sir,
I am working on optical properties of ZnS nanotube armchair(3, 3) (4, 4) and chiral(4, 2) and zigzag(5, 0) all are showing band gap between 3.67 to 4 eV. All are the semiconductor. When I am calculating optical properties of all these nanotubes, I am getting the graph of the absorption coefficient, dielectric constant and refractive index (w.r. t. to energy eV). the origin of all these graphs starts from equal to its band gap of the nanotube. The dielectric constant and refrective index graph looks same as the absorption coefficient. But when I adsorbed phosphorous on all nanotubes and found zero eV band gap
also calculating optical properties as above for all adsorbed phosphorous ZnS nanotubes. the origin of all the graph absorption coefficient imaginary dielectric constant and refractive index start from 0 eV. but peaks refractive index and imaginary dielectric constant in the graph are not same as like as absorption coefficient graph. while it is posible in case of pristine ZnS nanotube.