Coordination number of 3D close packing


As @Poutnik said, the packing is infinite, so there are no corner spheres.

Consider it this way-

  1. Each sphere is in contact with four other spheres in it's own layer, as shown- enter image description here
  1. 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 co-ordination number is 4+2=6.

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Updated on February 01, 2023


  • RealGuru
    RealGuru 9 months

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

    3D close packing from 2-D square close packed layers

    • Poutnik
      Poutnik over 2 years
      The 3D packing is considered infinite, so there is no corner sphere.
  • Raghavendra Singh
    Raghavendra Singh over 2 years
    Please note that spheres diagonal to each other are NOT considered adjacent. Also, we have only taken into account Cubic close packing here...