Abstract:
In this thesis the first principle calculation of tungsten disulfide (WS2) is investigated with density functional theory (DFT) using Quantum Espresso package. Our
study is based on Density Functional Theory (DFT) with the Perdew-Burke-Ernzerhof
(PBE) exchange-correlation functional, Vanderbilt (ultra soft) pseudopotentials and
the plane wave basis set implemented in the Quantum-ESPRESSO package. The
calculation of the total minimum energy and the total minimum force of WS2 is
calculated as a function of cutoff energy and K-points sampling. The total minimum energy per cell is monotonically decreasing with increasing cutoff energy due
to variational principle. However, this trend can not be predicted from increasing
the k-points sampling. Moreover, the equilibrium lattice constant is calculated using results obtained from energy convergence test (i.e., 90 Ry and 7 × 7 × 1 ). The
computational value of the equilibrium lattice constant is 3.23 ˚ A. This result is in
good agreement with experimental value wich is 3.18 ˚ A . Finally, discussing band
structure and density of state of two dimensional WS2, the electrical property of two
dimensional WS2 is determined based on energy band gap.
