Quantum Chemistry Tools

Quantum chemistry is the basis for the understanding of many phenomena in chemistry. Therefore students and chemists have to learn the basics of this field. We have developped two on-line services that allow the easy understanding of two major applications of quantum chemical computing.

OrbVis

OrbVis is an on-line service for the calculation and visualization of molecular orbitals (MOs). MOs describe the sojourn probabilty of electrons in atoms and molecules and are important for the understanding of reactions.
Our tool can compute and visualize MOs of any reasonable structure submited. The calculation of the 3D coordinates and the orbital vectors is handled on the server by chemistry programs. We thank Johann Gasteiger from the University of Erlangen for kindly allowing us to use the CORINA program. We also thank Tim Clark from the University of Erlangen for kindly allowing us to use the VAMP program. The results of the calculations are sent back to the client in a very condensed form as function parameters. The client starts a Java applet which provides functions to compute the electron density volume data from the orbital vectors. The advantage of this implementation-style is that only one HTML page and one applet have to be transmitted to the client instead of several large volume data sets. This methodology allows the interactive analysis of structure and volume data by balancing rendering quality and real time performance [3]. A prototype application for the time-dependent animation of volume data such as the changes of molecular orbitals during a chemical reaction has also been developed.

ComSpec3D

ComSpec3D [3] is an on-line tool for the calculation and visualization of Infrared and Raman spectra and their associated normal modes. Spectra can be described as fingerprints of molecules. Each spectrum is characteristic for a given molecule and can be used for its identification. The fingerprint contains absorption results in an oscillation of the atoms which is called a normal mode.
Our on-line service explains the relationships between the oscillation of a molecule and the corresponding spectrum. As already described for the OrbVis service, all chemical information will be computed on the server. The client receives a HTML page that includes an image of the spectra and a table with all corresponding normal modes. By clicking on the wavenumbers the user gets the associated 3D animated VRML scene of the normal mode. The animation of the atoms and bonds is implemented through a set of position interpolators for the scene objects, that operate on lists of precalculated 3D object coordinates (trajectories). After the VRML scene has loaded, the VRML plug-in is in charge of displaying the movement by interpolating the data points along these trajectories.