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Posted on 20th Nov 2021 04:46:10 in
Question 1.7) How will you distinguish between the following pairs of terms:
(i) Hexagonal close-packing and cubic close-packing?
(ii) Crystal lattice and unit cell?
(iii) Tetrahedral void and octahedral void?
Answer :
(a) Cubic close packing:-
When a third layer is placed over the second layer in a manner that the octahedral voids are covered by the spheres, a layer different from the first
(A) and second
(B) is obtained.
If we continue packing in this manner we get the cubic close packing.Hexagonal close packing: When the third layer is placed over the second layer in a way that the tetrahedral voids are covered by the spheres, a 3D close packing is produced where spheres in each third or alternate layers are vertically aligned. If we continue packing in this order we get hexagonal close packing.
(b) Unit cell:-
It is the smallest 3D dimensional portion of a complete space lattice, which when repeated over and over again in different directions from the crystal lattice.
Crystal lattice :-
it is a regular orientation of particles of a crystal in a 3D space.
(c) Octahedral void :-
it is a void surrounded by 6 spheres.
Tetrahedral void :-
it is a void surrounded by 4 spheres.
