PARAM is a program for optimizing parameters for semiempirical methods. It is controlled by a single data set that specifies the type of operation (usually parameter optimization or a survey to determine errors), the conditions for the operation (PM6, PM6-D3H4X, PM7, etc., or a new method), and the sets of data-files to be used.
Given one or more sets of reference data, the program PARAM can optimize parameters for elements for use in semiempirical methods.
The program PARAM is the central program used for method development. There are several utility programs (see UTILITY PROGRAMS) that are useful in manipulating the large files and large number of files. Before using the program PARAM, first become familiar with these utilities.
PARAM uses several types of files. For convenience, these should be stored in different folders, so each folder contains only one type of file. The main types are normal data sets, data sets representing atomic states, data sets for exotic systems, and data sets for intermolecular interactions. PARAM can handle 15,000 reference data in 10,000 reference data files and 4,000 parameters.
If, as is inevitable, things go wrong, there are extensive diagnostics available for finding out what happened. These diagnostics can also indicate what to do, but of course they cannot take any action on their own. Options also exist to identify faulty data, and, depending on the keywords used, either ignore, i.e., exclude, the faulty data or stop the calculation, so the user can take appropriate action.
Causes of error in Semiempirical methods