We performed a systematic full-potential density functional theory study with the generalized gradient and local density $\text{approximation}+U$ approaches on five possible $(1\times 1)$ terminations of the low-index polar (111) surface of ${\mathrm{Fe}}_3{\mathrm{O}}_4$. Applying the concepts of first-principles thermodynamics, we analyze the composition, the structure, and the stability of the ${\mathrm{Fe}}_3{\mathrm{O}}_4$ (111) orientation at equilibrium with an arbitrary oxygen environment. The densities of states of the unrelaxed and relaxed ${\mathrm{Fe}}_3{\mathrm{O}}_4$ (111) surfaces were calculated and compared with that of bulk ${\mathrm{Fe}}_3{\mathrm{O}}_4$. The calculations reveal that the ${\mathrm{Fe}}_{\mathrm{oct}2}\text{−}{\mathrm{Fe}}_{\mathrm{tet}1}\text{−}\mathrm{O}1$-terminated surface is energetically favored, showing metallic properties. The ${\mathrm{Fe}}_{\mathrm{oct}1}\text{−}\mathrm{O}2$-terminated surface is more active than the other two Fe-terminated surfaces, showing half-metallic properties, similar to bulk ${\mathrm{Fe}}_3{\mathrm{O}}_4$. The ${\mathrm{Fe}}_{\mathrm{tet}1}\text{−}\mathrm{O}1$-terminated surface, the O-terminated surfaces, and the surfaces with vacancy defects all show metallic properties.

Thermal spin transport properties of graphene and hexagonal boron nitride nanoribbon heterojunctions have been investigated using density functional theory calculations combined with the Keldysh nonequilibrium Green's function approach.

On the basis of the density functional theory combined with the Keldysh nonequilibrium Green’s function method, we investigate the spin-dependent transport properties of single-edge phosphorus-doped ZGNR systems with different widths. The results show a perfect spin filtering effect reaching 100% at a wide bias range in both parallel (P) and antiparallel (AP) spin configurations for all systems, especially for 6-ZGNR-P system. Instructively, for the AP spin configuration, the spin down current of the 4-ZGNR-P system exhibits a negative differential effect. By analyzing the transmission spectrum and the spin-resolved band structures of the electrodes, we elucidate the mechanism for these peculiar properties. Our findings provide a new way to produce multifunctional spintronic devices based on phosphorus-doped zigzag graphene nanoribbons.

The thermal transport properties of an iron-doped molybdenum disulfide system were explored theoretically using the density functional theory calculations combined with the Keldysh non-equilibrium Green's function approach.

Thermoelectric transport properties of Ti doped or adsorbed monolayer blue phosphorene are investigated by density functional theory combined with the nonequilibrium Green’s function formalism. The thermal giant magnetoresistance and a nearly 100% spin polarization which solely relies on the temperature gradient of electrodes without bias or gate voltage are observed. Moreover, the spin Seebeck effect is also found. Furthermore, taking into account the electronic and phonon dispersion, the thermoelectric merit for Ti doping in the monolayer blue phosphorene at room temperature is also studied, the maximum value of thermoelectric merit can reach 1.01 near the Fermi level. The results indicate that Ti doped or adsorbed monolayer blue phosphorene has potential application in both spintronics and spin caloritronics.