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   mopac notes

The Silicon Graphics Teaching Laboratory
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Chemi cal Information Laboratory
and this information is for historical interest only

Mopac Notes

Mopac is a semi-empirical molecular orbital program, written by J J P Stewart. It incorporates the common semi-empirical Hamiltonians, AM1 and PM3.

To run Mopac use the rmopac command. Mopac is expensive in computer time, so you should use a local directory. Type rmopac filename where filename is a valid Mopac input file. You can make a Mopac input file from a Macromodel file. Draw the molecule you are interested in using Macromodel, then write it to a file called aardvark or any other suitable name. Quit Macromodel, and type mm2mop aardvark. This will create two new files: aardvark.mmod and aardvark.dat. The latter is a Mopac file. Run it by typing: rmopac aardvark. The answer to the question in the file will be put into a file called aardvark.out.

The file produced by this procedure will do a single point calculation on the structure that it is given. If you want the structure to be minimised, then type mm2mopM aardvark instead of mm2mop aardvark. This will produce a file that minimises the structure.

If you want to do a MOPAC calculation on every structure in a MacroModel output file, then use the mult2mop command. MOPAC calculations are much slower that molecular mechanics, so this command should be used with care. This program takes a multistructure MacroModel file, converts each structure into a Mopac input file, and minimises each one using AM1. The program creates a new directory called mult2mop.filename and makes a large number of files within it. The results are summarised in the file: filename.fe

mult2mop only works with the old format of MacroModel data file, and so the command m54 must be used to convert MacroModel 5.5 files to the old format.

Once you have run a Mopac calculation, you can change the output file back into MacroModel format by typing mop2mm aardvark.

If you are logged on to one of the Silicon Graphics Teaching Laboratory's Indigos, you can click here to read the Mopac help file or the manual. If you are not logged on to one of these machines, clicking on these hyperlinks will give you an error message.

Xed/Cosmic provides an interface to Mopac, and this is described in Practical Five: Viewing Orbitals.

VAMP is similar program.

© Goodman Group, 2005-2017; privacy; last updated October 21, 2017

department of chemistry University of Cambridge