How will you distinguish between the following pair of terms :
(i) hexagonal close-packing and cubic close-packing?
(ii) crystal lattice and unit cell ?
(iii) tetrahedral void and octahedral void?
How will you distinguish between the following pair of terms :
(i) hexagonal close-packing and cubic close-packing?
(ii) crystal lattice and unit cell ?
(iii) tetrahedral void and octahedral void?
In hexagonal close packing (hcp), the spheres of the third layer are vertically above the spheres of the first layer. It means tetrahedral voids of the second layer are covered by the spheres of the third layer. The AB AB AB..... type.
In cubic close packing (ccp), the spheres of third layer cover the octahedral voids of second layer. But the spheres of the fourth
layers are aligned with those of the first layer. The pattern is ABC ABC...... type.
(ii) Crystal lattice is the three dimensional arrangement of identical point in the space which represent how the constituent particles (atoms, ions, molecules) are arranged in a crystal.
Unit cell is the smallest portion of a crystal lattice which, when repeated in different directions, generates the entire lattice.
(iii) Tetrahedral voids are surrounded by four spheres which lie at the vertices of a regular tetrahedron. There are 2 tetrahedral voids per atom in a crystal. Octahedral voids are surrounded by six spheres and formed by a combination of two triangular voids of the first and second layer. There is one octahedral void per atom in a crystal.
In hexagonal close packing (hcp), the spheres of the third layer are vertically above the spheres of the first layer. It means tetrahedral voids of the second layer are covered by the spheres of the third layer. The AB AB AB..... type.
In cubic close packing (ccp), the spheres of third layer cover the octahedral voids of second layer. But the spheres of the fourth
layers are aligned with those of the first layer. The pattern is ABC ABC...... type.
(ii) Crystal lattice is the three dimensional arrangement of identical point in the space which represent how the constituent particles (atoms, ions, molecules) are arranged in a crystal.
Unit cell is the smallest portion of a crystal lattice which, when repeated in different directions, generates the entire lattice.
(iii) Tetrahedral voids are surrounded by four spheres which lie at the vertices of a regular tetrahedron. There are 2 tetrahedral voids per atom in a crystal. Octahedral voids are surrounded by six spheres and formed by a combination of two triangular voids of the first and second layer. There is one octahedral void per atom in a crystal.
