  The microscopic structure of two amorphous materials with extreme nonlinear
optical properties has been studied. One of these materials exhibits second
harmonic generation, while another material of similar molecular structure
emits brilliant white light if being irradiated with a simple IR laser diode.
Structural differences were investigated using X-ray scattering and EXAFS
combined with molecular RMC. Transmission electron microscopy and scanning
precession electron diffraction were used to understand specific structural
differences on all length scales, from mesoscopic down to mutual molecular
arrangements. Characteristic differences were found at all scales. Close
core-core spacing between {SnS} clusters as well as characteristic cluster
distortions appear to be characteristic features of the white light emitting
material. In the other material, cores are undistorted and core distances are
larger. There, the formation of nanocrystalline structures in the amorphous
matrix could also be identified as reason for the WLG suppression.
