# About coordination number

Quote from YuCheng Xue on May 30, 2020, 4:08 amDear ovito experts!

I'm doing a simulation of particles hitting a workpiece, the material of the work piece is aluminum. In the initial state, I used ovito's "expresstion select" function to analyze, the atomic coordination number of the upper and lower surfaces of the workpiece is 8, and the remaining atomic coordination number is 12. After the collision, I continued to analyze the coordination number of the atoms, but I found that there were few atoms with the coordination number greater than 12, and there were surprisingly many atoms with the coordination number equal to 11.But I think the correct situation should be: after the end of the abrasive particle impact, the number of atoms with a coordination number greater than 12 should increase greatly. Why would atoms with a coordination number less than 12 increase more than atoms with a coordination number greater than 12?Figure 1 is a coloring picture I made based on the coordination number.(Atoms with coordination numbers 8 and 12 have been deleted)Hope for your help!Yours sincerely!Yucheng Xue

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Quote from Constanze Kalcher on June 3, 2020, 1:04 pmDear YuCheng,

I'm not sure I understand your question correctly. Please note that the Coordination Number that is returned by the Coordination Analysis modifier gives you the number of neighboring atoms found in the specified cutoff range.

Did you mean to count the next-nearest neighbors only? In that case I would suggest you to try and use the Voronoi Analysis modifier instead to compute the Coordination Number.

- Constanze

Dear YuCheng,

I'm not sure I understand your question correctly. Please note that the Coordination Number that is returned by the Coordination Analysis modifier gives you the number of neighboring atoms found in the specified cutoff range.

Did you mean to count the next-nearest neighbors only? In that case I would suggest you to try and use the Voronoi Analysis modifier instead to compute the Coordination Number.

- Constanze