What are the structures of potassium superoxide and xenon hexafluoride? [closed]








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I have 2 questions in mind:


1) What is the structure of the superoxides? More specifically, what is the structure of $\ce{KO\_2}$?


2) What is the structure of and dipole moment for $\ce{XeF\_6}$?




[Xenon hexafluoride](https://en.wikipedia.org/wiki/Xenon_hexafluoride)'s geometry is not easy to be described but it is assumed to be in $C\_{3v}$-symmetry - not octahedral! - in gas phase which is supported by electron diffraction measurements and quantum chemical calculations. It crystallizes in at least six to seven different known structures. [1]


As it is further written



> 
> Konrad Seppelt, an authority on noble gas and fluorine chemistry, says, "the structure is best described in terms of a mobile electron pair that moves over the faces and edges of the octahedron and thus distorts it in a dynamic manner."
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On you question regarding the dipole moment - for the $C\_{3v}$-symmetry $\ce{XeF6}$ the dipole moment is calculated to be $0.46~\mathrm{D}$. [2]


The structure of $\ce{KO2}$ can also be found on [wikipedia](https://en.wikipedia.org/wiki/Potassium_superoxide). There you find the following picture, showing it in it's body-centered cubic unit cell.


![unit cell of potassium superoxide](https://i.stack.imgur.com/fQ8rh.png)


[1] [S. Hoyer, T. Emmler, K. Seppelt, *J. Fluor. Chem.* **2006**, *127 (10)*, 1415-1422](http://dx.doi.org/10.1016/j.jfluchem.2006.04.014)


[2] [T. D. Crawford, K. W. Springer, H. F. Schaefer III *J. Chem. Phys.* **1995**, *102 (8)*, 3307-3311](http://www.crawford.chem.vt.edu/PDF/JChemPhys_102_3307.pdf)


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