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Pressure-induced phase transitions, electronic, elastic and vibrational properties of zinc oxide under high pressure
摘要： In this work, the crystal structure of the ZnO was studied under high hydrostatic pressure using ab initio calculations. Pressure–volume relationships and structural transitions in ZnO were investigated using Siesta method. A first-order transition from the hexagonal wurtzite (B4) structure with space group P63mc to the cubic NaCl (B1) structure with space group Fm(cid:2)3m was successfully observed. A transition was also observed from Fm(cid:2)3m to another cubic CsCl (B2) structure with space group Pm(cid:2)3m for ZnO. These phase transitions which occur around 9 and 119.5 GPa were also analyzed from the total energy and enthalpy calculations. In addition, electronic, elastic and vibrational properties of ZnO were analyzed based on the high pressure.
关键词： Bulk crystals,Electronic structure calculations,Pressure,Phase transitions
更新于2025-09-23 15:22:29
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: From quantum dots to bulk crystals and additional boundary conditions for Rydberg exciton-polaritons
摘要： We propose schemes for calculation of optical functions of a semiconductor with Rydberg excitons for a wide interval of dimensions. We have started with a zero-dimensional structure (quantum dot), then going to one-dimensional (quantum wire), two-dimensional (quantum wells and wide quantum wells), and ?nally three-dimensional bulk crystals; our analytical ?ndings are illustrated numerically, showing an agreement with available experimental data. Calculations including exciton-polaritons are performed; the case of a large number of polariton branches is discussed, and obtained theoretical absorption spectra show good agreement with experimental data.
关键词： quantum wells,bulk crystals,exciton-polaritons,quantum wires,Rydberg excitons,quantum dots
更新于2025-09-23 15:21:01
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Effects of Te additions and stirring in the In segregation in Ga1-xInxSb alloys
摘要： The influence of tellurium in the indium segregation of Ga1-xInxSb:Te ingots obtained by the conventional vertical Bridgman method (CVBM), under stirred and non-stirred conditions, was investigated. Three Te-doped ingots and three no-doped ingots were unidirectionally solidified at a constant speed of 2.0 mm/hour, inside quartz ampoules, closed under argon, and with a conical tip. The furnace temperature was set for overheating between 73.5 – 93°C, and temperature gradients between 3.0 – 3.3°C/mm. The tellurium doped ingots showed a smaller number of grains and no cracks in the middle region of the ingots, right after the tip, in comparison with the no-doped ingots. Moreover, when comparing the stirred with the non-stirred ingots, the EDS experimental profile of indium in Te-doped synthetized without melt stirring ingot showed a better agreement with the Scheil–Gulliver equation than the stirred Te-doped ingots. The Te-doped ingots when stirring the melt during synthesis showed a more constant axial indium distribution, up to 85% of their lengths. The constant lattice estimated from TEM diffraction images are respectively 6.29 ? for the non-doped sample and 6.17 ? for the Te-doped sample. A qualitative account for the increase of the lattice parameter and the Hall measurements results is that the tellurium compensates for the native acceptor defects, contributing to the microstructural quality in the Ga1-xInxSb ingots.
关键词： vertical Bridgman,GaInSb,compound semiconductor III-V,tellurium,bulk crystals
更新于2025-09-09 09:28:46