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Version 8.0   June 2008

MOPAC Interface

J.M.H. Thomas

0.1 GAMESS-UK/MOPAC Interface

This document is the original MOPAC 7.0 Manual written by Dr. James J. P. Stewart with a section pre-pended to it that serves to document the directives that allow users of GAMESS-UK to drive MOPAC from within GAMESS-UK. The original MOPAC manual is freely available for download on the web at: \

No changes have been made to the manual itself, bar the inclusion of this section.

The MOPAC interface within GAMESS-UK allows MOPAC to be run from a standard GAMESS-UK input file. The MOPAC version that is supplied with GAMESS-UK is version 7.0

The interface between GAMESS-UK and MOPAC currently permits geometries from a MOPAC run to be imported into GAMESS-UK for incorporation in a standard GAMESS-UK calculation. This permits users to run, for example, a quick optimisation with the AM1 semi-emprical method before importing the optimised geometry into GAMESS-UK to run a full ab inito calculation.

There are example input files for running MOPAC from within GAMESS-UK in the directory:


0.1.1 Running MOPAC from GAMESS-UK

The MOPAC directives should be included in a standard GAMESS-UK input file and must appear before any GAMESS-UK directives. The first line of the input file should consist of the single keyword MOPAC (in A format). A standard MOPAC input (as described in the rest of this manual) should then follow, terminated by a single blank line.

With an input of this format, all that will happen is that GAMESS-UK will drive MOPAC, and the output produced will be a standard MOPAC output prepended with the some minimal output generated by the GAMESS-UK input processor.

An example of a such a simple MOPAC job is below, which shows a MNDO calculation on water, run for a single SCF cycle.

The input for this example is the file:

mndo 1scf

o 1 1
h 1 1 111 1

0.1.2 Using MOPAC together with GAMESS-UK

As described above, GAMESS-UK serves as little more than a wrapper for running MOPAC. Of greater interest is the use of the results generated by MOPAC in a GAMESS-UK run. Currently, the only data that can be exported from MOPAC for use by GAMESS-UK are the atomic coordinates, allowing MOPAC to serve as a quick optimiser for GAMESS-UK.

For this to work, the directive out=gamess must be included on the MOPAC keyword line (the first line of the MOPAC directives). This instructs MOPAC to create an archive file that stores the coordinates for retrieval by GAMESS-UK.

Following the MOPAC directives, there should be a blank line followed the keyword ''GAMESS'' (in A format), indicating the start of the GAMESS-UK directives. From this line onwards, the directives should just be standard GAMESS-UK directives.

To use the geometry from a MOPAC run in a GAMESS-UK job, the flag ''MOPAC'' should be appended to the GAMESS-UK GEOMETRY keyword, as demonstrated in the example below.

The input for this example is the file:

	  prec density local vect mullik pi bonds xyz graph pm3 out=gamess
	  " "
	  0008 -1.2166   0001 -0.0214   0001 0.0000    0001 0000 0000 0000
	  0006 0.0028    0001 0.0032    0001 0.0000    0001 0000 0000 0000
	  0006 0.7539    0001 1.3084    0001 0.0000    0001 0000 0000 0000
	  0006 0.7915    0001 -1.2794   0001 0.0000    0001 0000 0000 0000
	  0001 0.5285    0001 -1.8623   0001 -0.8951   0001 0000 0000 0000
	  0001 0.5285    0001 -1.8623   0001 0.8951    0001 0000 0000 0000
	  0001 1.8767    0001 -1.0977   0001 0.0000    0001 0000 0000 0000
	  0001 1.3862    0001 1.3756    0001 -0.8976   0001 0000 0000 0000
	  0001 1.3862    0001 1.3756    0001 0.8976    0001 0000 0000 0000
	  0001 0.0485    0001 2.1532    0001 0.0000    0001 0000 0000 0000

	  acetone 6-31g geometry optimisation from mopac starup
	  geometry mopac
	  basis 6-31g
	  runtype optxyz
	  xtol 0.003
	  enter Specifying the archive file to use

By default MOPAC will create an archive file called archive containing the coordinates, and this is what GAMESS-UK will expect to find. If however a file named archive already exists in the directory, MOPAC will create one called archiveaa, or if this exists, one called archiveab etc. If an archive file called ''archive'' cannot be found when GAMESS-UK attempts to import the geometry then it will crash with the following error message:

          0: GAMESS-UK Error: requested archive file missing or empty

It is possible to tell GAMESS-UK which archive file to look for by setting the envirnment variable ''archive'' to the name of the file before the job is run. This shown below for the Bourne/BASH shells.

          archive=myarchive; export archive

This also allows one to use geometries stored in MOPAC archive files from previous runs, by setting the ''archive'' environment variable to point to the relevant file and then inserting the ''GEOMETRY MOPAC'' directive in a standard GAMESS-UK input file.

MOPAC Manual (Seventh Edition)
Dr James J. P. Stewart

January 1993

This document is intended for use by developers of semiempirical programs and software. It is not intended for use as a guide to MOPAC.

All the new functionalities which have been donated to the MOPAC project during the period 1989-1993 are included in the program. Only minimal checking has been done to ensure conformance with the donors' wishes. As a result, this program should not be used to judge the quality of programming of the donors. This version of MOPAC-7 is not supported, and no attempt has been made to ensure reliable performance.

This program and documentation have been placed entirely in the public domain, and can be used by anyone for any purpose. To help developers, the donated code is packaged into files, each file representing one donation.

In addition, some notes have been added to the Manual. These may be useful in understanding the donations.

If you want to use MOPAC-7 for production work, you should get the copyrighted copy from the Quantum Chemistry Program Exchange. That copy has been carefully written, and allows the donors' contributions to be used in a full, production-quality program.

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