> They are not 100% frozen in a 100% perfect lattice structure. They still move a little around the positions where they "should" be. Something similar happens

> They are not 100% frozen in a 100% perfect lattice structure. They still move a little around the positions where they "should" be. Something similar happens with atoms in a normal crystal. Thanks for the explanation. In retrospect this seems like it should be obvious (at least for some definition of obvious); I was probably reading a little too hard.