A DFT investigation of the role of oxygen vacancies on the structural, electronic and magnetic properties of ATiO3 (A = Mn, Fe, Ni) multiferroic materials

Unveiling oxygen vacancy impact on lizardite thermo and mechanical properties

Here, we performed a systematic DFT study assisted by the workflow framework SimStack for the mechanical and thermodynamic properties of the clay mineral lizardite in pristine and six different types of O vacancies configurations. In most cases, the defect caused a structural phase transition in the lizardite from the trigonal (pristine) to the triclinic phase. The results show that oxygen vacancies in lizardite significantly reduce the lattice thermal conductivity, accompanied by an elastic moduli reduction and an anisotropy index increase. Through the P-V relation, an increase in compressibility was evidenced for vacancy configurations. Except for the vacancy with the same crystalline structure as pristine lizardite, the sound velocities of the other vacancy configurations produce a decrease in these velocities, and it is essential to highlight high values for the Grüneisen parameter. We emphasize the great relevance of the punctual-defects introduction, such as O vacancies, in lizardite, since this microstructural design is responsible for the decrease of the lattice thermal conductivity in comparison with the pristine system by decreasing the heat transfer ability, turning lizardite into a promising candidate for thermoelectric materials.

First-Principles Study on Electronic, Magnetic, Optical, Mechanical, and Thermodynamic Properties of Semiconducting Gadolinium Phosphide in GGA, GGA+U, mBJ, GGA+SOC and GGA+SOC+U approaches

In the current article, the electronic, magnetic, and optical properties of GdP in the hypothetical zinc blende structure have been discussed by using GGA, GGA+U, mBJ, GGA+SOC, and GGA+SOC+U approaches. The energy vs volume plots in the three magnetic states suggest the ferromagnetic phase to be the stable phase of GdP. The cohesive energy calculated for GdP is negative, suggesting the stability of the compound. The electronic band structure calculations predict the binary GdP to be a direct bandgap conventional semiconductor. The optical properties confirm the semiconducting properties of GdP, and the bandgap formation follows Penn's criteria. The elastic constants also confirm the stability of the compound with ductile nature. The thermodynamic properties including Debye temperature, entropy, and specific heat capacity are studied under varying hydrostatic pressures taking into account the quasi-harmonic Debye model. The doping of Cu in the supercell of GdP results in the compound to exhibit half-metallic ferromagnetic properties. The magnetic moments calculated for Cu_xGd_1-xP (x = 0.25) are integer-valued backing its half-metallic character and fit excellent with the Slauter-Pauling rule Z_t-8. GdP in the zinc blende structure can prove a potential candidate for optoelectronic devices having better reflectivity in the UV region whereas its doped compounds have the potential to exhibit half-metallic properties useful in spintronics.

Surface and morphological studies of LiNbO3: p-type semiconductivity on stoichiometric surfaces

The surface and morphological properties of LiNbO3 surfaces were calculated, and particular semiconductor types for crystal morphologies were found.