研究目的
To study the structural, elastic, electronic and thermoelectric properties of Sr3MN (M = Sb, Bi) under pressure using density functional theory, focusing on their potential for thermoelectric device applications.
研究成果
The research demonstrates that Sr3MN (M = Sb, Bi) compounds undergo a brittle to ductile transition at 15 GPa, exhibit semiconducting behavior with reduced band gaps under pressure, and show promising thermoelectric properties with high Seebeck coefficients and reduced lattice thermal conductivity. The predicted figure of merit values indicate potential for thermoelectric applications, suggesting these materials could be used in devices converting waste heat to electricity. Future work could involve experimental synthesis and further optimization through doping or nanostructuring.
研究不足
The study is based on computational simulations and may not fully capture experimental conditions. The pressure range is limited to 15 GPa, and further experimental validation is needed. The use of specific functionals like PBE may underestimate bandgaps, and the inclusion of SOC is necessary for accurate results with heavier elements.
1：Experimental Design and Method Selection:
First-principles calculations based on density functional theory were employed, using the plane-wave pseudopotential method in CASTEP for geometry optimization and WIEN2k for electronic structure and elastic properties. The Tran-Blaha modified Becke-Johnson (TB-mBJ) potential was used for accurate bandgap calculations, and spin-orbit coupling (SOC) was included for heavier atoms. Transport properties were calculated using BoltzTraP, and lattice thermal conductivity was computed using Phono3py with the finite displacement approach.
2：Sample Selection and Data Sources:
The study focused on Sr3SbN and Sr3BiN compounds, with lattice parameters optimized and compared to available experimental and theoretical data.
3：List of Experimental Equipment and Materials:
Computational software packages including CASTEP, WIEN2k, BoltzTraP, and Phono3py were used. Specific parameters included a 21x21x21 Monkhorst-Pack k-point mesh, 500 eV cutoff energy, muffin tin radii of 2.3, 2.5, 2.3, and 2.2 Bohr for Sr, Sb, Bi, and N respectively, and RKmax of 8.
4：3, 5, 3, and 2 Bohr for Sr, Sb, Bi, and N respectively, and RKmax of Experimental Procedures and Operational Workflow:
5.
4. Experimental Procedures and Operational Workflow: Geometry optimization was performed under pressure using the BFGS algorithm. Elastic constants were calculated using IRelast. Electronic structures were computed with PBE and TB-mBJ potentials, with and without SOC. Transport coefficients were derived by solving the Boltzmann transport equation, and lattice thermal conductivity was calculated using a 21x21x21 q-mesh.
5：Data Analysis Methods:
Data were analyzed using standard equations for elastic moduli, hardness, and thermoelectric properties. Convergence criteria were set to 10^-4 Ry for energy and 0.001e for charges.
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