Geometries are defined in terms of the atoms involved and their coordinates.
If you are new to MOPAC, then the fastest way to understand the general layout
is to look at an example of a simple data set.

The data is in a "free-format" This means that integers and real numbers can be interspersed, and numbers can be separated by one or more spaces, a tab and/or by one comma. If a number is not specified, its value is set to zero.

The geometry can be defined in terms of either internal or Cartesian coordinates, or a mixture of the two, or Gaussian format.

- Definition of Elements for MNDO, AM1, PM3, RM1, PM6, and PM7
- Definition of Isotopes
- Atom labels
- Internal Coordinate Definition
- Cartesian Coordinate Definition
- Mixed Cartesian and internal coordinate definition
- Translation Vector
- Optimization flags
- Applying constraints, freezing coordinates, and fixing distances, etc.
- Specification of Protein Data Bank (PDB) geometries
- Specification of Gaussian Z-matrices
- Specification of TURBOMOLE geometries
- Conversion Between Various Formats
- Notes on proteins
- Multiple structures in one job