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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 />

A model of formaldehyde appears.<br />

Administrator<br />

Keyword<br />

ESR<br />

Description<br />

Automatically sent to MOPAC to<br />

specify RHF spin density<br />

calculation.<br />

GEO-OK<br />

MMOK<br />

Example 1<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 />

The Dipole Moment of<br />

Formaldehyde<br />

To calculate the dipole moment of formaldehyde:<br />

1. From the File menu, choose New Model.<br />

2. Click the Text Building tool.<br />

3. Click in the model window.<br />

A text box appears.<br />

4. Type H2CO and press the Enter key.<br />

5. From the MOPAC Interface menu of the<br />

Calculations menu, choose Minimize<br />

Energy.<br />

6. On the Theory tab, choose AM1.<br />

7. On the Properties tab, select Dipole.<br />

8. Click Run.<br />

The results shown in the Messages window indicate<br />

the electron distribution is skewed in the direction<br />

of the oxygen atom.<br />

Dipole<br />

(vector<br />

Debye)<br />

X Y Z Total<br />

-2.317 0.000 -0.000 2.317<br />

If you rotate your model, the X,Y, and Z<br />

components of the dipole differ. However, the total<br />

dipole does not. In this example, the model is<br />

oriented so that the significant component of the<br />

dipole lies along the X-axis.<br />

186•MOPAC <strong>Com</strong>putations<br />

<strong>CambridgeSoft</strong><br />

<strong>Com</strong>puting Properties

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