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• The band structure of NpB 2 under the influence of U parameter and spin–orbit coupling (SOC) effects is discussed in detail. • The magnetic origin of NpB 2 is confirmed by electron localization function (ELF) and spin magnetic moment. • The Critical temperature (T C) of NpB 2 is obtained by Monte Carlo simulations and the regulation of ferromagnetic phase transition is realized. • The magnetocrystalline anisotropy energy (MAE) of NpB 2 are calculated and the contributions of different orbitals to SOC are provided. The electronic structure and magnetic properties of strongly-correlated compound neptunium boride (NpB 2) were investigated by first-principles calculation together with Monte Carlo simulations. Our results showed that NpB 2 can exist stably in terms of mechanical stability and thermodynamic stability. From the band structure and spin magnetic moment, it can be judged that the material exhibits obvious metallic properties, and the magnetism is mainly caused by the 5 f orbitals of Np. We also provide a more detailed distribution of electrons by electron localization function. Through Monte Carlo simulation, we not only obtain the magnetic moment and magnetic susceptibility of NpB 2 at different temperatures, but also found the competitive relationship between the crystal field (D) and magnetic field (h) in affecting the magnetothermal properties, where the critical temperature (T C = 116 K) is in good agreement with the experimental data. In addition, the magnetocrystalline anisotropy energy of NpB 2 is calculated and the contributions of different orbitals to spin–orbit coupling (SOC) effect are provided. For relatively complex f orbitals, f x 3 and f y 3 x 2 orbitals are coupled to the greatest degree in the direction of the inner layer, while other f orbitals (such as f z x 2 and f y 3 x 2 , f y z 2 and f z x 2 , f x z 2 and f z 3 ) show a considerable degree of coupling outside the plane. Our work not only helps to understand the internal physical mechanism of NpB 2 , but also helps to explore the potential applications of such magnetic materials. [ABSTRACT FROM AUTHOR]

We have conducted a study on the electronic and thermoelectric characteristics of Janus AsSeX (X = Cl, Br, I) monolayers. To accomplish this, we employed a combination of density functional theory (DFT) and Boltzmann transport theory. Through our study, we observed that the Janus AsSeX monolayers possess excellent dynamic, thermal, and mechanical stabilities. Our results reveal that AsSeCl, AsSeBr, and AsSeI are indirect band gap semiconductors with bandgaps of 2.10 eV, 1.87 eV, and 1.85 eV, respectively. Following the value of the B/G and v , we observe that Janus AsSeCl displays brittle property, whereas Janus AsSeBr and AsSeI exhibit ductile characteristics. We have also calculated the lattice thermal conductivity of these materials at room temperature, which are 1.87 Wm−1K−1, 3.80 Wm−1K−1, and 2.63 Wm−1K−1 for AsSeCl, AsSeBr and AsSeI, respectively. Furthermore, we have extracted thermal transport parameters, including the phase volume space group velocity, scattering rate, Grüneisen parameter, and group velocity, and carried out an in-depth analysis of their underlying mechanisms. Finally, we predict ZT values of 1.55, 0.95, and 1.11 for the p-type doping of Janus AsSeCl, AsSeBr, and AsSeI monolayers at 700 K, indicating that Janus AsSeCl and AsSeI monolayers are potential thermoelectric materials with high ZT values. [ABSTRACT FROM AUTHOR]

We systematically investigate the effect of strain engineering on the thermodynamic stability, electronic structure, Seebeck coefficient and other properties of two-dimensional (2D) MgI 2 monolayer on the basis of first-principles. The increasing stress causes the maximum phonon frequency of the MgI 2 monolayer to decrease gradually. With the increase of tensile strain, although the indirect-band structure remains the same from the Perdew-Burke-Eruzerhof (PBE) and Heyd-Scuseria-Ernzerhof (HSE06) levels with considering the spin-orbital coupling, the peaks of conduction band and valence band are closer of the MgI 2 monolayer. In the process of tensile strain from 2% to 4%, the number of band valleys increases, and the multiple valley pockets caused by such strain increase the Seebeck coefficient. It is found that the Seebeck coefficient increased from 140.86 μV/K without strain to 231.58 μV/K under 4% tensile strain. It also makes the power factor reach its peak at 4% strain of the MgI 2 monolayer. However, the lattice thermal conductivity of the MgI 2 monolayer is 0.89 W/mK at 300 K in the case of no strain, and it decreases linearly with the increase of tensile strain. The results showed that the ZT value increased gradually with the increasing tensile strain, and it reaches 1.39 at 300 K for the MgI 2 monolayer under the 9% tensile strain. Greatly stimulated further theoretical and experimental research on strain engineering and wish to improve thermoelectric conversion efficiency of two-dimensional (2D) materials. [ABSTRACT FROM AUTHOR]

• We study the lattice thermal conductivity, scattering rate, and group velocity of SrO for the first time. • We study the effect of pressure on thermoelectric properties of SrO for the first time. • The thermoelectric properties of the B1 phase SrO behave best at zero pressure. We studied the electronic structure and thermoelectric properties of SrO under pressure via first-principle calculations. The obtained phase transition pressure of SrO from B1 phase to B2 phase is 37 GPa at room temperature. At Gamma point, the phonon largest peak frequencies of SrO are 14.6 THz (B1 phase) and 18.9 THz (B2 phase), in addition, the LO-TO splitting frequencies are 8.6 THz (B1 phase) and 8.21 THz (B2 phase) under 0 GPa for B1 phase and 64 GPa for B2 phase, respectively. The B1 phase of SrO has an indirect band gap (3.31 eV) at 0 GPa, while the B2 phase has a smaller direct band gap (2.27 eV) at 70 GPa. At 0 GPa, the born effective charges of SrO are 2.44 (B1 phase) and 2.60 (B2 phase), and the dielectric constants are 3.80 (B1 phase) and 4.47 (B2 phase). When the temperature reaches 700 K and the carrier density reaches 1.2 × 10 21 cm−3, the ZT value of B1 phase reaches 0.61 at 0 GPa. By comparison, we found that the thermoelectric properties of the B1 phase behave better than those of the B2 phase at zero pressure. [ABSTRACT FROM AUTHOR]