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We investigated the magnetic alignment and formation energy of Niobium (Nb) in magnetite using density functional theory (DFT) calculations with both GGA + U and meta-GGA approaches. Our findings revealed that Nb exhibits greater stability when located at the octahedral site within the compound, although it remains metastable overall. By analyzing the deviation of the Nb-O bond from its expected ionic behavior, we have gained valuable insights into how Nb influences the magnetic moment in Nb-doped magnetite, which was determined to be 3.275 μ B /f.u. Moreover, examination of the bond angles has provided further justification for the observed reduction in this magnetic moment compared to pristine magnetite, where it is ∼ 4.0 μ B /f.u. This study yields significant insights into doped magnetite, a crucial industrial compound. • The stability and magnetism of niobium-doped magnetite are investigated. • Density functional theory based on GGA+ U and Meta-GGA functionals was used. • Nb dopant is more stable when substituting a Fe at the octahedral site. • Nb doping decreases the saturation magnetization of magnetite. • Nb-doped Fe 3 O 4 is metastable, while NbFe 2 0 4 constitutes the ground state. [ABSTRACT FROM AUTHOR]

Despite significant advances in first-principles calculation methods, there is no single exchange-correlation functional which predicts the ground state of materials without an error yet. We investigated how accurately ground states of binary semiconductors are described using 16 exchange-correlation functionals (with or without van der Waals corrections). LDA, PBEsol, SCAN (with or without rVV10 correction), and PBE with D3 van der Waals correction (zero or Becke-Johnson damping) show good predicting power. The lattice constants of stable phases were slightly better described by SCAN, PBEsol, PBE+D3 (Becke-Johnson damping), and MS2. We also propose a set of functionals to double-check the stability of new materials based on the majority vote. [ABSTRACT FROM AUTHOR]

The 9R phase model based on experimental orientation relationship are constructed, the mechanical moduli of the face-centered cubic (FCC) and 9R phases in CrCoNi medium-entropy alloy (MEA) are investigated by first-principles calculations with the meta-generalized gradient approximation (meta-GGA) functional. This functional accurately describes CrCoNi MEA, captures localized electronic states, and overcomes the challenge of DFT + U parameters in special quasi-random structure (SQS) based transition metal atom models. Results indicate that the 9R phase exhibits higher mechanical moduli than the FCC phase, with a 12% increase in bulk modulus and a 7% increase in Poisson's ratio. Consequently, the strength and toughness of CrCoNi MEA are significantly enhanced. Doping Mo, Ta, and W in the MEA structures improves strength by promoting the formation of the 9R phase compared to the doped single FCC phase. Calculations of the work of adhesion and fracture toughness for the 9R/FCC interface reveal improved interface properties with Mo and W doping. These enhancements are attributed to the hybridization of electronic orbitals in the doped CrCoNi MEA, resulting in changes in bond types between neighboring atoms and subsequent modifications of mechanical properties in the 9R phase. Comparative computational values strongly support an alloy design strategy involving Mo doping and the construction of the 9R phase to achieve superior mechanical properties in MEA. [Display omitted] • The GSFE from Meta-GGA showed trends akin to GGA calculations, but distinct values. • The formation of the 9R phase was explored through pioneering computational insights. • Doping effect on the interface toughness of the 9R phase of CrCoNi MEA was studied. [ABSTRACT FROM AUTHOR]

Highlights • The band gap and effective masses are highly dependent on NW diameter and orientation. • Strain particularly affect effective masses of the 1 × 1 nm2 [1 1 1]-oriented NWs. • Strain engineering can improve device characteristics in InAs nanowires. • Controlling process induced strain is critical for uniform device characteristics. Abstract The impact of uni-axial compressive and tensile strain and diameter on the electronic band structure of indium arsenide (InAs) nanowires (NWs) is investigated using first principles calculations. Effective masses and band gaps are extracted from the electronic structure for relaxed and strained nanowires. Material properties are extracted and applied to determine charge transport through the NWs described within the effective mass approximation and by applying the non-equilibrium Green’s function method. The transport calculations self-consistently solve the Schrödinger equation with open boundary conditions and Poisson’s equation for the electrostatics. The device structure corresponds to a metal oxide semiconductor field effect transistor (MOSFET) with an InAs NW channel in a gate-all-around geometry. The channel cross sections are for highly scaled devices within a range of 3 × 3–1 × 1 nm2. Strain effects on the band structures and electrical performance are evaluated for different NW orientations and diameters by quantifying subthreshold swing and ON/OFF current ratio. Our results reveal for InAs NW transistors with critical dimensions of a few nanometer, the crystallographic orientation and quantum confinement effects dominate device behavior, nonetheless strain effects must be included to provide accurate predictions of transistor performance. [ABSTRACT FROM AUTHOR]

• Multiple DFT methods were evaluated for the simulation of metal-supported metal nanoislands. • Triatomic clusters of Pt on Au(111) are more stable with a linear conformation while those of Pd are more stable with a triangular conformation. • Pt and Pd clusters with four or more atoms on Au(111) prefer non-linear conformation. • The various DFT methods yield different energy for the adsoriton of hydrogen on Pt and Pd nanoislands on Au. We have evaluated various density functional theory (DFT) methods to simulate geometric, energetic, electronic, and hydrogen adsorption properties of metal-nanoparticles supported on metal surfaces. We used Pt and Pd nanoislands on Au(111) as model systems. The evaluated DFT methods include GGA (PW91, PBE, RPBE, revPBE, and PBESol), GGA with van der Waals (vdW) corrected (PBE-D3), GGA with optimized vdW functionals (revPBE-vdW), meta-GGA (SCAN and MS2), and the machine learning-based method BEEF-vdW. The results show that the various DFT methods yield similar geometric and electronic properties for Pt (or Pd) nanoislands on Au(111). The DFT methods also produce similar relative energetics for small Pt (or Pd) clusters with different conformations on Au(111). The results show that a triatomic cluster of Pt on Au(111) is more stable with a linear conformation. In contrast, a triatomic cluster of Pd is more stable with a triangular conformation. For clusters with four or more atoms, Pt and Pd clusters on Au(111) prefer non-linear conformation. We found that the various DFT methods yield different results only for the adsorption energy of hydrogen. [Display omitted] [ABSTRACT FROM AUTHOR]

• Adsorption characteristics of NH 3 , NO, NO 2 , CO and CO 2 molecules on a black phosphorene are explored using state-of-the-art computational DFT methods. • All molecules are shown to adsorb on the phosphorene surface with different favorite adsorption sites, depending on the molecule geometry and orientation. • At high coverages, the calculated adsorption energies per molecule show that the molecule-molecule interactions for the SCAN+rVV10 is stronger than that for the optB88-vdW functional showing new insights for the role of meta-GGA. Using Density Functional Theory (DFT), we perform a detailed computational study to explore the adsorption behaviors of NH 3 , NO, NO 2 , CO and CO 2 gas molecules on a black phosphorene surface at several coverages. Van der Waals (vdW) interactions were taken into account within the optB88-vdW functional. In addition, a comparison with the strongly-constrained and appropriately-normed (SCAN) meta-generalized gradient approximation (meta-GGA) is discussed. Our calculations show that all molecules adsorb on the surface of black phosphorene with different favorable adsorption sites, depending on the molecule's geometry and orientation. Alongside the adsorption energies, other properties are presented including the adsorption distances and charge transfers. At high coverages, the adsorption energies per molecule show that the functionals start to behave differently as the coverage rate increases. The significant charge transfer between NO and NO 2 molecules and black phosphorene suggests its potential integration towards efficient nitrogen-oxide detectors. [Display omitted] [ABSTRACT FROM AUTHOR]

Electronic structure of Ta-doped cubic (bixbyite-type) lutetium oxide was analyzed using augmented plane wave with local orbitals density functional theory (DFT) calculations with meta-generalized gradient approximation (meta -GGA, mGGA) Räsänen, Pittalis and Proetto functional. Two doping sites, three oxidation states of the dopant and optional interstitial oxygen (O i) were considered. The calculations indicate that introduction of the dopant results in energy levels below conduction band, with strong contribution of Ta 5 d orbitals. The position of the levels depends strongly on the oxidation state of the dopant. Depending on the composition, two distinct electron traps with depths of 1.5–1.2 eV and 0.9–0.2 eV were revealed. Introduction of O i at proximity of the Ta dopant results in partial overlap of the Ta-related defect states with conduction band, which makes the traps very shallow, deteriorating the electron trapping properties. In some cases, shallow hole traps can also be attributed to the O i. The calculated traps structure is in good accord with the experimental data. Image 1 • Ta-doped cubic (bixbyite-type) lutetium oxide was analyzed using FP-LAPW/mGGA DFT calculations. • Two doping sites, three oxidation states of the dopant and optional interstitial oxygen were considered. • Two distinct electron traps (related to Ta 5 d orbitals) with depths of 1.5–1.2 eV and 0.9–0.2 eV were revealed. • Introduction of interstitial oxygen at proximity of the Ta dopant deteriorates the electron trapping properties. • The calculated traps structure is in good accord with experimental data. [ABSTRACT FROM AUTHOR]