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February 20, 2004


How do I create my own parameters for Chem3D?


If you wish to create your own parameters for use in model building or minimization, you can do so without altering the files provided. When Chem3D loads parameters to create its internal tables, it reads all files in the C3DTABLE directory and concatenates them together. Therefore, you can create your own separate parameter files, place them in the C3DTABLE directory, and have them automatically appended to the standard ones.

For example, suppose you have a set of MM2 atom types which apply to a particular class of heterocycles. You can:

(a) Create your own small table of these parameters, and use it as a supplement to the standard list. Using the Templates menu in the Table Editor, select MM2ATYPE.TBT to open a new, empty table. Use the Edit menu to create new records, and then fill in the data. Save the completed file in the C3DTABLE directory, for example with the name MYATYPES.TBL. Chem3D will then automatically use this table in addition to the standard MM2ATYPE.TBL.


(b) Modify the existing set of parameters to include your own. In the Table Editor, open MM2ATYPE.TBL, and use Save As to save a backup copy in a directory other than C3DTABLE. Edit the table as desired, modifying or deleting existing records and adding your own. Save the edited file in the C3DTABLE directory with whatever name you choose. Chem3D will use this table the next time it needs these parameters.

If there are conflicts (multiple definitions of the same parameter) results are undefined. If you want to define your own value, be sure to delete any existing one.

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