In this Research at Undergraduate Institutions (RUI) grant, first-principles, density functional theory cluster calculations will be used to study the Raman-active modes of IV-VI chalcogenide glasses GexSe1-x and SixSe1-x . The Raman spectra of these materials exhibit clear signs of the rigidity transition predicted for glasses as a function of x. The object of the calculations is to link the observed changes in the Raman spectral features to corresponding changes in the underlying atomic structure. In this way the calculations will lead to a more detailed understanding of the rigidity transition and of the short and intermediate range order in these materials.
This research project will feature systematic studies of cluster models of the glasses. The clusters will each contain one or more of the basic structural units of the glass. The vibrational modes of each cluster will be computed using standard methods and then the absolute Raman spectral intensities for these modes will be computed from first-principles using a new DFT-based technique. The calculations will produce predicted Raman spectra that can be compared directly to experimental results. The comparisons will serve to identify the short-rang order responsible for the characteristic spectral features. In addition, the calculated absolute Raman intensities can be used to predict the relative concentrations of basic structural units in the glass. This is an entirely new capability that will b used for the first time in this project. The concentration information is fundamental to many questions regarding the structure of the glasses and to important details of the rigidity transition. Both undergraduates and masters students will participate in this project.
This is an RUI award to support theoretical research on the properties of glassy semiconductors. Both undergraduate students and masters students will participate.
|Effective start/end date||07/1/99 → 06/30/03|
- National Science Foundation: $96,000.00