CuGa(SSe1 − )2 alloys at high pressure: Optical absorption and X-ray diffraction studies

Crystallographic properties of the MnGa2Se4 compound under high pressure

“…9 Also, a transition to the cubic rocksalt type structure has been observed to occur in normal cubic zinc blende II-VI and tetragonal chalcopyrite I-III-VI 2 materials. 10 It was found that this cubic structure is stable up to the maximum pressure available in the present experimental measurements ͑P m = 25 GPa͒. The observed increase in coordination number, from 4 for a defect tetragonal structure to 6 for the cubic NaCl-type structure, is in agreement with the considerations indicated above.…”

“…However, it appeared that in the case of the normal II-VI and I-III-VI 2 materials, the transition is a reversible one. 10 It is seen from Fig. 3 that, in FIG.…”

“…where B 0 is the isothermal bulk modulus at P = 0, the dimensionless parameter B 0 Ј is the pressure derivative of the isothermal bulk modulus evaluated at zero pressure, and n 0 is 10,13,14 In Table II, the values of B 0 and B 0 Ј for the tetragonal phase were determined only when either neon or a mixture of methanolethanol was used to obtain the crystal parameter values. In the tetragonal field, parameters determined with silicon oil were not used in the calculations since it is well known that the transmitting properties of silicon oil become a little poor above 8 GPa.…”

Anomalous pressure dependence of acoustic phonons of AgGaSe2 investigated by inelastic neutron scattering to 4.3 GPa

“…(i) In the Cu-type compounds, the linear thermal expansion coefficients α a and α c are always positive at room temperature with α a < α c while in the Ag-type compound, α c is negative [2,3]. (ii) In the Cu compounds, the isothermal compressibility is χ a > χ c , while in AgGaSe 2 the c parameter is more compressible than the a parameter [4,5]. (iii) X-ray diffraction studies [5] have shown that the chalcopyrite structure of AgGaSe 2 is stable up to 2.6 GPa with successive phases at 2.6 -5 GPa (α-phase), 5-10 GPa (orthorhombic), 10 -18 GPa (tetragonal) and 18 -25 GPa (δ-phase).…”

Temperature-dependent absorption edge in AgGaS2 compound semiconductor

“…AgGaS 2 , an Ag compound, has been of particular interest due to its highly non-linear optical susceptibility and large birefringence [5]. As such, research on the basis properties of this material has focused on optical characterizations such as photoluminescence [6], photoreflectance [7], and optical absorption spectra [8]. In particular, anomalous band gap variation at low temperature (T < 100 K) remains a matter of debate.…”