10. Solids

Quan­tum me­chan­ics is es­sen­tial to make sense out of the prop­er­ties of solids. Some of the most im­por­tant prop­er­ties of solids were al­ready dis­cussed in chap­ter 6. It is a good idea to re­view these sec­tions be­fore read­ing this chap­ter.

The dis­cus­sion will re­main re­stricted to solids that have a crys­tal struc­ture. In a crys­tal the atoms are packed to­gether in a reg­u­lar man­ner. Some im­por­tant ma­te­ri­als, like glass and plas­tic, are amor­phous, they do not have such a reg­u­lar crys­tal struc­ture, and nei­ther do liq­uids, so not all the ideas will ap­ply to them.