研究目的
To investigate the effect of Li position and concentration on the physical properties of Li-doped ZnO using density functional theory and Boltzmann transport theory.
研究成果
The position and concentration of Li significantly affect the physical properties of ZnO. Li in interstitial sites (Lii) has lower formation energy and leads to n-type conductivity with decreasing band gap, while substitutional Li (LiZn) results in p-type conductivity with increasing band gap. Optimal electrical conductivity was found at 12.5% concentration for Lii model. The findings provide a theoretical basis for applications in optoelectronics, such as transparent conductive electrodes.
研究不足
The study is theoretical and based on computational models, which may not fully capture experimental complexities such as defects and impurities. The use of specific Hubbard parameters and approximations (GGA+U) might limit accuracy. Experimental validation is referenced but not performed in this work.
1：Experimental Design and Method Selection:
Density functional theory (DFT) with GGA+U method and Boltzmann transport theory were used. Calculations were performed using the Quantum Espresso package with Perdew-Burke-Ernzerhof (PBE) functional, ultrasoft pseudopotentials, and Hubbard parameters U(d, Zn)=10eV and U(p, O)=7eV. A 2x2x2 ZnO supercell with space group P63mc was employed.
2：Sample Selection and Data Sources:
A supercell containing 32 atoms (16 Zn and 16 O) was used. Li doping concentrations of 6.25%, 12.5%, and 18.75% were considered for both substitutional (LiZn) and interstitial (Lii) configurations.
3：25%, 5%, and 75% were considered for both substitutional (LiZn) and interstitial (Lii) configurations.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Computational software Quantum Espresso was used. No physical equipment or materials are specified as it is a theoretical study.
4：Experimental Procedures and Operational Workflow:
Structural optimization was done using the BFGS algorithm until forces were less than 10^-4 Ry/a.u. K-point sampling used a 4x4x4 Monkhorst-Pack grid. Self-consistent field convergence threshold was set at 10^-7 Ry. Energy cutoffs were 40 Ry for kinetic energy and 320 Ry for charge density.
5：Data Analysis Methods:
Formation energy, electronic structure, density of states, optical properties (dielectric function, absorption coefficient, transmittance), and electrical properties (conductivity, carrier concentration, mobility) were calculated. BoltzTrap code was used for electrical conductivity calculations with a rigid band approach.
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