Conversion Between Various Formats

MOPAC can accept any of the following formats: Cartesian, MOPAC internal coordinates, a mixture of Cartesian and MOPAC internal coordinates,  and Gaussian internal coordinates. Both MOPAC and Gaussian Z-matrices can also contain dummy atoms. If the 0SCF option is requested, the geometry defined on input will be printed in MOPAC Z-matrix format, along with other optional formats.

The type(s) of geometry printed at the end of a 0SCF calculation depend only on the keywords XYZ, INT, AIGOUT,  and NOXYZ. The geometry printed is independent of the type of input geometry, and therefore makes a convenient conversion mechanism.

If XYZ is present, all dummy atoms are removed and the internal coordinate definition remade. All symmetry relations are lost if XYZ is used.

If NOXYZ is present, Cartesian coordinates will not be printed. If AIGOUT is present, a data set using Gaussian Z-matrix format is printed.

Note: Only if the keyword SYMMETRY is present in a MOPAC internal coordinate geometry, or two or more internal coordinates in a Gaussian Z-matrix have the same symbolic will symmetry be present in the MOPAC or Gaussian geometries output.