Temperature‐ and pressure‐dependent phonon dynamics properties of gallium selenide telluride

Abstract

Understanding the thermodynamic properties of materials is a fundamental issue in physics, and its knowledge is crucial for targeting a specific material for possible applications. In this work, we report a temperature‐ and pressure‐dependent Raman study of bulk GaSe0.5Te0.5 alloy, besides their relevant thermodynamic parameters. Our results show a nonlinear redshift for the A1g and E2g vibrational modes as the temperature increases in the temperature range from 10 to 748 K. Such behavior is well described by considering both thermal expansion and phonon–phonon coupling contributions. By combining density functional theory (DFT) calculations and Raman spectroscopy experiments, the anharmonic constants relative to the three‐ and four‐phonon decay processes, mode‐Grüneisen parameters, Debye temperature, thermal expansion coefficient, and bulk modulus were estimated for GaSe0.5Te0.5 alloy. Furthermore, the high‐pressure measurements and DFT calculations, performed in the pressure range from 0 to 26.4 GPa, show a quadratic trend for the ωA1g and ωE2g modes as a function of pressure, with the A1g modes being more compressible than E2g one, that is, ∂ωA1g∂P>∂ωE2g∂P. No structural phase transition is observed until the maximum pressure reached in the experiment. This study took a step forward in the understanding of mechanical and thermal properties related to GaSe0.5Te0.5 alloy, whose determined parameters are important for designing new applications.

Pressure Tuning Resonance Raman Scattering in Monolayer, Trilayer, and Many-Layer Molybdenum Disulfide

“…Besides the thickness-dependent optical properties, external perturbations, such as strain, hydrostatic pressure, and temperature, have also been reported as tuners of physical properties in TMDs − and of other layered materials. − Among such approaches, pressure proves to be an effective way to change the structural, electronic, and optical properties of MoS 2 . In this material, a structural phase transition from the hexagonal 2H c to 2H a structure is reported at ∼20 GPa, followed by a semiconducting to metallic electronic transition. − Such a critical pressure scales with the decreasing sample thickness, and for 1L-MoS 2 , the closing of the gap is predicted to be reached at ∼68 GPa .…”

Raman spectroscopy and X‐ray diffraction of diphenylphosphoryl azide under high pressures

“…[ 6–12 ] As pressure can directly change the molecular structures and bonding patterns, high‐pressure techniques provide an excellent route to synthesize energetic polymeric nitrogen materials. [ 13–16 ] The high‐pressure studies of azides show that the electron orbital hybridization of the azide ions in inorganic azide leads to the occurrence of nitrogen polymerization. [ 17–22 ] However, the electron orbital hybridization in symmetric and linear azide ions is difficult to occur, which limits the researches and applications of polymeric nitrogen.…”