LSI is the place of birth of the Ab-Initio Bethe-Salpeter Equation (BSE) method.
Indeed, in 1995 (Phys. Rev. Lett. 75, 818 (1995)) there was the first ab-initio application of the Bethe-Salpeter Equation to the calculation of the Optical Absorption spectrum of a cluster: Na₄. The method has shown its capability to correctly reproduce excitons and excitonic effects. Since then, the approach has been applied to calculate the optical spectrum with excitonic effects of bulk insulators (Li₂O 1997), semiconductors (Si, 1998), and to calculate the Energy-Loss spectrum of semiconductors (Si, 2001).

Optical Absorption of Silicon	Refraction Index of Silicon	EELS of Silicon
Optical Absorption of Solid Argon	Hydrogen series in Solid Argon