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ChemOffice.Com - CambridgeSoft

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A text box appears.<br />

4. Type F(C2F4)6F and press the Enter key.<br />

A polymer segment consisting of six repeat<br />

units of tetrafluoroethylene appears in the<br />

model window.<br />

To perform the computation:<br />

To review the results:<br />

1. View the Output window to examine the<br />

measurement data included in the molecular<br />

dynamics step data.<br />

2. Drag the Movie slider knob to the left until<br />

the first step appears.<br />

1. Select C(2), the leftmost terminal carbon, then<br />

Shift+click C(33), the rightmost terminal<br />

carbon.<br />

2. Choose Set Distance from the Measurement<br />

submenu of the Structure menu.<br />

A measurement for the overall length of the<br />

molecule appears in the Measurements table.<br />

3. Choose Molecular Dynamics from the MM2<br />

submenu of the Calculations menu.<br />

4. Click the Job Type tab and click the checkbox<br />

for Copy Measurements to Output. If you want<br />

to save the calculation as a movie, select Record<br />

Every Iteration checkbox.<br />

5. Click Run.<br />

When the calculation begins, the Output Window<br />

appears.<br />

To replay the movie:<br />

• Click Start on the Movie menu.<br />

The frames computed during the molecular<br />

dynamics calculation are played as a movie.<br />

Selected<br />

The C(2)-C(33) distance for the molecule<br />

before the molecular dynamics calculation<br />

began is approximately 9.4Å.<br />

3. Scroll down to the bottom of the Output<br />

window and examine the C(2)-C(33) distance<br />

for the molecule at 0.190 picoseconds (which<br />

corresponds to frame 20 in the Movie slider of<br />

the model window).<br />

The C(2)-C(33) distance is approximately<br />

13.7Å, 42% greater than the initial C(2)-C(33)<br />

distance.<br />

<strong>ChemOffice</strong> 2005/Chem3D MM2 and MM3 <strong>Com</strong>putations • 157<br />

Molecular Dynamics

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