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ChemOffice.Com - CambridgeSoft

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The following table contains the keywords<br />

automatically sent to MOPAC and those you can<br />

use to affect this property.<br />

Keyword<br />

UHF<br />

Description<br />

Automatically sent to MOPAC if<br />

you choose “Open Shell<br />

(Unrestricted)” wave functions to<br />

specify the use of the Unrestricted<br />

Hartree-Fock methods.<br />

UHF Spin Density<br />

The UHF Spin Density removes the closed shell<br />

restriction. In doing so, separate wave functions for<br />

alpha and beta spin electrons are computed. For<br />

more information see the MOPAC online manual,<br />

page 152.<br />

The following table contains the keywords<br />

automatically sent to MOPAC and those you can<br />

use to affect this property.<br />

Keyword<br />

Description<br />

Hyperfine<br />

GEO-OK<br />

Automatically sent to MOPAC to<br />

specify the hyperfine computation.<br />

Automatically sent to MOPAC to<br />

override checking of the Z-matrix.<br />

UHF<br />

Automatically sent to MOPAC if<br />

you choose “Open Shell<br />

(Unrestricted)” wave functions to<br />

specify the use of the Unrestricted<br />

Hartree-Fock methods.<br />

MMOK<br />

Automatically sent to MOPAC to<br />

specify Molecular Mechanics<br />

correction for amide bonds. Use<br />

the additional keyword NOMM to<br />

turn this keyword off.<br />

Spin Density<br />

Spin density arises in molecules where there is an<br />

unpaired electron. Spin density data provides<br />

relative amounts of alpha spin electrons for a<br />

particular state.<br />

Spin density is a useful property for accessing sites<br />

of reactivity and for simulating ESR spectra.<br />

Two methods of calculating spin density of<br />

molecules with unpaired electrons are available:<br />

RHF Spin Density and UHF Spin Density.<br />

GEO-OK<br />

MMOK<br />

SPIN<br />

Automatically sent to MOPAC to<br />

override checking of the Z-matrix.<br />

Automatically sent to MOPAC to<br />

specify Molecular Mechanics<br />

correction for amide bonds. Use<br />

the additional keyword NOMM to<br />

turn this keyword off.<br />

You can add this keyword to print<br />

the spin density matrix in the *.out<br />

file.<br />

RHF Spin Density<br />

RHF Spin Density uses the 1/2 electron correction<br />

and a single configuration interaction calculation to<br />

isolate the alpha spin density in a molecule. This<br />

method is particularly useful when the UHF Spin<br />

Density computation becomes too resource<br />

intensive for large molecules. For more information<br />

see the MOPAC online manual, page 28.<br />

<strong>ChemOffice</strong> 2005/Chem3D MOPAC <strong>Com</strong>putations • 185<br />

<strong>Com</strong>puting Properties

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