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Zintl materials have received enormous attention in recent time due to their unique structure and thermoelectric efficiency. In this work, quaternary Zintl compounds LaAgZnX2 (X = P, As) have been comprehensively investigated using the FP-LAPW + lo method through first principles approximation. The dynamic stability of the samples is performed through phonon analysis. Birch–Murnaghan equation of states is used to determine ground state parameters. The lattice constant increases while formation energy and bulk modulus B(GPa) decrease by anion replacement from P to As. Band structure calculation shows that LaAgZnP2 is an indirect bandgap semiconductor while LaAgZnAs2 is a direct bandgap semiconductor. The density of states (DOS) demonstrates that the valence band (V.B) is mainly comprised of Zn-d and X-p states while the La-f state is in the conduction band (C.B) along with the minor contribution of the La-d state. Substantial absorption is observed in the low-frequency ultraviolet and visible spectrums for these compounds. Red shifting of the hallmark optic peak occurs due to the anion replacement from P to As. To investigate the electric and thermal conductivities, Seebeck coefficients, and thermopower factor, the Boltzmann transport theory is used to quantify them for these materials. High absorption peaks and figures of merits of these compounds highlight their potential usage in optoelectronics and thermoelectric systems. [ABSTRACT FROM AUTHOR]

First-principles calculations based on density-functional theory have been used to investigate the effect of biaxial strain and oxygen vacancy on the electronic, photocatalytic, and electrocatalytic properties of PbTiO3 oxide. Our results show that PbTiO3 has a high exciton binding energy and a band gap that can be easily moderated with different strain regimes. From a reactivity viewpoint, the highly exothermic adsorption of hydrogen atoms in both pristine and strained PbTiO3 structures does not make it a potential electrocatalyst for the hydrogen evolution reaction. Fortunately, the presence of oxygen vacancies on the PbTiO3 surface induces moderate adsorption energies, making the reduced PbTiO3 suitable for hydrogen evolution reaction processes. [ABSTRACT FROM AUTHOR]

ab initio calculations were performed for the cubic perovskites Borides XRh3B, (X=Dy, Ho, Er). In this work, we have used the augmented plane-wave plus local orbital method to compute the equilibrium structural parameters and electronic structure of densities of states, as well as for the first time, prediction of the thermo-elastic properties of these crystals are presented. The chemical bonding of these compounds has been investigated by using of topological analyses grounded in the theory of atoms in molecules (AIM). All of the electron density critical points in the unit cell were systematically calculated in order to calculate basins interaction of each atoms and give exact classification of the bonding character.

The structural, elastic, electronic and magnetic properties of quaternary OsCrMnSb and IrCrMnSb Heusler alloys are performed employing ab initio electronic structure calculations. It has been identified that the YI type is the most stable structure among the three configurations for both OsCrMnSb and IrCrMnSb alloys in the magnetic state. The calculated cubic elastic constants show that these alloys fulfill the mechanical stability criteria. The band structures and density of state calculations reveal the half-metallic (HM) behavior of these alloys with a direct gap, and the half-metallicity is rather originated from the Cr-d states. Results on magnetic properties suggest that OsCrMnSb and IrCrMnSb are HM antiferromagnets. However, the inclusion of spin–orbit coupling affects strongly the IrCrMnSb alloy, losing its HM nature. [ABSTRACT FROM AUTHOR]

The topology of the electron density for congruent melting oxyborate Bi2ZnOB2O6 and CaBi2B2O7 is studied in light of the theory of atoms in molecules. All the electron density critical points in the unit cell are systematically calculated. What makes these compounds most interesting is a rich collection of B-O long-distance bond paths. We focus on the study of the asymmetric bonds and basins forming the anisotropic B2O5 groups in these compounds. B2O5 shows transferable contributions to the crystal, with long bond paths. We relate these observations to the strong behavior, which favorites its application to the second harmonic generation field. Wherefore, the analyses of bonding and related optical properties as well as the multipole moments of the CaBi2B2O7 compounds are predicted for the first time. CaBi2B2O7 exhibits some uniaxial dielectric anisotropy resulting in a strong birefringence. We also report calculations of the complex second-order optical susceptibility dispersion for the principal tensor components and evaluate their intra-and inter-band contributions. [ABSTRACT FROM AUTHOR]

We have carried out a computational study of the behavior under pressure of three polymorphs of MgInS. Ab initio calculations are performed to determine the equation of state parameters of direct (DS) and inverse (IS) spinel phases, and a defect-LiTiO-type (LTO) structure observed at high pressure. It has been shown that the DS phase has higher enthalpy at zero pressure than the IS one, and the latter undergoes a pressure-induced transition to the LTO structure at 8 GPa, very close to the experimental value. Additionally, the topological analysis of the electron density of this IS phase indicates that the size and atomic-like bulk modulus associated with the sulfur atom are the key contributions to of the IS phase of MgInS. This result is in concordance with the anomalous trend found for at spinels (, S, Se) as X increases its atomic number. [ABSTRACT FROM AUTHOR]