Abstract:
Silicon is an indirect band gap semiconductor belonging to group III-V. It is commonly
used in light emitting diodes (LED) and many optoelectronic devices fabrications. In this
thesis, the structural, electronic and optical properties of silicon are investigated using
DFT and TDDFT with the help of Quantum ESPRESSO. A number of convergence test
were performed to establish the optimal value of various parameters in the numerical
calculations. Firstly, the total minimum energy of Silicon per atom was calculated as a
function of cutoff energy and k-points sampling. The results of calculations show that the
total minimum energy of Silicon per atom is monotonically decreasing with increasing
cutoff energy due to variational principle.However, this trend can not be predicted from
increasing the k-point sampling.Secondly, the optimal lattice constants of bulk silicon
was calculated using the results obtained from energy convergence test (i.e 50 Ry and 6 x
6 x 6 k-points).The equilibrium lattice constant was 5.43 Angestrom. The obtained result
was overestimated as compared to the experimental result. Moreover the band structure
and density of states of Silicon have been calculated based on the frame work of density
functional theory.The calculated band gap Energy of Silicon is 0.83 eV, which is closer to
the experimental value (1.12 eV). Finally the real, and imaginary parts of the dielectric
function and the electron energy loss function(EELS) were calculated using TDDFT .
Keywords: Silicon, density functional theory, pseudopotentials, plane wave self-consistent
field, Quantum Espresso Package,time dependent density functional theory(TDDFT)and,
turboEEL
