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Image, graphical abstract • Rare earth free permanent magnets can be realized in tetragonally distorted full Heusler alloys by light interstitial atoms. • Bain path calculations reveal that interstitials cause stable tetragonal distortion to full Heusler alloys. • The uniaxial anisotropy can be attributed to changes in the local crystalline environments around the interstitials. • We postulate that this provides a universal way to tailor the magnetic properties of prospective permanent magnets. Based on high-throughput density functional theory calculations, we investigated the effects of light interstitial H, B, C, and N atoms on the magnetic properties of cubic Heusler alloys, with the aim to design new rare-earth free permanent magnets. It is observed that the interstitial atoms induce significant tetragonal distortions, leading to 32 candidates with large (> 0.4 MJ/m3) uniaxial magneto-crystalline anisotropy energies (MAEs) and 10 cases with large in-plane MAEs. Detailed analysis following the perturbation theory and chemical bonding reveals the strong MAE originates from the local crystalline distortions and thus the changes of the chemical bonding around the interstitials. This provides a valuable way to tailor the MAEs to obtain competitive permanent magnets, filling the gap between high performance Sm-Co/Nd-Fe-B and widely used ferrite/AlNiCo materials. [ABSTRACT FROM AUTHOR]

The phase stability, electronic structure and transport properties of binary 3d, 4d and 5d transition metal silicides are investigated using high-throughput density functional calculations. An overall good agreement is found between the calculated 0 K phase diagrams and experiment. We introduce descriptors for the phase-stability and thermoelectric properties and hereby identify several candidates with potential for thermoelectric applications. This includes known thermoelectrics like Mn4Si7, β-FeSi2, Ru2Si3 and CrSi2 as well as new potentially meta-stable materials like Rh3Si5, Fe2Si3 and an orthorhombic CrSi2 phase. Analysis of the electronic structure shows that the gap formation in most of the semiconducting transition metal silicides can be understood with simple hybridization models. The transport properties of the Mn4Si7, Ru2Ge3 and Ir3Si5 structure types and the orthorhombic CrSi2 phase are discussed. The calculated transport properties are in good agreement with available experimental data. It is shown that a better thermoelectric performance may be achieved upon optimal doping. Finally, the high-throughput data are analysed and rationalized using a simple tight-binding model. [ABSTRACT FROM AUTHOR]

The interaction of tungsten hexacarbonyl [W(CO)6] precursor molecules with SiO2 substrates is investigated by means of density functional theory calculations with and without inclusion of long-range van der Waals interactions. We consider two different surface models, a fully hydroxylated and a partially hydroxylated SiO2 surface, corresponding to substrates under different experimental conditions. For the fully hydroxylated surface, we observe only a weak interaction between the precursor molecule and the substrate, with physisorption of W(CO)6. Inclusion of van der Waals corrections results in a stabilization of the molecules on this surface, but does not lead to significant changes in the chemical bonding. In contrast, we find a spontaneous dissociation of the precursor molecule on the partially hydroxylated SiO2 surface, where chemisorption of a W(CO)5 fragment is observed upon removal of one of the CO ligands from the precursor molecule. Irrespective of the hydroxylation, the precursor molecule prefers binding of more than one of its CO ligands. In light of these results, implications for the initial growth stage of tungsten nanodeposits on SiO2 in an electron-beam-induced deposition process are discussed. [ABSTRACT FROM AUTHOR]

We investigate the electronic and magnetic properties of the frustrated triangular-lattice antiferromagnets Cs2CuCl4 and Cs2CuBr4 in the framework of density functional theory. Analysis of the exchange couplings J and J' using the available x-ray structural data corroborates the values obtained from experimental results for Cs2CuBr4 but not for Cs2CuCl4. In order to understand this discrepancy, we perform a detailed study of the effect of structural optimization on the exchange couplings of Cs2CuCl4 employing different exchange-correlation functionals. We find that the exchange couplings depend on rather subtle details of the structural optimization and that only when the insulating state (mediated through spin polarization) is present in the structural optimization, we do have good agreement between the calculated and the experimentally determined exchange couplings. Finally, we discuss the effect of interlayer couplings as well as longer-ranged couplings in both systems. [ABSTRACT FROM AUTHOR]

Abstract: We report a critical analysis of the electronic structures and de Haas-van Alphen (dHvA) quantities of the heavy-fermion superconductors , , and . The ab initio calculated dHvA quantities are in good agreement with experimental data for and , when we adopt the delocalized LSDA description for the Ce 4f states. For , however, a better agreement with experiment is obtained when the Ce 4f electron is treated as a localized core electron. The implications for an emerging picture of the localization behavior of the 4f electron in these materials are discussed. [Copyright &y& Elsevier]

Abstract: The magnetic properties, lattice parameters and formation enthalpies of existing and hypothetical compounds (, La, Th, Mg, Ca and Sr) are calculated within the framework of density functional theory. In these compounds the magnetocrystalline anisotropy energy is dominated by itinerant Co 3d contributions. Band energy calculations suggest that—within in a rigid band picture—anisotropy energies of comparable size to those of hard magnetic materials containing rare earths could be obtained by hole doping of , e.g. by the substitution of Ca or Mg for Y. This idea is confirmed by the presented total energy calculations. However, the calculated enthalpies of formation suggest that and could only be prepared by non-equilibrium methods. [Copyright &y& Elsevier]

The electronic structure and magnetic properties of disordered FexPd100-x alloys (50

The dependence of the magnetic moments on the compositional order in Fe–Pt alloys was studied by neutron powder diffraction. For alloys with almost perfect L10-type long-range order the experimental value of the Fe magnetic moment was determined to be 2.8±0.1μB (extrapolated to zero temperature). Combined analysis of experimental and density functional data shows that the Fe moment drops with increasing Fe content, but is less sensitive to the degree of order, in contrast to the well-known behavior of Fe–Al alloys. [ABSTRACT FROM AUTHOR]

Abstract: In a recently presented X-ray magnetic circular dichroism (XMCD) study, the orbital/spin magnetic moment ratio of cobalt impurities inside gold host matrices has been determined and a large enhancement of the orbital moment for Co, compared with other dilute 3d-series metals has been observed. This means that a single cobalt atom deposited into bulk gold has a partially unquenched orbital moment. In the present work, the electronic structure of Co impurities inside gold has been calculated in the framework of local spin density approximation. The orbital and spin magnetic moment have been evaluated using the relativistic version of the full-potential local orbital minimum basis code. In agreement with experimental findings, the orbital moment is enhanced with respect to Co metal. On the other hand, lattice relaxation is found to reduce the orbital moment considerably, whereas the spin moment is less affected. [Copyright &y& Elsevier]

All‐d Heuslers are a category of novel compounds combining versatile functionalities such as caloric responses and spintronics with enhanced mechanical properties. Despite the promising transport properties (anomalous Hall (AHC) and anomalous Nernst (ANC) conductivities) shown in the conventional Co2XY Heuslers with p‐d hybridization, the all‐d Heuslers with only d‐d hybridization open a new horizon to search for new candidates with outstanding transport properties. In this work, the AHC and ANC are evaluated for thermodynamically stable ferro/ferri‐magnetic all‐d‐metal regular Heusler compounds based on high‐throughput first‐principles calculations. It is observed that quite a few materials exhibit giant AHCs and ANCs, such as cubic Re2TaMn with an AHC of 2011 S cm‐1, and tetragonal Pt2CrRh with an AHC of 1966 S cm‐1 and an ANC of 7.50 A m‐1K‐1. Comprehensive analysis on the electronic structure reveals that the high AHC can be attributed to the occurrence of the Weyl nodes or gapped nodal lines in the neighborhood of the Fermi level. The correlations between such transport properties and the number of valence electrons are also thoroughly investigated, which provides a practical guidance to tailor AHC and ANC via chemical doping for transverse thermoelectric applications. [ABSTRACT FROM AUTHOR]

Abstract: By applying density functional theory, we find strong evidence for an itinerant nature of magnetism in two families of iron pnictides. Furthermore, by employing dynamical mean field theory with continuous time quantum Monte Carlo as an impurity solver, we observe that the antiferromagnetic metal with small magnetic moment naturally arises out of coupling between unfrustrated and frustrated bands. Our results point to a possible scenario for magnetism in iron pnictides where magnetism originates from a strong instability at the momentum vector while it is reduced by quantum fluctuations due to the coupling between weakly and strongly frustrated bands. [Copyright &y& Elsevier]

In the CuII-p-hydroquinonate coordination polymer 1, the major pathway for antiferromagnetic exchange coupling runs along the hydroquinonate linker. Upon heating, 1looses its supporting DMF ligands in a two-step sequence; the antiferromagnetic CuII–CuIIinteraction in the final product 3is now mediated by two bridging oxygen atoms which results in an increase of the Jvalue by two orders of magnitude. [ABSTRACT FROM AUTHOR]

Magnetic shape memory (MSM) alloys, which transform martensitically below the Curie temperature in the ferromagnetic (FM) state, represent a new class of actuators. In Ni2MnGa, unusually large magnetic field-induced strains of about 10% have been observed. This effect is related to a high mobility of martensitic twin boundaries in connection with a large magneto-crystalline anisotropy. MSM materials exist in a variety of different martensitic structures depending on temperature and compositions. We investigate the energetics of L10 phase twin boundary motion quasi-statically with ab initio methods and relate the results to calculations of the magneto-crystalline anisotropy energy. Our results indicate that for the L10 structure the energy needed for a coherent shift of a twin boundary may be too large to be overcome solely by magnetic field-induced strains. [ABSTRACT FROM AUTHOR]

Electronic and transport properties of Bi2S3 with various dopants are studied using density functional theory and experimental characterizations. First, principle calculations of thermoelectric properties are used to evaluate the thermoelectric potential of the orthorhombic Bi2S3 structure. The computational screening of extrinsic defects is used to select the most favorable n-type dopants. Among all the dopants considered, hafnium and chlorine are identified as prospective dopants, whereas, e.g., germanium is found to be unfavorable. This is confirmed by experiment. Seebeck coefficient (S) and electrical conductivity (σ) measurements are performed at room temperature on pellets obtained by spark plasma sintering. An increase of power factors (S2·σ) from around 50 up to 500 μW K-2m-1 is observed for differently doped compounds. In several series of samples, we observed an optimum of power factor above 500 μW K-2m-1 at room temperature for a chlorine equivalence of 0.25 mol. % BiCl3. The obtained results are plotted on a semilogarithmic log (r) versus S graph to demonstrate that a very strong linear trend that limits the power factor around 500 μW K-2m-1 exists. Further improvement of Bi2S3 as thermoelectric material will require finding new doping modes that will break through the observed trend. The results of stability tests demonstrate that properties of optimally doped Bi2S3 are stable. [ABSTRACT FROM AUTHOR]

Ferromagnetic Fe 3 Sn, Fe 5 Sn 3 and Fe 3 Sn 2 single crystals were synthesized using the reactive flux technique. Derived from single crystal x-ray diffraction and Transmission Electron Microscopy (TEM), a new structural model is proposed for the Fe 5 Sn 3 crystals - the threefold twinning of an orthorhombic unit cell with (3 + 1) dimensional space group P bcm(α00)0s0. The spontaneous magnetization (M s) and the anisotropy constants K 1 and K 2 of Fe 3 Sn, Fe 5 Sn 3 and Fe 3 Sn 2 single crystals were determined in a wide temperature range using M(H) dependencies and a modified Sucksmith-Thompson technique. M s and K 1 were also evaluated in the framework of Density Functional Theory (DFT) and an overall good agreement was observed between the calculated and experimental results. Furthermore, a critical evaluation of different analytical models for the assessment of magnetocrystalline anisotropy was performed, which are restricted to the analysis of uniaxial magnetic domain patterns, and it is shown that such high-throughput techniques can lead to unrealistic results. Finally, a DFT high-throughput screening of the Fe-Sn phase diagram was used to identify Fe-Sn based phases with potential to be stabilized upon alloying, and their magnetization and magnetocrystalline anisotropy were evaluated. The results show that a similar strong anisotropy as observed in Fe 3 Sn may also be found in other Fe-Sn based phases, having higher potential to be used as hard magnetic material. Image 1 [ABSTRACT FROM AUTHOR]

Abstract The Co 2 B system shows a significant magnetovolume effect around its Curie temperature which makes it potentially attractive for magnetocaloric applications or thermomagnetic power generation, as a large coupling between the lattice and spin degrees of freedom is expected. We report on the synthesis of a series of Co 2-x Mn x B alloys and the investigation of their properties. The structural analysis indicates a single phase behavior up to x = 0.8 with no structural symmetry changes throughout the series. Measurements of both, macroscopic and local magnetic properties, reveal an anomalous behavior of the spontaneous magnetization, Curie temperature, and element-specific magnetic moments as a function of manganese concentration. The elemental contributions to the magnetization are analyzed using nuclear magnetic resonance (NMR) studies. Density functional theory (DFT) calculations guide us in the understanding of the origin of the observed anomaly, which is due to a complex magnetic coupling behavior between Mn atoms, which significantly affects the corresponding exchange interactions. The magnetocaloric properties of the Co 2-x Mn x B alloys show that the maximum entropy change peak temperature can be shifted between room temperature and 450 K upon variation of the manganese concentration without significant impact on the magnetocaloric response. The highest entropy change of −1.37 J k g − 1 K − 1 at 442 K is obtained for x = 0.1 for a field change of 2 T. This value is, however, quite low for any possible magnetocaloric or thermomagnetic power generation applications. Nevertheless, the good agreement between the advanced characterization and theory gives a deeper understanding of the Co 2-x Mn x B material system which can in the future be extended to other systems. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

[Display omitted] Half-antiperovskites (HAPs) are a class of materials consisting of stacked kagome lattices and thus host exotic magnetic and electronic states. We perform high-throughput calculations based on density functional theory (DFT) and atomistic spin dynamics (ASD) simulations to predict stable magnetic HAPs M 3 X 2 Z 2 (M = Cr, Mn, Fe, Co, and Ni; X is one of the elements from Li to Bi except noble gases and 4 f rare-earth metals; Z = S, Se, and Te), with both thermodynamical and mechanical stabilities evaluated. Additionally, the magnetic ground states are obtained by utilizing DFT calculations combined with the ASD simulations. The existing spin frustration in an AFM kagome lattice manifests as competing behavior of the in-plane FM and AFM couplings. For a total number of 930 HAP compositions considered, we have found 23 compounds that are stabilized at non-collinear antiferromagnetic (AFM) state and 11 compounds that possess ferromagnetic (FM) order. [ABSTRACT FROM AUTHOR]

Copper sulfides and copper selenides have recently been reported as new and promising low-cost and environmentally friendly thermoelectric materials. Here, it is shown that these materials have actually been studied for more than 190 years and the absence of commercial thermoelectric modules based on them stems from some major intrinsic issues related to these chalcogenides. Further development of these semiconductors will require addressing and solving these problems before large scale utilization can be considered. [ABSTRACT FROM AUTHOR]

Abstract: We present a detailed study of the derivation of the Hubbard model parameters for in the framework of ab initio Density Functional Theory. We show that calculations with different (i) wavefunction basis, (ii) exchange correlation functionals and (iii) tight-binding models provide a reliable benchmark for the parameter values. We compare our results with available extended Hückel molecular orbital calculations and discuss its implications for the description of the properties of . The electronic properties of are also briefly discussed. [Copyright &y& Elsevier]

Abstract: HoNi2B2C single crystals prepared by the floating zone method were investigated by resistivity, magnetization, specific heat and point-contact measurements. The coexistence of superconductivity (SC) and antiferromagnetism (AFM) in HoNi2B2C is considered experimentally and theoretically for commensurate (C), incommensurate (IC) and metamagnetic magnetic structures within the multiband picture of Fermi surface sheets (FSS) obtained within full potential FPLO–LDA calculations. Special attention is paid to the admixture of Ho 5d states which mediate the pair breaking exchange between the Ho 4f derived local moments and the conduction electrons bearing the superconductivity. Within the paramagnetic and the uniform IC spiral phases, anisotropic multiband SC coexists with magnetism. Within the C-phase (below T N =5.3K) single band isotropic SC survives at a single FSS free of Ho 5d states in accord with isotropic standard WHH shaped upper critical fields H c2(T). The superconducting energy gap obtained from point-contact data was found to disappear at a slightly higher temperature T ∗ =5.6K which is also observed in specific heat measurements. Using the experimental values for the energy gap Δ(0) and H c2(0) at zero temperature, the characteristic phonon frequency, the electron–phonon coupling constant and the Fermi velocity of the residual superconducting phase were estimated from the standard isotropic single band model. [Copyright &y& Elsevier]

The electronic structure of the LaPtSn compound was studied both experimentally and theoretically. A sample of LaPtSn was prepared and powder X-ray diffraction measurements were performed showing that LaPtSn crystallizes in the orthorhombic space group Pnma with the structure type TiNiSi. Specific heat data were measured and analyzed and the electronic and phonon contributions were derived. Electronic structure calculations were performed using the full-potential non-orthogonal local-orbital minimum-basis band structure scheme and the general potential linearized augmented plane wave method in the framework of density functional theory. We studied the electronic density of states (DOS), the charge density distribution and the performance of local density approximation and generalized gradient approximation with respect to the equilibrium volume of LaPtSn. A rather low value of the mass enhancement coefficient λ is derived from comparison of the calculated DOS at the Fermi level and the experimental value of the γ coefficient of specific heat. Implications for the electronic properties of the Kondo lattice compound CePtSn are discussed. [Copyright &y& Elsevier]