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The Model for Polonium Crystal Structure

Skills to develop

The Model for Polonium Crystal Structure

If you always consider atoms to be spherical, you certainly will consider the a simple cubic structure very unstable. The unit cell of such a structure is cubic, and the origin can be the center of an atom. One such sphere is place in the diagram here, and you may complete the diagram by placing 7 more spheres at the 7 corners.

We don't encounter simple cubic structure with one atom per unit cell often. However, one phase of polonium called alpha polonium has been reported to have such a structure by Beamer and Maxwell in 1946, and they re-affirm the result in 1949.

This so called primitive or simple cubic structure in the packing of spheres contains only one atom per cubic unit. Don't take these word for granted, work it out yourself from the diagram shown here or one you have completed.

Since correlating atomic radius with unit cell edge of this structure is simple, we use it as a model of teaching. We ask you to calculate some relevant crystal parameters of this model.

Example 1

The alpha polonium is primitive cubic with the cell edge of 335 pm. Show the following:

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