研究目的
To investigate the phase transition pressure, electronic structure, optical properties, and stability of ZnSe and Cr2+:ZnSe with different doping concentrations under high pressure using first-principles calculations based on density-functional theory.
研究成果
The phase transition pressure decreases with increasing Cr2+ doping concentration, from 14.09 GPa for pure ZnSe to 9.07 GPa for 12.5% doped Cr2+:ZnSe. High pressure enhances the degeneracy of Cr-d orbitals and causes a blue-shift in absorption peaks, with wavelength shifts up to 268.2 nm. The structures remain stable under pressure as confirmed by defect formation energy and elastic constants. High pressure can be used to adjust material emission spectra.
研究不足
The study relies on computational methods which may have inherent approximations, such as the underestimation of band gaps in DFT. Experimental validation is not included, and the models assume periodic boundary conditions which might not fully capture real-world complexities.
1：Experimental Design and Method Selection:
First-principles calculations based on density-functional theory (DFT) using the projector augmented wave (PAW) method in the Vienna ab initio simulation package (VASP), with the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) functional. Phase transition pressure calculated via enthalpy-pressure relation.
2：Sample Selection and Data Sources:
Models created using 64-, 32-, and 16-atom ZnSe supercells with one Zn atom substituted by a Cr atom to achieve Cr2+ concentrations of
3：13%, 25%, and 5%. List of Experimental Equipment and Materials:
Computational software VASP; no physical equipment mentioned.
4：Experimental Procedures and Operational Workflow:
Optimization of structures, calculation of enthalpy, band structures, density of states, absorption coefficients, defect formation energy, and elastic constants under varying pressures.
5：Data Analysis Methods:
Analysis of enthalpy curves for phase transition pressure, examination of band structures and DOS for electronic properties, calculation of absorption coefficients using dielectric functions, and evaluation of stability through defect formation energy and Born stability criteria for elastic constants.
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