This paper undertakes a comprehensive examination of the electronic and topological properties of triclinic enantiomorphic $\mathrm{Nb}{\mathrm{P}}_x{\mathrm{As}}_{1-x}$ alloys ($x$ $=0$, 0.25, 0.50, 0.75, 1) belonging to the space group $P1$, through first-principles and Wannier-based tight-binding analyses. Our paper reveals band inversion coupled with a distinctive fourfold band crossing near the Fermi energy, attributed to hybridization among Nb-$d$ orbitals. Intriguingly, $\mathrm{Nb}{\mathrm{P}}_x{\mathrm{As}}_{1-x}$ alloys exhibit nontrivial topological features even without spin-orbit coupling (SOC), primarily due to band inversion. Upon incorporating SOC, the fourfold band crossings transition into gapped bands, bifurcating into pairs of Weyl points with distinct chiralities. These Weyl points possess linear dispersion, categorizing the alloys as type-I topological Weyl semimetals. Additionally, SOC induces the emergence of Fermi arcs in the (111) surface states of the first Brillouin zone, connecting Weyl points of opposite chiralities. The findings establish $\mathrm{Nb}{\mathrm{P}}_x{\mathrm{As}}_{1-x}$ alloys as promising candidates for applications in topological materials, while enriching the understanding of topological phases and their correlations with electronic structure.

New ${}^{53}\mathrm{Cr}$ solid-state NMR measurements are presented for ${\mathrm{Cr}}_2\mathrm{N},$ ${\mathrm{CrB}}_2,$ ${\mathrm{CrO}}_2,$ ${\mathrm{Cr}}_2{\mathrm{O}}_3,$ ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{CrO}}_4,$ and ${\mathrm{BaCrO}}_4$. Measurements of the ${}^{53}\mathrm{Cr}$ nuclear quadrupole coupling constants, asymmetry parameters, and chemical (Knight) shifts of chromium compounds provide important experimental data for the validation of quantum chemistry calculations. In this work, natural abundance ${}^{53}\mathrm{Cr}$ magnetic resonance, at 9.4 T, is used to examine the metals ${\mathrm{Cr}}_2\mathrm{N}$ and ${\mathrm{CrB}}_2$ as well as the diamagnetic insulating chromates ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{CrO}}_4$ and ${\mathrm{BaCrO}}_4$ at room temperature. ${}^{14}\mathrm{N}$ and ${}^{11}\mathrm{B}$ NMR spectra are also obtained at room temperature for ${\mathrm{Cr}}_2\mathrm{N}$ and ${\mathrm{CrB}}_2,$ respectively. The shift observed from ${\mathrm{CrB}}_2$ is believed to be the largest Cr(0) Knight shift (−9982 ppm) for any chromium-containing metallic material. ${}^{53}\mathrm{Cr}$ measurements in zero applied magnetic field as a function of temperature are reported for ferromagnetic ${\mathrm{CrO}}_2$ and antiferromagnetic ${\mathrm{Cr}}_2{\mathrm{O}}_3$. Within experimental accuracy the magnetization behavior in ${\mathrm{CrO}}_2$ is modeled using Bloch spin-wave theory, where the magnetization decreases as $T^{3/2}$ over temperatures from 4.2 to 295 K, which also appears to adequately model the sublattice magnetization of ${\mathrm{Cr}}_2{\mathrm{O}}_3$. These new experimental results are put into the context of previous magnetic resonance results found in the literature by providing the first comprehensive tabulation of such ${}^{53}\mathrm{Cr}$ magnetic resonance data from solids for over 50 years. The low-temperature zero applied magnetic field central frequencies are correlated with valence state, and spin stiffness has been calculated for 16 chromium compounds. A knowledge of these parameters will enable further progress in using ${}^{53}\mathrm{Cr}$ magnetic resonance as a probe of electronic and magnetic structures, thereby contributing to the more systematic development of novel materials.

$5d$ transition-metal oxides host a variety of exotic phases due to the comparable strength of Coulomb repulsion and spin-orbit coupling. Herein, by pursuing density-functional studies on a delta-doped quasi-two-dimensional iridate ${\mathrm{Sr}}_3{\mathrm{Ir}}_2{\mathrm{O}}_7$, where a single SrO layer is replaced by LaO layer, we predict the formation of a spin-orbital entangled two-dimensional electron gas (2DEG) which is sharply confined on two ${\mathrm{IrO}}_2$ layers close to the LaO layer. In this bilayer crystal structure, an existing potential well is further augmented with the inclusion of positively charged LaO layer which results in confining the extra valence electron made available by the ${\mathrm{La}}^{3+}$ ion. The confined electron is bound along crystal $a$ direction and is highly mobile in the $bc$ plane. A tight-binding model Hamiltonian involving the $\mathrm{Ir}\text{−}{\mathrm{t}}_{2g}$ orbitals is formulated to provide further insight into the formation of 2DEG. From the band structure point of view, now the existing half-filled $J_{\mathrm{eff}}=1/2$ states are further electron doped to destroy the antiferromagnetic Mott insulating state of ${\mathrm{IrO}}_2$ layers near to the delta-doped layer. This leads to partially occupied Ir upper-Hubbard subbands which host the spin-orbital entangled 2DEG. The ${\mathrm{IrO}}_2$ layers far away from the interface remain insulating and preserve the collinear G-type magnetic ordering of pristine ${\mathrm{Sr}}_3{\mathrm{Ir}}_2{\mathrm{O}}_7$. The conductivity tensors calculated using semiclassical Boltzmann theory at room temperature reveal that the 2DEG exhibits large electrical conductivity of the order of ${10}^{19}{\mathrm{Sm}}^{-1}{\mathrm{s}}^{-1}$.

Refractory high-entropy alloys (RHEAs) show the potential for high-temperature structural materials, but their brittleness and low ductility at room temperature prohibit the processing and further practical applications, which can be characterized by the generalized stacking fault energy (GSFE). However, the local chemical environment varies significantly across parallel GSF planes, resulting in a substantial fluctuation of GSFE values rather than a unique value, which manifests the local nature of GSFE. We proposed an effective descriptor based on the local concentration ratio near the GSF to quantitatively predict the local GSFE of RHEAs. We find that the role of a given element in determining GSFE strongly depends on its valence-electron number relative to other components and the contribution of its $s$ and $d$ electrons to its cohesive properties. Notably, the descriptor not only unifies the local nature of GSFE from simple alloys to RHEAs but also helps to quickly design RHEAs as the involved parameters are easily accessible.

The utilization of orbital transport provides a versatile and efficient spin manipulation mechanism. As interest in orbital-mediated spin manipulation grows, we face a new issue to identify the underlying physics that determines the efficiency of orbital torque (OT). In this study, we systematically investigate the variation of OT governed by orbital Rashba-Edelstein effect at the Cu/oxide interface, as we change the oxide material. We find that OT varies by a factor of $\sim 2$, depending on the oxide. Our results suggest that the active electronic interatomic interaction (hopping) between Cu and the oxygen atom is critical in determining OT. This also gives us an idea of what type of material factors is critical in forming a chiral orbital Rashba texture at the Cu/oxide interface.

Quasi-one-dimensional (1D) magnetic compounds connect the exact solutions of low-dimensional magnetic geometries, which promise quantum spin liquid behavior and exotic quasiparticles, with real-world materials, in which competing magnetic interactions affect their implementation in quantum information science. Here, the structural determination and quasi-1D magnetic behavior of a previously unreported compound, ${\mathrm{Pb}}_5{\mathrm{Re}}_3{\mathrm{O}}_{15}$, is presented. Like the anisotropic triangular $A_3{\mathrm{ReO}}_5{\mathrm{Cl}}_2$ ($A$ = Ba, Sr, Ca) materials, ${\mathrm{Pb}}_5{\mathrm{Re}}_3{\mathrm{O}}_{15}$ contains $\left[{\mathrm{ReO}}_5\right]$ square pyramids inserted into anion-centered quasi-two-dimensional layers and hosts spin-1/2 moments on the ${\mathrm{Re}}^{6+}$ ions. ${\mathrm{Pb}}_5{\mathrm{Re}}_3{\mathrm{O}}_{15}$, however, has a more ideal quasi-1D geometry than the $A_3{\mathrm{ReO}}_5{\mathrm{Cl}}_2$ materials, with larger interchain distances and interlayer spacing. Quasi-1D magnetic behavior in ${\mathrm{Pb}}_5{\mathrm{Re}}_3{\mathrm{O}}_{15}$ is confirmed by fitting the temperature-dependent magnetic susceptibility with the Bonner-Fisher model for a spin-1/2 antiferromagnetically coupled chain, yielding an intrachain coupling constant of $\left|J\right|/k_{\mathrm{B}}=54.5\mathrm{K}$. ${\mathrm{Pb}}_5{\mathrm{Re}}_3{\mathrm{O}}_{15}$ is highly insulating at room temperature, and heat capacity data below 10 K reveal a linear-$T$ contribution that suggests the presence of low-temperature spinon excitations. With a lack of three-dimensional ordering down to at least 0.6 K, ${\mathrm{Pb}}_5{\mathrm{Re}}_3{\mathrm{O}}_{15}$ is proposed as a model system for studying the quantum magnetism of quasi-1D Heisenberg chains in a real-world $5d^1$ antiferromagnetic material.

In this work, by employing a variable-composition evolutionary algorithm combined with first-principles calculations, we have performed a comprehensive structural search for the magnesium silicide (Mg-Si) system and determined a hyperfine pressure-composition phase diagram. Three new pressure-stabilized structures, namely, $P6/mmm\text{−}{\mathrm{MgSi}}_3, Cmmm$-MgSi, and $Pm\overline{3}m\text{−}{\mathrm{Mg}}_3\mathrm{Si}$, are found. Of particular interest is that $P6/mmm\text{−}{\mathrm{MgSi}}_3$ with silicon kagome-lattice characteristic is a single-gap superconductor with a superconducting transition temperature ($T_{\mathrm{c}}$) about 13.7 K (higher than those of the experimental reported kagome superconductors), which is closely associated with strong electron-phonon coupling mainly determined by silicon kagome lattice. Moreover, $Pm\overline{3}m\text{−}{\mathrm{Mg}}_3\mathrm{Si}$ exhibits a zero-dimensional (0D) electride characteristic with the excess electrons trapped in the Mg-based octahedral cavity. Our findings not only refine the phase diagram of the Mg-Si system, but also expend an in-depth comprehension of the structural diversity and unique electronic states in the alkaline-earth metal silicides under high pressure, which also provide insights into exploring the formation and evolution of the structure of the rocky planets.

We present a general-purpose parametrization of the atomic cluster expansion (ACE) for magnesium. The ACE shows outstanding transferability over a broad range of atomic environments and captures physical properties of bulk as well as defective Mg phases in excellent agreement with reference first-principles calculations. We demonstrate the computational efficiency and the predictive power of ACE by calculating properties of extended defects and by evaluating the $P-T$ phase diagram covering temperatures up to 3000 K and pressures up to 80 GPa. We compare the ACE predictions with those of other interatomic potentials, including the embedded-atom method, an angular-dependent potential, and a recently developed neural network potential. The comparison reveals that ACE is the only model among the tested potentials that is able to predict correctly the phase diagram in close agreement with experimental observations.

We investigate the contribution of mixing enthalpy, configurational entropy, vibrational entropy, and electronic entropy towards the thermodynamic stability of $\beta$-(Zr,Nb) phases, to explain discrepancies in experimental observation of irradiated Zr-Nb alloys. Mixing enthalpy, configurational entropy, and electronic free energy alone are insufficient to explain the relative stability of these phases. This emphasises the need for accurate determination of the vibrational free energy contributions, which we calculated using ab initio molecular dynamics. Including vibrational free energy contributions predicts $\beta$-Zr decomposition in to HCP-Zr and $\beta$-Nb at temperatures below $\sim 880$ K, in line with experimental observations. The relative energy difference between $\beta$-Zr decomposition between 600 and 1200 K is small ($<0.1$ eV/atom) and may explain the wide range of apparently stable $\beta$ phases observed in neutron and proton irradiated Zr-Nb alloys. Other factors that may contribute towards the stability of these phases are also discussed.

We have performed a comprehensive, first-principles high-throughput study of the magnetic properties of halide double perovskites, ${\mathrm{Cs}}_2{\mathrm{BB}}^{\prime }{\mathrm{Cl}}_6$, with magnetic ions occupying one or both B and ${\mathrm{B}}^{\prime }$ sites. Our findings indicate a general tendency for these materials to exhibit antiferromagnetic ordering with low Néel temperatures. At the same time, we reveal a few potential candidates that predicted to be ferromagnetic with relatively high Curie temperatures. Achieving ferromagnetic coupling might be feasible via simultaneously alloying at B and ${\mathrm{B}}^{\prime }$ sites with magnetic 3d and nonmagnetic 5d ions. With this approach, we discover that ${\mathrm{Cs}}_2{\mathrm{HgCrCl}}_6$, ${\mathrm{Cs}}_2{\mathrm{AgNiCl}}_6$, and ${\mathrm{Cs}}_2{\mathrm{AuNiCl}}_6$ have high Curie temperatures relative to their peers, with the latter two exhibiting half metallic behavior. Further, this study illuminates the underpinning mechanism of magnetic exchange interactions in halide double perovskites, enabling a deeper understanding of their magnetic behavior. Our findings, especially the discovery of the compounds with robust half metallic properties and high Curie temperatures, hold promise for potential applications in the field of spintronics.

The binary fluorite oxide ${\mathrm{Hf}}_{0.5}{\mathrm{Zr}}_{0.5}{\mathrm{O}}_2$ tends to grab a significant amount of notice due to the distinct and superior ferroelectricity found in its metastable phase. Stabilizing the metastable ferroelectric phase and delineating the underlying growth mechanism, however, are still challenging. Recent discoveries of metastable ferroelectric ${\mathrm{Hf}}_{0.5}{\mathrm{Zr}}_{0.5}{\mathrm{O}}_2$ epitaxially grown on structurally dissimilar perovskite oxides have triggered intensive investigations on the ferroelectricity in materials that are nonpolar in bulk form. Nonetheless, the growth mechanism for the unique fluorite–perovskite heterostructures has yet to be fully explored. Here, we show that the metastable ferroelectric ${\mathrm{Hf}}_{0.5}{\mathrm{Zr}}_{0.5}{\mathrm{O}}_2$ films can be stabilized even on a 1-unit-cell-thick perovskite ${\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_3$ buffer layer. In collaboration with scanning transmittance electron microscopy (STEM)-based characterizations, we show that monolayer reconstructions driven by the valence-dependent interfacial redox reaction of Mn, along with intralayer electron transfers, play a vital role in the formation of a unique heterointerface between the two structurally dissimilar oxides, providing the template monolayer that facilitates the epitaxial growth of the metastable ${\mathrm{Hf}}_{0.5}{\mathrm{Zr}}_{0.5}{\mathrm{O}}_2$ films. Our findings offer significant insights into the stabilization mechanism of the ferroelectric ${\mathrm{Hf}}_{0.5}{\mathrm{Zr}}_{0.5}{\mathrm{O}}_2$, and this mechanism could be extended for exploring functional metastable phases of various metal oxides.

We report a theoretical design of multiferroic ${\mathrm{Lu}}_{1-x}{\mathrm{Ga}}_x\mathrm{Fe}{\mathrm{O}}_3$ based on density functional theory calculations. While bulk $\mathrm{LuFe}{\mathrm{O}}_3$ stabilizes in a nonpolar $Pnma$ structure, varying the concentration of Ga inside ${\mathrm{Lu}}_{1-x}{\mathrm{Ga}}_x\mathrm{Fe}{\mathrm{O}}_3$ is predicted to result in the following structural transitions: $Pnma$ ($x=0-0.29$)$\to P{6}_{3}cm$ ($x=0.29-0.81$)$\to Pna{2}_1$ ($x=0.81-1$). The hexagonal $P{6}_{3}cm$ phase possesses both a finite polarization and weak ferromagnetic moment, while the $Pna{2}_1$ phase is ferroelectric and antiferromagnetic. Moreover, noncollinear magnetism (associated with spin-orbit coupling) is found to be critical for the stabilization of this $P{6}_{3}cm$ phase. Variation of the electronic properties, such as density of states and band gap, are also reported.

The increase of the dielectric permittivity with an electric field and enhanced energy storage properties make antiferroelectrics very attractive for high-power electronic applications needed in emerging green energy technologies and neuromorphic computing platforms. Their exceptional functional properties are closely related to the electric field-induced antiferroelectric↔ferroelectric phase transition, which can be driven toward a critical end point by manipulation with an external electric field. The critical fluctuation of physical properties at the critical end point in ferroelectrics is a promising approach to improve their functional properties. Here, we demonstrate the existence of two critical end points in antiferroelectric ceramics with a ferroelectric-antiferroelectric-paraelectric phase sequence, using the model system ${\mathrm{Pb}}_{0.99}{\mathrm{Nb}}_{0.02}{\left[{\left({\mathrm{Zr}}_{0.57}{\mathrm{Sn}}_{0.43}\right)}_{0.92}{\mathrm{Ti}}_{0.08}\right]}_{0.98}{\mathrm{O}}_3$. The critical fluctuation of the dielectric permittivity in the proximity of the antiferroelectric-to-paraelectric critical end point is responsible for the strong enhancement of the dielectric tunability (by a factor of $>2$) measured at $\approx 395$ K. The enhancement of the energy storage density at $\approx 370$ K is related to the proximity of the ferroelectric-to-antiferroelectric critical end point. These findings open possibilities for material design and pave the way for the next generation of high-energy storage materials.

Topological superconductors have long been sought for their potential use in quantum computing. The type-II Weyl semimetal ${\mathrm{MoTe}}_2$ is an obvious candidate, exhibiting a superconducting state below 500 mK at ambient pressure, but the question remains whether the pairing is conventional $s^{++}$ or topological $s^{+-}$. The application of external pressure favors the superconducting state in ${\mathrm{MoTe}}_2$ and suppresses the structural transition from $1T^{\prime }$ to $T_d$. The competition between the two structures leads to a mixed phase that strongly enhances the disorder present in the system, remarkably without affecting the superconducting transition temperature, in contrast to the expectation of $s^{+-}$ pairing superconductivity. Our thorough analysis of the electrical and Hall resistivities as a function of pressure yields the most accurate temperature-pressure phase diagram available to date for ${\mathrm{MoTe}}_2$ and a detailed view of the relationship between disorder and superconductivity, supporting a conventional $s^{++}$ pairing symmetry.

Segregation of solutes to grain boundaries (GBs) is an important process having a large impact on mechanical properties of metallic alloys. In this work, we show how accurate density functional theory (DFT) calculations can be combined with machine learning methods to obtain reliable GB segregation energies with significantly lower computational efforts compared to a full ab initio approach. First we compare various descriptor sets with respect to their efficiency in predicting segregation energies for arbitrary GB types. Second, we demonstrate that active learning can be employed to optimize the initial training set obtained by DFT calculations. The methodology is applied to the GB segregation of Re in a WRe alloy, which is a well-studied system of technological relevance.

Kagome compounds have garnered attention in the past few years for their intriguing magnetic properties arising from spin frustration dictated by the geometry of the Kagome sublattice. In this paper, we highlight the success of the unconventional hydride route for the fast and easy synthesis of the Kagome compound $\mathrm{K}{\mathrm{V}}_6{\mathrm{Sb}}_6$. High-temperature in situ powder x-ray diffraction (PXRD) studies proved to be useful in hinting at the existence of $\mathrm{K}{\mathrm{V}}_6{\mathrm{Sb}}_6$, identifying its synthesis conditions, and understanding the reaction mechanism. The crystal structure for $\mathrm{K}{\mathrm{V}}_6{\mathrm{Sb}}_6$ was determined from high-resolution PXRD data. The compound has a layered structure $[R\overline{3}m,a=5.5318$(9)$\mathrm{\AA }, c=34.23$(3)$\mathrm{\AA }, V=907.0$(8)${\mathrm{\AA }}^3, Z=3$ at room temperature] and features a Kagome bilayer of V atoms. $\mathrm{K}{\mathrm{V}}_6{\mathrm{Sb}}_6$ is isostructural to the previously reported $\mathrm{Rb}{\mathrm{V}}_6{\mathrm{Sb}}_6$ and $\mathrm{Cs}{\mathrm{V}}_6{\mathrm{Sb}}_6$ compounds. $\mathrm{K}{\mathrm{V}}_6{\mathrm{Sb}}_6$ is thermally stable in vacuum up to 1173 K, as evident from the high-temperature in situ PXRD and differential scanning calorimetric analysis. Investigation of magnetic properties for $\mathrm{K}{\mathrm{V}}_6{\mathrm{Sb}}_6$ between 2 and 300 K reveals temperature-independent paramagnetism and an absence of superconductivity, like the Rb and Cs analogs. Furthermore, we compare the magnetic properties of $\mathrm{K}{\mathrm{V}}_3{\mathrm{Sb}}_5$, another ternary Kagome compound, synthesized via two different methods: the hydride route and the traditional route from elements. Low-temperature transport property measurements of $\mathrm{K}{\mathrm{V}}_6{\mathrm{Sb}}_6$ indicate metallic behavior and an intrinsically low thermal conductivity of $1.0\mathrm{W}{\mathrm{K}}^{-1}{\mathrm{m}}^{-1}$ at 300 K. The layered structure of $\mathrm{K}{\mathrm{V}}_6{\mathrm{Sb}}_6$ makes it an attractive candidate for deintercalation and doping studies to tune both magnetic and transport properties, laying a foundation for further studies.

The dependence of grain-boundary (GB) character on its ability to act as a vacancy sink was investigated. For this, vacancy formation energies at different $\langle 101\rangle$ symmetric-tilt Al GBs were evaluated using atomistic simulations. This information was then used to study the equilibrium segregation of vacancies to the GBs as a function of temperature, grain size, and initial vacancy supersaturation using a multiple-site segregation model. The results show that even though differences in the ability of the GBs to act as a vacancy sink inversely vary with temperature, vacancy supersaturation, and, to a lesser extent, the grain size, such differences are much more sensitive to the GB character. In agreement with previous studies, both low-angle and random high-angle GBs were observed to act as better vacancy sinks than special GBs (such as the coherent twin boundary). More importantly, it was observed that GBs vicinal to the coherent twin boundary (in particular, those with around ${10}^{\circ }$ offset about the coherent twin misorientation) also act as very good sinks for vacancies. Upon closer inspection, few sites in these GBs were found to have very low vacancy formation energies, which act as deep traps for the vacancies. In fact, these sites were observed to be clustered around the core of GB dislocations in the low-angle and vicinal boundaries, and these were the precise sites wherein vacancies were observed to delocalize.