courses in kinetics or molecular reaction dynamics. Included with the software are sample simulations, accompanied by explanations i n the documentation, which demonstrate some of the important concepts of reaction dynamics.
Molecular Dynamics of the F + Hz Chemical Reaction H. Douglas Kutz, Jonathan H. Copeland, and George T. Mathai University of Tennessee at Chattanooga Chananooga, TN 37403
Potential energy surfaces and reaction dynamics are standard topics in undergraduate physical chemistry courses. Examining chemical reactions in terms of atomiclevel wllisions is important in general chemistry courses as well. From an educational standpoint, a major consideration in studying atomic-level collisions is the visualization process that is required. It is common to find in chemistry textbooks static, cartoon-like drawings of colliding atoms and molecules. A much more effective representation of atomic-level collisions involves a dynamic animation of events. During the past several years microcomputers have developed significantly in memory and speed. I t is now possible to perform simulations of atom-molecule collisions on a microcomputer. The program presented in this work examines collisions between a fluorine atom and a hydrogen molecule. The F + Hz reaction is studied in terms of the potential energy surface and also in terms of the reaction dynamics associated with this reaction. In the software presented in this work the potential energy surface for the collinear F + Hz system is examined. Bond lengths, bond energies, the transition state, the barrier height, and the reaction exothermicity are identified. Both wire-frame models and contour plots are presented. Several F + Hz wllinear collisions are presented in the reaction-dynamics portion of the program. Each collision may be viewed as an animation that shows the F atom and the vibrating Hz molecule approaching each other, forming the F-H-H transition state, and finally yielding H + HF products. The wllision may also be viewed as the motion of the system point on the contour plot of the potential energy surface. This viewing mode demonstrates clearly how the course of the collision is determined by the features of the potential energy surface. The program leads the user in
A, bond length
investigating how the reagent energy effects the F + Hz collision and on how the product H + HF energy is distributed. The program also allows the user to create new F + HZcollisions. This program would be useful in a general chemistry class. As a demonstration or tutorial, it could be employed to present a number of the aspects of atomic-level collisions that are wvered in general chemistry courses. The program is ideally suited for use in physical chemistry courses. The first portion of the program would be of considerable benefit in helping the user develop a n understanding of potential energy surfaces and related concepts. The second portion of the program would provide the user with an excellent introduction to reaction dynamics. The highly visual and dynamic aspects of this program make it an interesting and effective learning resource.
About This lssue John W. Moore Jon L. Holmes University of Wisconsin-Madison Madison, WI 53706
The programs in this issue of JCE: Software cover subjects that have been previously represented in this Journal. "The Acid-Base Package" brings to the Macintosh a derivation of the MS-DOS version ( I ). It provides the same functionality of its predecessor in a single program and adds the graphical interface of the Macintosh to simulate the laboratory actions of getting chemicals from the stockroom, adding them to a beaker, and performing an action on the solution in the beaker such as measuring its pH or titrating it. "Reaction Dynamics" and '%folecular Dynamics of the F + Hz Chemical Reaction" use the computer to graphicallv disolav and animate the atomic level interactions ~~~~~-~ that occur in simple atom-molecule chemical reactions as was similarly presented previously by Kutz (2). The dynamic display of atomic level phenomena with interactive student control of the reaction parameters involved dramatically illustrates one of the great advantages of the microcomputer over traditional textbook illustrations.
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Hardware Requirements The programs in this issue of JCE: Software will run on a Macintosh Plus, SE or SEl30, Classic or Classic 11, any Macintosh 11, Qnadra, or PowerBook. "The Acid-Base Package" requires System 6.0.4 or greater. 'Reaction Dynamics" and "Molecular Dynamics of the F + Hz Chemical Reaction" requires System 4.2 and Finder 6.0 or greater. Each program can be run from an 800K disk drive; a hard disk is not required. All the programs in this issue are compatible with System 7. To Order This lssue Journal of Chemical Education: Software (often called JCE: Software) is a publication of the Journal of Chemical Education. There is an Order Form card inserted in this issue. If this card is not available, wntact: JCE: Software, Department of Chemistry, University of Wisconsin-Madison, 1101University Avneue, Madison, WI 53706; 60812625153 (voice); 6081262-0381 (FAX). Citations
Flg~re2 Skewed, mass-weignted wire-frame potentla1 energy surface of tne F + r12react on wath the rl-H bono length an0 energy shown.
1. RameUe, Richard W.'The Acid-Rasp Package",J Chrm. Edur: Sofiwzm 1389,IIB (7 1
2. Kutz, Douglas "Animation of an Atom-Molede Chemical Reaction",J. Cham Edue: Wmre 1991,IIICiZJ.
Volume 69 Number 12 December 1992
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