Ionic and Covalent Solids - Structures

As we noted in our discussion of metal and alloy structures in Chapter 6, there is an intimate connection between the structures and the physical properties of materials. As we "graduate" from simple metal structures based on sphere packings to more complex structures, we find that this is still true. In this chapter we will try to systematize the structures of inorganic solids - metal oxides, halides, sulfides, and related compounds - and develop some rules for which structures to expect based on electronegativity differences, hard-soft acid-base rules, and other periodic trends. We will see that many of these structures are related to the sphere packings that we learned about in Chapter 6.

Learning goals for Chapter 8:

• Describe many crystal structures in terms of close-packed frameworks with systematic filling of octahedral and tetrahedral holes.
• Represent crystal structures by drawing them in sections.
• Rationalize, using chemical principles, why certain crystal structures are stable for certain compounds but not for others, as well as why certain structural and bonding motifs are preferred for certain compounds relative to others.
• Predict which crystal structures are most favorable for a given composition based on ionicity and periodic trends.
• Explain structure-dependent properties such as ferroelectricity and magnetic ordering based on crystal structures.
• Understand intercalation reactions in layered and open framework solids.
• Predict the preferred formation of normal or inverse spinels using arguments from transition metal chemistry (e.g. crystal field stabilization energies).

Inorganic solids often have simple crystal structures, and some of these structures are adopted by large families of ionic or covalent compounds. Examples of the most common structures include NaCl, CsCl, NiAs, zincblende, wurtzite, fluorite, perovskite, rutile, and spinel. We will develop these structures systematically from the close packed and non-close packed lattices shown below. Some layered structures, such as CdCl₂ and CdI₂, can be thought of as relatives of simple ionic lattices with some atoms "missing."

• 

  Face-centered cubic (fcc) or cubic close-packed (ccp)
 
• 

  Hexagonal close-packed (hcp)
 
• 

  Body-centered cubic
 
• 

  Simple cubic

 To continue reading click on the link below:

https://en.wikibooks.org/wiki/Introduction_to_Inorganic_Chemistry/Ionic_and_Covalent_Solids_-_Structures