八面体
结晶学
晶体结构
粉末衍射
Atom(片上系统)
化学
X射线晶体学
衍射
材料科学
中子衍射
结构精修
单斜晶系
四方晶系
正交晶系
空间组
物理
嵌入式系统
光学
计算机科学
作者
J.R. Plaister,J.C. Jansen,R. A. G. de Graaff,D.J.W. IJdo
标识
DOI:10.1006/jssc.1995.1160
摘要
The crystal structure of Ca3HfSi2O9 has been determined from X-ray powder diffraction data using a recently developed software package in order to find individual intensities from overlapping reflections. The Hf atoms were found from the Patterson map, while Ca atoms were found in a subsequent heavy atom Fourier map. The other atoms were determined by trial and error using the Rietveld method. The atomic parameters for Ca3ZrSi2O9 were determined from neutron powder diffraction data with the structure of Ca3HfSi2O9 use as the trial model. Ca3HfSi2O9, a = 7.3517(4)Å, b = 10.1489(11) Å, c = 10.4319(12)Å, β = 91.(184(7)°, P21/c, and Z = 4; Ca3ZrSi2O9, a = 7.3603(1)Å, b = 10.1766(3) Å, c = 10.4514(3) Å, β = 90.875(2)°, P21/c, and Z = 4. The structure contains ribbons of edge-sharing octahedra parallel to [100]. The structure of these compounds is nearly the same as that of BeY2O4, substituting Si2O groups for 2 Be and doubling the a-axis. The mineral cuspidine (Ca4Si2O7(F,OH)2) has a very similar structure as well.
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