Zn11Se11, Zn11S11, and ternary alloys from Zn11SnSe11-n (n = 1 - 11), with cubic structures represented by nanostructures called tetramantane, have been studied theoretically by investigating the electronic properties, Raman and UV-vis spectra. LUMO and HOMO levels were observed to change with the number of the sulfur atoms. The (HOMO - LUMO) gap for Zn11Se11 (2.377205eV) increased with the sulfur atoms. Zn11S8Se3 was calculated to have an energy gap (3.061305eV) less than others ternary alloys. The calculated energy gap of Zn11S11 (3.597374eV) is in a high agreement with experimental value (3.6 eV). Raman spectra for ternary alloys Zn11SnSe11-n content peaks result from the connection of (Zn11Se11+Zn11S11) peaks, Zn11Se11 has peak at 260.42 cm-1 shifts from the experimental value by a small deviasion which is produced due to the confinement effect. UV-vis spectra for ternary alloys shifted to a higher energy level with the increase in the number of sulfur atoms and dramatically close to Zn11S11 UV-vis spectrum except Zn11S8Se3 has λmax at 342 nm. These nanostructures are suitable to be used in different applications such as lenses, photoelectronic devices, solar energy, and biosensors. DFT/TDDFT at the B3LYP level with SDD basis functions is used. All the calculations are completed using the Gaussian 09 program.