Name: Radius Ratio and Coordination Number
Uploaded: 2019-07-19
Duration: 3 min 49 s
Description: The radius ratio plays a very important role in the determination of a structure in an ionic crystal. Watch the video to know more about the radius ratio of...

Question

Explain with the help of diagrams of structural differences between three types of cubic crystals.

Accepted Answer

Primitive /Simple unit cell: This unit cell consists of one lattice point on each corner of the cube. Each atom at a lattice point is then shared equally between eight adjacent cubes, and the unit cell therefore contains in total one atom.

Found in all crystal systems.

Body centred unit cell : This unit cell has one lattice point in the centre of the unit cell in addition to the eight corner points. It has a net total of two lattice points per unit cell.

Found only in Cubic, Tetragonal, Orthorhombic and Monoclinic systems.

Face centred unit cell : It has lattice points on the faces of the cube, that each gives exactly one half contribution, in addition to the corner lattice points, giving a total of four atoms per unit cell.

Found only in cubic and orthorhombic systems. The face-centred cubic system is closely related to the hexagonal close packing $(hcp)$ system, where two systems differ only in the relative placements of their hexagonal layers.

Explain with the help of diagrams of structural differences between three types of cubic crystals.

Important Questions on States of Matter: Solid State

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