Ab-initio study of the stability and electronic properties of wurtzite and zinc-blende BeS nanowires

In this work we study the structural stability and electronic properties of the Beryllium sulphide nanowires (NWs) in both zinc blende (ZB) and wurtzite (WZ) phases with triangle and hexagonal cross section, using first principle calculations within plane-wave pseudopotential method. A phenomenological model is used to explain the role of dangling bonds in the stability of the NWs. In contrast to the bulk phase, ZB-NWs with diameter less than 133.3 (angstrom) are found to be less favorable over WZ-NWs, in which the surface dangling bonds (DBs) on the NW facets play an important role to stabilize the NWs. Furthermore, both ZB and WZ NWs are predicted to be semiconductor and the values of the band gaps are dependent on the surface DBs as well as the size and shape of NWs. Finally, we performed atom projected density-of states (PDOSs) analysis by calculating the localized density of states on the surface atoms, as well as on the core and edge atoms.Comment: 9 Pages, 6 Figure

Theoretical investigation of structural, electronic and optical properties of (BeS)(1) /(BeSe)(1), (BeSe)(1)/(BeTe)(1) and (BeS)(1)/(BeTe)(1) superlattices under pressure

The influence of hydrostatic pressure on structural, electronic and optical properties of short period (BeS)(1)/(BeSe)(1), (BeSe)(1)/(BeTe)(1) and (BeS)(1)/(BeTe)1 superlattices, has been investigated. The lattice parameters a and c for the tetragonal unit cell obtained by total energy calculations are in good agreement with the values calculated by macroscopic elasticity theory. The (BeS)(1)/(BeSe)(1) superlattice possesses an indirect band gap while (BeSe)(1)/(BeTe)(1) and (BeS)(1)/(BeTe)(1) superlattices possess a direct band gap. The pressure ranges from 0 to 47 GPa for (BeS)(1)/(BeSe)(1), 0 to 39 GPa for (BeSe)(1)/(BeTe)(1), and 0 to 45 GPa for (BeS)(1)/(BeTe)(1) , meanwhile the pressure dependence of the energy band gap along different symmetry directions obey the equation E-g(p)= E-g+ ap + bp(2). The pressure coefficient of the indirect band gap for (BeS)(1)/(BeSe)(1) is - 22.5675 x 10(-3) eV(GPa)(-1), while that of the direct band gap is estimated as - 25.8581 x 10(-3)eV(GPa)(-1) and - 24.4695 x 10(-3)eV(GPa)(-1) for (BeSe)(1)/(BeTe)(1) and (BeS)(1)/(BeTe)(1), respectively. The variation of the static dielectric constant with pressure is discussed.</p