Tip To return to the system default settings, from the Options menu select the Restore Default Settings command.

3.5 Calculating Structural Parameters

3.5.1 Calculating Distance Between Two Atoms

1. Switch to the Balls and Sticks view mode for better view of atoms.

2. Click the Calculate Distance Between 2 Atoms button _.

3. Click on any atom to select it, then move the mouse pointer over another atom to highlight them with the selection color. On the status bar you can see the distance between the selected atoms:

4. To fix the selection click on the atom. For example, in the picture below, the selected atoms are marked with green (for more details on how to set selection color, refer to Section 3.3.1).

5. To cancel the selection and to start a new measurement, click somewhere in an empty workspace. To stop using this tool, click on its button to deselect it.

3.5.2 Calculating Angle Between Two Bonds

1. Click the Calculate Angle Between 2 Bonds button .

2. Click two neighboring atoms which form a bond.

3. Move the mouse pointer to the third atom which makes a bond with the last selected one. The calculated angle value appears on the status bar, e.g.:

4. To fix the calculated value, click this atom:

5. To cancel the selection and to start a new measurement, click somewhere in an empty workspace. To stop using this tool, click on its button to deselect it.

3.5.3 Calculating a Torsion Angle

1. Click the Calculate Torsion Angle button .

2. Click two atoms participating in a common bond. The corresponding bond becomes selected.

3. In the same manner, click on two more atoms adjacent to a previously selected bond. The final result will be three adjacent bonds, participating in a torsion angle, which will be selected:

The calculated angle is reflected on the status bar, e.g.:

Note Without selecting the third bond, it is possible to look through the values of all possible torsion angles neighboring the last selected atom by moving the mouse pointer over adjacent atoms.

4. To cancel the selection and to start a new measurement, click somewhere in an empty workspace. To stop using this tool, click on its button to deselect it.

4. Creating an Animated GIF

Now you can create animated GIF files for your site with minimum effort, minimum cost, and maximum impact.

The GIF file format may not be as sophisticated as Java, Flash, ActiveX or more chemistry-oriented formats as RasMol and Chime, but these newer applications are not as accessible to casual Web visitors who may not have the appropriate plug-ins or a connection that is fast enough. For true accessibility, a GIF file is still the cornerstone of Web design.

Animated GIFs are a nice touch for many a Web page, whether to emphasize something on the page (e.g. the "New" revolving spheres on the ACD download page) or to show, pictorially, something which is better sketched while explaining it to someone (e.g. electron density movement in the course of a Diels-Alder reaction).

4.1 Obtaining the Animation Software

Animated GIFs can be created with commonly available software such as packages listed through the Tucows site.[2] Such software is often freeware, evaluation ware, or shareware. (Standard disclaimer here: ACD makes no recommendation or claim for one animation product over another.) For the present example, we used Animagic shareware from RTL Software, Inc. An evaluation or shareware copy can be downloaded from the Web page

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Viewing 3D Structures 使用指南(8)