graphite lattice model

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This text describes three types of elemental carbon models - "Buckyballs," "Nanotubes," and a "Diamond Lattice Model." Graphite, the most common form of carbon, is yet to be discussed. The Naval Research Laboratory crystal site provides information about graphite's three forms with available coordinates and rotatable models for viewing using a javascript applet; however, the site seems discontinued and has been replaced by "Carbon and Related Structures" at a new link. The A9 hexagonal form of graphite is the easiest to print, as it can be calculated with pencil and paper for accurate positioning. It consists of planar sheets of carbon atoms in a hexagonal array with a bond distance of 1.42 Angstroms. The intermediate layer is positioned at a distance of 3.35 Angstroms from the upper and lower layers, forming an identical hexagonal array. A Fortran program named "expand_graphite.f" creates the model using simple geometry and outputs openSCAD module calls. Two models are provided: Graphite7_x4_2c.stl, a sturdy version with atoms, and Graphite11_x4_2c.stl, an open model without atoms showing only the hexagonal lattice. The former takes about 90 minutes to print with a raft, while the latter prints in just over an hour but is fragile.