Of the computer visualization packages available to help students learn symmetry and group theory, most can be categorized as tutorials (1-2), multimedia presentations (3-4), or computer-assisted instruction (5-6), and possess little user interactivity. Others incorporate sophisticated Web tools including the Chime (7) and Shockwave (S) browser plugins, or Java applets (9) but, again, are only modestly user interactive. The most instructive and versatile of these (8) lists all of the symmetry elements for each of the 47 molecules available in its internal library, and allows the user to run an impressive Shockwave animation illustrating the corresponding symmetry operation. Although such programs are helpful in familiarizing students with the concepts, once the fundamentals have been taught, students should, be able to practice their skills in a visualization environment that is free from the kind of predetermined flow of information that characterizes these programs. Specifically, they should be able to define a symmetry element anywhere in any molecule and determine the effect of the corresponding symmetry operation. Such freedom allows students to capitalize on the most important aspect of interactive learning-to make mistakes and to learn from them. In this context, we have developed SymmetryApp, a new visualization program characterized by a high level of user interactivity.
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