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How can i find the coordination number in this case

How can i find the coordination number in this case

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Grade:12th pass

2 Answers

Sujit Kumar
111 Points
5 years ago
I’m calling atoms, spheres...
The spheres are touching along the edges
All the spheres are of equal radius.
Therefore edge of cube is 4r, where r is the radius of a sphere.
     Taking    One    Face
Radius of the face-centered sphere is r
Length of diagonal is r(20.5)              ….....(radius * root 2)
Therefore for the face-centered sphere to touch the spheres at the corners.... radius of  the face-centered sphere should be r(20.5-2) which is greater than r.
Hence the face-centered sphere will only touch the edge centered spheres and not the corner sphere.
The face-centered sphere cannot touch any other sphere.
 
Hence the face-centered sphere only touches 4 edge-centered spheres.
Hence CN (Coordination Number)=4
Sujit Kumar
111 Points
5 years ago
The above case is the CN for an atom on a face center
For for atom B
It will touch 2 corner atoms (one to the left of it and another to the right) and
It will touch 4 face centered atoms (one on top, another forward.... Another on another unit cell bottom and a final on another unit cell backward)
So the CN will be 6

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