When SURVEY is present, PARAM will run the supplied set of MOPAC reference data files, but, instead of optimizing parameters, a comparison of the calculated and reference data sets will be generated. The normal mode of operation is for each geometry to be optimized, then the calculated quantities and reference quantities printed to files. In addition to the <file>.out file, four main files are formed, these are:
<file>.heats: A comparison of calculated and reference heats of formation.
<file>.geos: A comparison of calculated and reference geometric quantities (bond lengths, angles and dihedrals)..
<file>.ips: A comparison of calculated and reference ionization potentials.
<file>.dips: A comparison of calculated and reference dipole moments.
These files can then be used as data for generating tables comparing different methods, and for statistical analyses.
Note: To make the <file>.geos file, the geometry is allowed to relax. This is different from a parameter optimization, where the gradients of the geometric reference data are used.