Mechanical, electronic, and optical properties of Bi2S3 and Bi2Se3 compounds: first principle investigations

Abstract

The structural, mechanical, electronic, and optical properties of orthorhombic Bi 2 S 3 and Bi 2 Se 3 compounds have been investigated by means of first principles calculations. The calculated lattice parameters and internal coordinates are in very good agreement with the experimental findings. The elastic constants are obtained, then the secondary results such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, anisotropy factor, and Debye temperature of polycrystalline aggregates are derived, and the relevant mechanical properties are also discussed. Furthermore, the band structures and optical properties such as real and imaginary parts of dielectric functions, energy-loss function, the effective number of valance electrons, and the effective optical dielectric constant have been computed. We also calculated some nonlinearities for Bi 2 S 3 and Bi 2 Se 3 (tensors of elasto-optical coefficients) under pressure.

Optical, electronic, and elastic properties of some A5B6C7ferroelectrics (A=Sb, Bi; B=S, Se; C=I, Br, Cl): First principle calculation

“…Figure 2 shows the real and imaginary of e v ð Þ together with the energy loss function. The results obtained showa manner similar to our recent works [63,64]. The e 1 behaves mainly as a classical oscillator.…”

Mechanical, electronic, and optical properties of the A4B6 layered ferroelectrics: ab initio calculation

“…The ij C determine the response of the crystal to external forces characterized by the bulk modulus, Young's modulus, shear modulus, and Poisson's ratio, and, therefore, play an important part in determining the stability and stiffness of the materials [16][17][18]. The present elastic constants are computed by using the "volumeconserving" technique [19].…”

“…The Hill average [24] was used to calculate the polycrystalline modulus in a manner similar to our recent works [17,18].Using the relations given above, the calculated bulk modulus, shear modulus, Young's modulus, and Poisson's ratio for SnS and GeS are given in Table 3. The bulk modulus is a measure of resistance to volume change by an applied pressure, whereas the shear modulus is a measure of resistance to reversible deformations upon shear stress [27].…”

Large Elasto-Optic Effect in EpitaxialPbTiO3Films

“…where are components of the strain tensor (in Voigt notation) and ∆ is the resulting strain-induced change in the inverse of the square of the refractive index [48][49][50]. More precisely, we only consider here the '1' and '2' components of the strain tensor (with the '1', '2' and '3' axes being along the pseudo- Cm phases of epitaxial PTO films, n 1 =n 2 =n o, which is known as the ordinary refractive index and n 3 =n e, which is termed the extraordinary refractive index.…”