You may want to consider an optical calculation, which calculates interband transitions, from which is retrieved the absorption coefficient and index, conductivity, real and imaginary dielectric constants, refractive index and reflectivity. From these plots you can see at what energies (in the visible region) the transitions are occurring.
Alternatively, perhaps a band structure calculation with density of states would be useful to you. Chris On 28 April 2010 10:32, Jonas Baltrusaitis <[email protected]> wrote: > I have a large primitive cell organic crystal that has red color to it. > Components of this crystal before reaction are white. I was wondering if > SIESTA can calculate some solid state (3D) electric response properties, > such as absorption-fluorescence spectra or bandgap information that would > allow to model and explain why some organic crystals fluoresce in the > visible while others don't > > I understand it is a broad topic so any references and examples of work > done in SIESTA on electric properties would be appreciated > > Jonas > >
