Question

What is the purpose of stererographic Projection in crystallography in easy words and the ways to find stereographic projection in a cubic crystal.

Answer 1

Stereographic projection is a method used in crystallography and structural geology to depict the angualar relationship between crystal faces and geologic structures. The tool when investigating atomic planes or directions and visualization various orientaion dependent phenomenon.In streographic projection crystal direction are projected onto a plane.

For finding stereographic projection in a cubic crystal in the following ways:-

The cubical structure is oriented so, that xy plane lies in the horizontal plane.The solid green cirles represent the plane whose normals project into the upper hemisphere, while the open red circle represents the planes whose normal project into the lower hemisphere.The normals to four vertical faces of the cubic structure (100),(010),(-100) and (0-10),are horizontal and thus intersect the sphere at the equator.Therefore,all the verticle planes have poles on the equtorial circle , so called theprimitive circle.The normal to the bottom face,(00-1),projects at the centre (green open circle).