Crystal Structures: Properties Of Materials Can Be Predicted
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. For example, two forms of carbon have different properties to the extreme. Even though graphite and diamond are both composed of only carbon atoms, the properties could not be more different.
In graphite, the structure has tight hexagonal layers that are relatively distant from each other. When the tip of a pencil is dragged across a page of paper, layers of graphite are deposited to make lines.
The diamond structure has tetrahedral bonded carbon atoms, where each atom is connected to four other atoms with relatively short distance between the atoms. This is a cubic face-centered structure and one of the hardest substances on earth. Yet, both are comprised of nothing other than carbon atoms.
The study of crystal structure starts with the unit cell. Unit cells are arranged along three axis to form the material. For classification purposes, we find the 14 Bravais lattices most useful to define the various geometric arrangements of atoms. Amazingly, all substances can be defined by their lattice structure. They are similar to, but not quite the same as, the seven crystal systems.
Disciplines that explore crystallography include Geology, Earth Science, Chemistry, Material Science and others. Since 1975, Klinger Educational has offered over 300 permanently assembled models, formal lattices (i.e. CFC, CBC, HCP), Miller indices, teaching sets (i.e. basic set of 9 Structures and 14 Bravais type lattices or space lattices) as well as orbitals.
The value of Klinger’s three dimensional models is that they are robust structures, able to be handled to observe the axis and geometric system exhibited by the material. Dislocation structures are particularly difficult to visualize, so Klinger offers an edge and a screw dislocation model with the normal matrix in one color and the distorted atoms in a contrasting color.
The Miller Indices models exhibit the different planes using color coded balls to display the (100) (110) (111) (120) (320) (210) planes, though not all in one structure. Below is one of the available models.
Orbital models are designed to represent the angular distribution of the ‘s’, ‘p’, ‘d’ and ‘f’ orbitals to illustrate several aspects of Molecular Orbital and Crystal field Theory. Models are constructed of painted, hard wood lobes mounted on nickel plated steel axes. Each model is mounted and labeled; available individually or as sets.
The study of crystal structure in inorganic materials yields much knowledge of a world we live in yet will never observe with our naked eye.