Abstract:
Nano-dimensional crystalline cadmium sulfide is a semiconductor that exhibits size-dependent optoelectronic properties, determined by the effects of quantum confinement. Due to these effects, it is
possible to adjust the optical properties of the final cadmium sulfide clusters by varying their size. In
this work we report the results of a theoretical study of CdS nanoparticles with the methods of the
density functional tight-binding (DFTB) and the time-dependent density functional theory TD DFT. The
calculations of the electronic absorption spectra of CdS crystals were performed on cadmium sulfide
nanoparticles with an amount of from 5 to 137 atoms. The DFTB method was used for the structural
optimization of the studied nanoparticles. The optimization results showed that the clusters will be a
wurtzite structure and the geometrical parameters of the structure are close to the known experimental
data for a CdS crystal. For the obtained optimized structures, the electronic absorption spectra were
calculated by the linear response methods in the DFTB approximation and the time-dependent density
functional theory of the TD-DFT approximation. It is shown that the data obtained by the DFTB method
are close to those that can be obtained using DFT calculations for cadmium sulfide clusters. Especially
good agreement is obtained when using large clusters with small values of the dipole moment.
