PRAXIS / P / FIS /14 188 / 1998
Jorge A. Trindade
Tope of the page
Virtual reality adds a new dimension - immersion - to
graphics display. Moreover, the characteristics of this new
technology allow for a greater interactivity with the user.
The Virtual Water project is a virtual environment applied to the learning and teaching of Physics and Chemistry. The project involves aspects as atomic and molecular orbits, electronic densities, bonds, phase transitions, etc.
It is a multidisciplinary work involving areas as computational simulation of physical and chemical systems, computer graphics and science education.
Partners of this project are Centro de Computação Gráfica, Coimbra, Exploratório Infante D. Henrique, Coimbra, Physics Department of the Instituto Superior Técnico, Lisboa, and High Education School for Technology and Management, Guarda.
The recourse to
graphics, in particular to three-dimensional ones, for
visualizing and interpreting information has been increasing in
the research and teaching of sciences. In particular, that
recourse is needed in domains where the interpretation of complex
information is more demanding, as it happens in molecular
modelation. The reasons for such interest are clear: in
scientific research it is easier to obtain understanding from a
three-dimensional model than from the simple reading of numbers
or formulas; in the apprenticeship domain the utility of
graphical methods, in particular the immersive ones, is being
proved, for instance for forming correct conceptual models .
The Virtual Water project aims at the conception of an educational environment, joining molecular modelation with immersive three-dimensional graphic representation. The choice of water is justified by the fact that this is a common and relatively simple substance. Its study has interested many investigators who do realistic simulations of water in Physics, Chemistry and Biology [2,3]. However, less attention has been given to the pedagogical exploration of water simulations.
The subjects approached in the project go from the study of the molecule geometry to the structures of the solid, liquid and gaseous phases, through the study of the electronic density and the chemical bonding by hydrogen bridges. The water model is based on the SPC (Simple Point Charge) model. Since some studies of water start with atomic orbits, in particular with the hydrogen s, p and d, this subject is also included in the project.
General Features of the Project
The exploration of the contents is done in two ways (Figure 1):
Figure 1 - Scheme of the environment Virtual Water. The yellow line denotes the content exploration going from the macroscopic to the microscopic side while the red line denotes the exploration going from the microscopic to the macroscopic side.
In any case, the
scenery exploration is preceded by navigation in a training
environment. The goal is to help the user to achieve good
adaptation to the interfaces (glove and Head Mounted Display),
navigation and interaction in virtual worlds.
The project is being done in two phases.
The first includes the visualisation of some quantum mechanics aspects:
Figure 2 The ball-and-stick geometry of the water. (Click here for the VRML format)
Figure 3 The fourth occupied molecular orbital of water from the Molecular Orbital Virtual Scenery. Calculations have been performed with "PC Gamess" (a program for ab initio quantum chemistry) and visualisation with "Molden" (a package for displaying molecular densities). (Click here for the VRML format)
Figure 4 The electronic density of the water. Calculations have been performed with "PC Gamess" (a program for ab initio quantum chemistry) and visualisation with "Molden" (a package for displaying molecular densities). (Click here for the VRML format)
Figure 5 The 3dz2 wave
function. (Click here for the VRML
The second phase concludes the molecular dynamics of:
Figure 6 The CPK model of the water solid phase. (Click here for the VRML format)
Figure 7 a frame of the phase liquid molecular dynamics of the water.
Since in many cases quantum effects in the dynamics of the atoms is small, The molecular dynamics on Virtual Water is an ab initio simulation based on Lennard-Jones potential and Newtonian mechanics. With the increased speed and availability of computing resources, it is coming more and more common to model systems atom by atom, moving each atom or molecule in response to the forces acting on it. Many experiments give insight into the structure and dynamics of water, but there are strong limitations to the general use of these experiments. For one thing, the experimental apparatus are expensive. Second, not all desired state points of the phase diagram of water are easily accessible. For example, it is very difficult to do experiments at the critical point of water, or with super heated or super cooled water. From simulations like these one can better interiorize microscopic models and better understand the substance's behaviour.
For implementing the virtual environment we use the WorldToolkit software that serves the definition and creation of the virtual scenarios and the following hardware: two PC's with Pentium II at 300 MHz, with 128 Mb of RAM, in network, using an accelerator graphic board Matrox Millennium II AGP with 8 Mb of RAM. For the navigation and immersion in the virtual environment, we use the Head Mounted Display V6 from Virtual Research, as well as one Cyberglove from Virtual Technologies and a position sensor to two receptors, Isotrack II, from Polhemus (Figure 8).
Figure 8 The virtual reality hardware used on virtual water project
The final product of this work will be disposed to the school community through the Competence Center "Nónio-Softciências".
The use of graphics is, indeed, a powerful tool for visualizating and understanding of complex and/or abstract information. The immersion capacity is a recent aspect to be explored and evaluated. A virtual environment for the teaching of Physics and Chemistry is being developed to test the possibility of applying virtual reality in teaching and learning. The work is in a preliminary phase of execution, so that its evaluation cannot yet be done.
The authors thanks Prof. Doctor Victor Gil, from the Chemistry Department of the University of Coimbra, for his suggestions, and Prof. Doctor José Carlos Teixeira, from the Computer Graphics Center of the same University for equipment and software facilities.
 J. Trindade e C. Fiolhais, "A Realidade Virtual no Ensino e Aprendizagem da Física e da Química", Gazeta da Física, Vol. 19, Fasc. 2, Abril/Junho, 1996, p. 11.
 M. Sprik, "Hydrogen bonding and the static dielectric constant in liquid water", J. Chem. Phys. 95 (1991), p. 6762.
 K. Laasonen, M. Sprik and M. Parrinelo, "Ab initio liquid water", J. Chem. Phys. 99 (1993), p. 9080.
 J. Douglas, " Visualization of electron clouds in atoms and molecules ", J. of Chem. Educ. 67, 1 (1990), p. 42.
 PC Gamess, a program for ab initio quantum chemistry, written by Alex. A. Granovski, Moscow State University.
 Molden, a package for displaying molecular density, written by G. Schaftenaar, CAOS/CAMM Center Nijmegen, Toernooiveld, The Netherlands.
 C. Fiolhais e J. Trindade, "Use of Computers in Physics Education", Proceedings of the "Euroconference'98 - New Technologies for Higher Education", Aveiro, Setembro (1998)
 C. Fiolhais e J. Trindade, "Física Para Todos - Concepções
Erradas em Mecânica e Estratégias Computacionais", 1
Colóquio de Física do Instituto Politécnico de Tomar
"A Física no Ensino na Arte e na Engenharia", Novembro
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