Geometry Specification for Band Structure Calculations
Before electronic band structure calculations can be done, the sequence of
atoms in the polymer must be supplied in a highly specific order. For a simple
polymer, the coordinates of all the atoms in the first fundamental unit cell
are given. These atoms can be in any order. The next set of atoms defined are
those for the next unit cell. These atoms must be in the same order as
the atoms in the first unit cell. For band structures at least two unit cells
must be defined. If more than two unit cells are defined, the atoms in the
other unit cells must be defined in the same order as those in the first unit
cell.
Because of the difficulty in generating data sets for band-structure work,
program BZ was written. Given a suitable data-set, BZ will generate a
MOPAC data set which can then be used for the calculation of band structures.