Local 3D real space atomic structure of the simple icosahedral Ho11Mg15Zn74 quasicrystal from PDF data
Local 3D real space atomic structure of the simple icosahedral Ho11Mg15Zn74 quasicrystal from PDF data
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DOI：
10.1002/crat.200310131
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发表时间：
2003-01-01
影响因子：
1.5
通讯作者：
Assmus, W
中科院分区：
文献类型：
--
作者：
Br端hne, S;Uhrig, E;Assmus, W
我们提出了一种新的准晶结构确定的补充策略：利用内部x射线粉末衍射数据(MoKalpha(1)， Q（max) = 13.5Angstrom(-1)）的原子对分布函数（PDF），对简单的20面体（si） Ho11Mg15Zn74 [a(6D) = 5.144(3)Angstrom]在r = 17Angstrom的球内的局部原子结构进行了细化；R = 20.4%)。基本构件是一个105个原子的伯格曼簇{Ho8Mg12Zn85}。它的中心被一个Zn原子占据，而Ho9Mg26Zn65则是面心二十面体（fci）中的空洞。然后中心被另外12个Zn原子包围，形成一个二十面体（第一壳层）。第二层壳层由8个Ho原子组成，排列在立方体的顶点上，然后由12个Mg原子组成一个五边形十二面体，然后由12个Zn原子覆盖。第三个壳是一个变形的足球。60个Zn原子，反映了si相的Zn含量高于fci相。在我们的模型中，7%的原子位于星团之间。该模型对应于一个假设的二十面体(i)相的1/1近似。单原子的局部配位是非常扭曲的Frank-Kasper型，使人想起0/1-Mg2Zn11中存在的配位。(C) 2003 WILEY-VCH Verlag GmbH & Co., KGaA, Weinheim。
We present a new complementary strategy to quasicrystalline structure determination: The local atomic structure of simple icosahedral (si) Ho11Mg15Zn74 [a(6D) = 5.144(3)Angstrom] in a sphere of up to r = 17Angstrom was refined using the atomic pair distribution function (PDF) from in-house X-ray powder diffraction data (MoKalpha(1), Q(max) = 13.5Angstrom(-1); R = 20.4%). The basic building block is a 105-atom Bergman-Cluster {Ho8Mg12Zn85}. Its center is occupied by a Zn atom - in contrast to a void in face centred icosahedral (fci) Ho9Mg26Zn65. The center is then surrounded by another 12 Zn atoms, forming an icosahedron (1st shell). The 2nd shell is made up of 8 Ho atoms arranged on the vertices of a cube which in turn is completed to a pentagon dodecahedron by 12 Mg atoms, the dodecahedron then being capped by 12 Zn atoms. The 3rd shell is a distorted soccer ball. of 60 Zn atoms, reflecting the higher Zn content of the si phase compared to the fci phase. In our model, 7% of all atoms are situated in between the clusters. The model corresponds to a hypothetical 1/1-approximant of the icosahedral (i) phase. The local coordinations of the single atoms are of a much distorted Frank-Kasper type and call to mind those present in 0/1-Mg2Zn11. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.