Vibrational properties of δ-AlOOH under pressure
نویسندگان
چکیده
We have performed first-principles calculations to investigate the behavior of the hydrogen bond in δ-AlOOH under pressure. The highest OH-stretching A1 and B2 mode frequencies decrease under pressure leading to hydrogen bond symmetrization. After hydrogen bond symmetrization, the corresponding frequencies gradually increase. This softening and subsequent hardening of the OH bonds is a good spectroscopic indicator of hydrogen bond symmetrization and is observed in our GGA static calculations at ~30 GPa without considering tunneling effects. We have also carried out calculations of Raman peak intensities in several supercells with various hydrogen orderings to investigate the potential effect of H-disorder on the Raman spectrum of δ-AlOOH. Our results suggest that the four broad Raman bands observed experimentally in the range of OH-stretching mode frequencies could originate in H-disorder in this phase.
منابع مشابه
Vibrational, electronic and structural properties of wurtzite GaAs nanowires under hydrostatic pressure
The structural, vibrational, and electronic properties of GaAs nanowires have been studied in the metastable wurtzite phase via Resonant Raman spectroscopy and synchrotron X-ray diffraction measurements in diamond anvil cells under hydrostatic conditions between 0 and 23 GPa. The direct band gap E0 and the crystal field split-off gap E0 + Δ of wurtzite GaAs increase with pressure and their valu...
متن کاملFirst-principles study of pentaerythritol tetranitrate single crystals under high pressure: vibrational properties
First-principles theoretical methods were used to investigate the vibrational properties of pentaerythritol tetranitrate (PETN) under hydrostatic compression up to 4 GPa. Bond lengths and bond angles for the PETN molecules and the pressurevolume relation for the crystal under high pressure were calculated and compared with previous calculations and with experimental results. Based on the calcul...
متن کاملFabrication of Cellulose Nanofiber/AlOOH Aerogel for Flame Retardant and Thermal Insulation
Cellulose nanofiber/AlOOH aerogel for flame retardant and thermal insulation was successfully prepared through a hydrothermal method. Their flame retardant and thermal insulation properties were investigated. The morphology image of the cellulose nanofiber/AlOOH exhibited spherical AlOOH with an average diameter of 0.5 μm that was wrapped by cellulose nanofiber or adhered to them. Cellulose nan...
متن کاملA first-principles study of the vibrational properties of crystalline tetracene under pressure.
We present a comprehensive study of the hydrostatic pressure dependence of the vibrational properties of tetracene using periodic density-functional theory (DFT) within the local density approximation (LDA). Despite the lack of van der Waals dispersion forces in LDA we find good agreement with experiment and are able to assess the suitability of this approach for simulating conjugated organic m...
متن کاملساختار الکترونی123- Yدر فشار متعارف و فشارهای بالا
The electronic properties of YBa2Cu3O7-δ have been investigated by the energy-pseudopotential method within the local density approximation (LDA) with and without including generalized gradient corrections (GGC). The band structure, density of states and charge density of YBa2Cu3O7- have been calculated. The results are compared with other approaches such as LAPW, LCAO and LMTO for this syste...
متن کامل