerted process has been reported before at ultra low temperatures. The outlined novel transient atomic exchange mechanism could be of general validity. We find that the source of ultra-low temperature heavy particle barrier crossing is intrinsic and no external bias is necessary for atomic intermixing and surface alloying in Pt/Al although the dynamic barrier height is few eV. The mechanism is driven by the local thermalization of the Al(111) surface in a self-organized manner arranged spontaneously by the system without any external stimulus. The core of the short lived thermalized region reaches the local temperature of $\sim 1000$ K (including few tens of Al atoms) while the average temperature of the simulation cell is $\sim 3$ K. The transient facilitated intermixing process also takes place with repulsive impurity-host interaction potential leading to negative atomic mobility hence the atomic injection is largely independent of the strength of the impurity-surface interaction. We predict that similar exotic behaviour is possible in other materials as well.
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