# Explain how no of tetrahedral void s is calculated actually the reason of doubt is that I am getting 16 as answer instead if eight

Umakant biswal
5349 Points
8 years ago
@ harman ,
tetrahedral voids are actually the false voids and octahedral voids are the true voids ,
In cubic close packed structure, spheres of the second layer lie above the triangular voids of the first layer. Each sphere touches the three spheres of the first layer. By joining the centre of these four spheres, it forms a tetrahedron and the empty space left over by joining the centre of these spheres forms a tetrahedral void.

In closed packed structure the number of tetrahedral voids is two times the number of spheres.

Let the number of spheres be n.

Then the number of tetrahedral voids will be 2n.
THEN U HAVE TO CALCULATE ACCORDING TO THE PACKING ARRENGEMENT .
FOR EXAMPLE FOR CCP THE TETRAHEDRAL VOIDS WILL BE 8,,
AND FOR HCP IT WILL BE AROUND 12 ,,,
and i donot think it will be 16 in the case of ccp .
KINDLY POST THAT QUESTION AGAIN ,

ALL THE BEST ..

Umakant biswal
5349 Points
8 years ago
@ harman
what u have to understand by tetrahedral void is that sphere of second layer will allign with the tringular voids of first layer , and by joining the corner , u will get a regular tetrahedral structure , so, its called as tetrahedral void .
the no of tetrahedral void is actually 2 times the no of spheres participated for the packing process ,
that means the number will be 2n .
EXAMPLE- FOR CCP , THE NO OF SPHERE PARTICIPATED IN PACKING = 4
SO, THE NO OF TETRAHEDRAL VOID = 4*2 =8
THE OCTAHEDRAL VOID WILL BE 4 IN THAT CASE ,
AND in case of hcp structure it will be 12 no of tetrahedral voids , and 6 no of octahedral voids .
KINDLY COME BACK WITH THE QUESTION IN WHICH U GOT 16 AS THE ANSWER , THE QUES MIGHT BE DIFFRENT LIKE ADDING SOME ATOMS IN DIAGONAL ,