MIT 3.60 Lec 11a Symmetry, Structure, Tensor Properties of Materials
PROFESSOR: We are thundering rapidly to the midpoint of the term. I think a week from this coming Thursday will be exactly halfway, and the halfway point is when I usually try, give or take a day, to change gears very abruptly and start looking at the symmetry of physical properties and tensors and actual discussion of physical properties that are anisotropic. So we'll be finishing up our discussion of symmetry fairly quickly. We still have, however, some major derivations to perform, and we'll get into one of these today. Last time we had begun the process of deriving what are called the point groups as opposed to the plane groups. The plane groups were combinations of symmetry with a lattice that extended throughout a plane in space. A point group we've seen in the form of two-dimensional point groups. We're now going to today derive the three-dimensional point groups. And, again, the name stems from the fact that these are clusters of symmetry about a c...