CELL445 Chapter Notes -Dan Shechtman, Cubic Crystal System, Identical Particles
6 Mar 2014
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Crystalline solids = solids with long range internal order. Particles are located at specific sites within the crystal. 2011 nobel prize in chemistry dan shechtman. Quasicrystals crystals with regular patterns (follow mathematical rules) but never repeat themselves. To describe the structure of crystals, we need 3d patterns. We use three sets of parallel planes called a lattice that will provide a 3d system for representing the position of particles (atoms, ions, molecules). A unit cell is the smallest portion of the crystal that when stacked together repeatedly without gaps can reproduce the entire crystal. Measurements of crystal structures are performed using x ray diffraction spectroscopy. The usual convention is to choose the one that indicates all of the symmetry present in the lattice (beyond the scope of this course). There are 7 systems and 14 types of unit cells that occur in nature.
