Coordination number of 3D close packing
1,241
As @Poutnik said, the packing is infinite, so there are no corner spheres.
Consider it this way
 Also note that each sphere is in contact with one sphere on the layer just above it and one sphere on the layer just below it. A total of two additional spheres thus.
Hence the coordination number is 4+2=6.
Author by
RealGuru
Updated on February 01, 2023Comments

RealGuru 4 months
Can anyone explain me that how the coordination number of corner sphere of this 3D packing is 6 ? it should be 3

Poutnik about 2 yearsThe 3D packing is considered infinite, so there is no corner sphere.


Raghavendra Singh about 2 yearsPlease note that spheres diagonal to each other are NOT considered adjacent. Also, we have only taken into account Cubic close packing here...