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Chapter 10: MOPAC <strong>Com</strong>putations<br />

Overview<br />

MOPAC is a molecular computation application<br />

developed by Dr. James Stewart and supported by<br />

Fujitsu Corporation that features a number of<br />

widely-used, semi-empirical methods. It is available<br />

in two versions, Professional and Ultra.<br />

MOPAC Pro allows you to compute properties<br />

and perform simple (and some advanced) energy<br />

minimizations, optimize to transition states, and<br />

compute properties. The CS MOPAC Pro<br />

implementation supports MOPAC sparkles, has an<br />

improved user interface, and provides faster<br />

calculations. It is included in some versions of<br />

Chem3D, or may be purchased as an optional<br />

addin.<br />

MOPAC Ultra is the full MOPAC<br />

implementation, and is only available as an optional<br />

addin. The CS MOPAC Ultra implementation<br />

provides support for previously unavailable<br />

features such as MOZYME and PM5 methods.<br />

In both cases, you need a separate installer to install<br />

the MOPAC application. Once installed, either<br />

version of MOPAC will work with either version of<br />

Chem3D.<br />

NOTE: If you have CS MOPAC installed on your<br />

computer from a previous Chem3D or <strong>ChemOffice</strong><br />

installation, upgrading to version 9.0.1 will NOT remove<br />

your existing MOPAC installation. Chem3D will continue<br />

to support it, even if the update version does not include CS<br />

MOPAC. Installing either of the CS MOPAC 2002<br />

versions will replace the existing MOPAC installation.<br />

CS MOPAC provides a graphical user interface that<br />

allows you to perform MOPAC computations<br />

directly on the model in the Chem3D model<br />

window. As a computation progresses, the model<br />

changes appearance to reflect the computed result.<br />

In this section:<br />

• A brief review of semi-empirical methods<br />

• MOPAC Keywords used in CS MOPAC<br />

• Electronic configuration (includes using<br />

MOPAC sparkles)<br />

• Optimizing Geometry<br />

• Using MOPAC Properties<br />

• Using MOPAC files<br />

• <strong>Com</strong>putation procedures, with examples.<br />

• Minimizing Energy<br />

• <strong>Com</strong>puting Properties<br />

• Optimizing to a Transition State<br />

• <strong>Com</strong>puting Properties<br />

• Examples<br />

• Locating the Eclipsed Transition State of<br />

Ethane<br />

• The Dipole Moment of Formaldehyde<br />

• <strong>Com</strong>paring Cation Stabilities in a<br />

Homologous Series of Molecules<br />

• Analyzing Charge Distribution in a Series<br />

Of Mono-substituted Phenoxy Ions<br />

• Calculating the Dipole Moment of meta-<br />

Nitrotoluene<br />

• <strong>Com</strong>paring the Stability of Glycine<br />

Zwitterion in Water and Gas Phase<br />

• Hyperfine Coupling Constants for the Ethyl<br />

Radical<br />

• RHF Spin Density for the Ethyl Radical<br />

<strong>ChemOffice</strong> 2005/Chem3D MOPAC <strong>Com</strong>putations • 161

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