Epitaxial growth of ordered and disordered granular sphere packings.
Epitaxial growth of ordered and disordered granular sphere packings.
复制标题
DOI：
10.1103/physreve.90.032203
复制
发表时间：
2014-09
期刊：
影响因子：
--
通讯作者：
Andreea Panaitescu;A. Kudrolli
中科院分区：
文献类型：
--
作者：
Andreea Panaitescu;A. Kudrolli
我们表明，外延可以用来获得一个广泛的有序无序的颗粒堆积通过简单地改变沉积流量。我们证明了无缺陷的面心立方（fcc）单晶可以通过在重力场中将无热颗粒球随机沉积到具有模板表面的容器中而无需直接操作来获得。该填充对应于最大球体填充分数，并且当基板对应于面心立方晶体的（100）平面被模板化并且容器侧是球体直径的整数倍时获得。我们发现，当沉积的颗粒一次一个地静止而不损坏基底时，就会获得最大的球体堆积。当通量增加时，观察到向无序堆积的过渡。使用微X射线计算机断层扫描，我们发现，缺陷成核在容器中的填料生长的颗粒合作的边界来休息以上的本地潜在的最小值。这导致从有序到无序的松散堆积的过渡，其以倒锥形的形式生长，顶点位于缺陷成核位点。我们捕捉观察到的减少，以便使用一个最小的模型，其中一个缺陷导致生长的进一步缺陷在相邻的网站上的层与概率增加的沉积通量。
We demonstrate that epitaxy can be used to obtain a wide range of ordered to disordered granular packings by simply changing the deposition flux. We show that a defect-free face-centered-cubic (fcc) monocrystal can be obtained by depositing athermal granular spheres randomly into a container with a templated surface in a gravitational field without direct manipulation. This packing corresponds to the maximum sphere packing fraction and is obtained when the substrate is templated corresponding to the (100) plane of a fcc crystal and the container side is an integer multiple of the sphere diameter. We find that the maximum sphere packing is obtained when the deposited grains come to rest, one at a time, without damaging the substrate. A transition to a disordered packing is observed when the flux is increased. Using micro x-ray computed tomography, we find that defects nucleate at the boundaries of the container in which the packing is grown as grains cooperatively come to rest above their local potential minimum. This leads to a transition from ordered to disordered loose packings that grow in the form of an inverted cone, with the apex located at the defect nucleation site. We capture the observed decrease in order using a minimal model in which a defect leads to growth of further defects in the neighboring sites in the layer above with a probability that increases with the deposition flux.