Deorbitalization of a conventional meta-generalized-gradient exchange-correlation approximation replaces its dependence upon the Kohn-Sham (KS) kinetic energy density with a dependence on the density gradient and Laplacian. In principle, that simplification should provide improved computational performance relative to the original meta-generalized-gradient-approximation form because of the shift from an orbital-dependent generalized KS potential to a true KS local potential. Often that prospective gain is lost because of problematic roughness in the density caused by the density Laplacian and consequent roughness in the exchange-correlation potential from the resulting higher-order spatial derivatives of the density in it. We address the problem by constructing a deorbitalizer based on the “${\mathrm{r}}^2\mathrm{SCAN}$ piecewise polynomial”  (RPP) deorbitalizer from A. D. Kaplan and J. P. Perdew [Phys. Rev. Mater. 6, 083803 (2022)] with comparative smoothness of the potential along with retention of constraint satisfaction as design goals. Applied to the ${\mathrm{r}}^2\mathrm{SCAN}$ exchange-correlation functional presented by J. W. Furness et al. [J. Phys. Chem. Lett. 11, 8208 (2020)], we find substantial timing improvements for solid-state calculations over both ${\mathrm{r}}^2\mathrm{SCAN}$ and its earlier deorbitalization for high-precision calculations of structural properties, while improving upon the accuracy of RPP deorbitalization for both solids and molecules.

Using ab initio methodology, we reveal a strain‐mediated approach to precisely tune the magnetoelectric coupling and spin-driven emergent polarization of ${\mathrm{NiX}}_2$ (X = I, Br) monolayers. In the absence of strain, these systems spontaneously stabilize noncollinear spin states that break the inversion symmetry, inducing a ferroelectric polarization in the plane of the material. We show that biaxial and uniaxial strains broadly modulate the magnetoelectric response in these materials through two distinct mechanisms: ($\text{i}$) direct modification of the magnetoelectric tensor components, and ($\text{ii}$) tuning of the characteristic propagation vectors of a spin texture. This dual mechanism enables rather precise control over the magnitude of the spin‐induced electric polarization of these materials. With respect to the achievable magnitude of the electric polarization, we demonstrate the critical role of third nearest‐neighbor spin‐pair contributions, which can increase under strain to levels that compete with or even exceed the polarization driven by first nearest-neighbor effects. These findings offer important insights into low-dimensional piezomagnetoelectricity and expand the possibilities for designing multifunctional 2D straintronic devices.

Quantum size effect (QSE) on the electronic structures of nanoscale antiferromagnets with a monolayer (ML) thickness is of fundamental importance in antiferromagnetic (AFM) spintronics. Here, we have carried out systematic studies on the size-dependent unoccupied electronic states of ML Mn nanoislands on Ag(111) by employing scanning tunneling microscopy/spectroscopy (STM/STS) together with density-functional theory (DFT). According to bias-dependent height profiles, a lower apparent height has been found on the larger Mn island within a bias voltage range of $\pm 1.0\mathrm{eV}$, suggesting a smaller Mn–Ag interlayer distance. Additionally, a single broad $\text{d}I\text{/d}U$ peak from small Mn islands gradually evolves into two distinct peaks at approximately $1.3\text{eV}$ (peak 1) and $1.5\text{eV}$ (peak 2) as the island size increases. On top of that, peaks 1 and 2 move about $0.37\pm 0.05\mathrm{eV}$ and $0.30\pm 0.03\mathrm{eV}$ toward lower energy positions when the area size of the ML Mn island increases. Given the projected density of states (PDOS) deduced from orbital-dependent electronic band structures of ML Mn/Ag(111), two unoccupied $\mathrm{d}I/\mathrm{d}U$ peaks originate from the contributions of out-of-plane Mn-$3d$ orbitals. Further PDOS comparison analyses reveal that the Mn–Ag interlayer coupling develops a stronger energy shift in unoccupied states than the Mn–Mn atomic bonding, yielding the two-peak feature in $\mathrm{d}I/\mathrm{d}U$ spectra resolved experimentally.

We study the effect of the spatial distribution of active force dipoles on the folding pathways and mechanical stability of rigid-elastic networks using Langevin dynamics simulations. While it has been shown by D. Majumdar, et al. [J. Chem. Phys. 163, 114902 (2025)] that a sharp collapse transition is evident in triangular (elastic) bead-spring networks under the action of contractile (or extensile) force dipoles distributed randomly across the network, here, we show that when the spatial distribution is correlated, e.g., like a patch in the center (“active core” model) or a bandlike distribution along the periphery (“active periphery” model), the network undergoes only a partial decrease in size even at large forces, thereby showing an enhanced mechanical stability just from a spatial rearrangement of the active dipoles. Furthermore, an active periphery network exhibits higher mechanical stability initially, for a range of forces, beyond which the active core network becomes more stable. Active fluctuation induced deformation becomes irreversible beyond a threshold force amplitude, which depends on the type of distribution; for a uniform distribution of active dipoles, the irreversibility threshold almost coincides with the critical collapse point, it decreases for the active core network, and is decreased further for the active periphery network. It is demonstrated that irreversibility arises due to plastic deformations, specifically crease formation, which remains irreversible even after the force is turned off or reversed. The folding pathways depend weakly on the temporal stochasticity of the active links, but are highly sensitive to any defects (missing bonds) in the network. Our findings, therefore, suggest active force localization (or delocalization) as a prime method to dynamically alter the mechanical stability and reversibility of the underlying elastic network.

Epitaxial thin films of the lamellar transition metal dichalcogenide ${\mathrm{NiTe}}_2$ have been grown by molecular beam epitaxy on GaAs(111)B substrates. Using in-plane grazing-incidence x-ray diffraction measurements, we show that two distinct epilayers form during growth: (1) an epitaxial interface contact layer, with a 2D hexagonal lattice structure with in-plane lattice parameter matching the GaAs(111)B surface, and (2) the epitaxial ${\mathrm{NiTe}}_2$ thin film. The in-plane lattice constant of the ${\mathrm{NiTe}}_2$ film is observed to increase while the out-of-plane parameter decreases, both approaching their bulk values, as the film thickness increases. The interfacial contact layer is ascribed to Te atoms substituting for the upper As atoms of the GaAs(111)B (2x2) surface on exposure to Te at the onset of growth, forming a (1x1) Ga–Te hexagonal contact layer with no dangling bonds, which acts as a quasi-van der Waals substrate. We show that a similar contact layer is seen also in the growth of other Te and Se compounds. The presence of this interfacial contact layer, which seems universal for chalcogenide growth on GaAs(111)B, may have significance for understanding the electronic and optical properties of epitaxial layered materials in contact with the substrate.

Two-dimensional (2D) iron trihalides $(\mathrm{Fe}{X}_3, X=\mathrm{F}, \mathrm{Cl}, \mathrm{Br}, \mathrm{I})$ are an emerging family of van der Waals magnets whose fundamental physical properties are not yet fully understood. In this work, we present a systematic first-principles study incorporating hybrid functional (HSE06) calculations and Hubbard U corrections to unravel the spin state, magnetic order, electronic structure, and doping response in monolayer $\mathrm{Fe}{X}_3$. The high-spin $(S=5/2)$ state is unequivocally established as the universal local ground state across the series. A chemical tuned magnetic transition is identified: ${\mathrm{FeF}}_3$ adopts Néel-type antiferromagnetic (AFM) order, while ${\mathrm{FeCl}}_3$, ${\mathrm{FeBr}}_3$, and ${\mathrm{FeI}}_3$ are ferromagnetic (FM) semiconductors with Curie temperatures $\left(T_C\right)$ monotonically increasing from 154 K to 238 K. This trend is driven by the competition between direct AFM exchange and halogen-mediated FM superexchange. Electronically, ${\mathrm{FeCl}}_3$ and ${\mathrm{FeBr}}_3$ are identified as bipolar magnetic semiconductors, exhibiting a perfect linear scaling of the band gap with halogen electronegativity. An effective tight-binding model derived from maximally Wannier functions reveals a progressive increase in crystal-field splitting $\left({\mathrm{\Delta }}_{\mathrm{oct}}\right)$ from 3.36 eV to 4.22 eV, underpinning the evolving orbital hierarchy across iron trihalides. Crucially, electron doping induces a nonmonotonic magnetic evolution, from FM to geometrically frustrated AFM (zigzag/stripy), culminating in a reentrant FM state, driven by the competition between kinetic energy minimization and orbital-selective electron correlations. Finally, bilayer systems exhibit a universally robust interlayer AFM coupling driven by $p_z$ orbital-mediated superexchange across the van der Waals gap. Our work provides a complete microscopic picture of the basic magnetic and electronic properties of the 2D $\mathrm{Fe}{X}_3$, establishing them as a highly versatile material platform for tunable magnetism and spintronics.

Ferroelectric hafnia ($\mathrm{Hf}{\mathrm{O}}_2$) holds promise for next-generation memory and logic applications because of its CMOS compatibility. However, the high coercive field required for polarization switching in $\mathrm{Hf}{\mathrm{O}}_2$ remains a critical challenge for efficient device operations. Using first-principles calculations and phenomenological modeling, we predict that hole-doping can reduce the coercive field from 8 MV/cm in undoped hafnia to 6 MV/cm in hafnia doped with 0.2 holes per formula unit (f.u.). In the absence of doping, the reversal of polarization of the $Pca{2}_1$ phase is preferred through the nonpolar, tetragonal $P{4}_2/nmc$ phase. This switching pathway involves the coupling of three hard distortion modes that render undoped hafnia as an improper ferroelectric. The overall energy barrier through this pathway remains unchanged ($\sim 80$ meV/f.u.) upon hole-doping. However, the introduction of holes hardens the polar ${\mathrm{\Gamma }}_2^{-}$ distortion mode that connects the polar $Pca{2}_1$ phase to the nonpolar, orthorhombic Pbcm phase, and reduces the energy barrier from 180 meV/f.u. in undoped hafnia to 80 meV/f.u. at 0.2 holes/f.u. The activation of the latter switching pathway through the Pbcm phase can lead to a reversal in the polarization direction. Overall, hole-doping makes the switching pathway through the Pbcm phase competitive, and renders hafnia as a proper ferroelectric with a lower coercive field.

Transition-metal dichalcogenides host a variety of charge-density-wave phases that couple lattice, charge, and correlation effects. In $1T\text{−}{\mathrm{TaS}}_2$, the commensurate and nearly commensurate states are well characterized, yet the transition near 350 K into the incommensurate phase has lacked direct momentum-resolved insight. Here, we use temperature-dependent angle-resolved photoemission spectroscopy to track the electronic structure across this transition. We observe a suppression of quasiparticle spectral weight at the Brillouin-zone center, coincident with the transport anomaly, but without clear evidence of a full band-gap opening. The transition appears to involve momentum-dependent redistribution of spectral weight, consistent with a loss of coherence that reshapes the Fermi surface while leaving conduction dispersions largely intact. These results suggest that the nearly commensurate–incommensurate transition may not align with a conventional metal-insulator transition picture, but rather as an electronic reconstruction driven by loss of coherence. Our work provides new microscopic insight into the resistivity anomaly near room temperature and may guide design principles for collective electronic switching in transition-metal dichalcogenides.

Transition-metal dichalcogenides have attracted a great deal of attention in the context of two-dimensional materials because of their electronic properties, derived from their layered crystal structures, as well as their exfoliability. Surprisingly, the combination of high pressure and high temperature has been rarely exploited in the study of these systems, although it is expected to be an efficient way of inducing the formation of novel polymorphs. Here, rhenium and carbon disulfide were observed to react at a pressure of 54 GPa in a laser-heated diamond anvil cell to form a hitherto unknown polymorph of rhenium disulfide, denoted as $mP12\text{−}{\mathrm{ReS}}_2$ in the Pearson notation. Its crystal structure was solved and refined using synchrotron single-crystal x-ray diffraction data, revealing that $mP12\text{−}{\mathrm{ReS}}_2$ adopts the arsenopyrite structure type (space group $P{2}_1/c$). The structure is characterized by an extended three-dimensional framework of corner- and edge-sharing distorted ${\mathrm{ReS}}_6$ octahedra. Raman spectroscopy data further confirm the formation and structure of $mP12\text{−}{\mathrm{ReS}}_2$. Remarkably, upon decompression, $mP12\text{−}{\mathrm{ReS}}_2$ was recovered to ambient conditions and found to be stable in air. Thermodynamic, electronic, and bonding properties of the new phase were also studied computationally within the framework of density functional theory. From these, $mP12\text{−}{\mathrm{ReS}}_2$ is found to be semimetallic at 0 GPa, and to have a lower enthalpy than the previously known ${\mathrm{ReS}}_2$ polymorph from $\sim 0.5\mathrm{GPa}$ onwards. The discovery of this new compound warrants further investigations of its physical properties, and may open new possibilities for applications.

We report experimental and theoretical investigations on the quaternary Heusler alloy CoRuTiGe, synthesized using the arc melting technique. Crystal structure analysis reveals a tetragonal structure at room temperature. Magnetization measurements as a function of temperature and magnetic field indicate a ferromagnetic nature with a saturation magnetization of $\sim 0.681{\mu }_{\mathrm{B}}/\mathrm{f}.\mathrm{u}.$ at 5 K. The temperature dependence of electrical resistivity shows a nearly linear decrease in the high-temperature range, indicating the spin gapless semiconductor (SGS) like behavior of the material. This SGS nature is further supported by the weak temperature-dependent carrier concentration and mobility. Hall effect analysis reveals that the anomalous Hall effect in CoRuTiGe arises from both intrinsic and extrinsic mechanisms. Additionally, a well-defined symmetric negative magnetoresistance is observed at low temperatures. These results offer insights that could aid in designing new spin gapless semiconductors with enhanced Curie temperatures for spintronic applications.

In typical rare-earth lanthanide compounds, the localized $4f$ electrons have a weak effect on the electrical conduction, limiting their influence on the Berry curvature and, hence, the intrinsic anomalous Hall effect. A comprehensive study of the magnetic, thermodynamic, and transport properties of single-crystalline NdGaSi, guided by first‐principles calculations, reveals a ferromagnetic ground state that induces a splitting of quasiflat $4f$ electronic bands and positions them near the Fermi energy. The observation of an extraordinarily large intrinsic anomalous Hall conductivity of $1165{\mathrm{\Omega }}^{-1}{\mathrm{cm}}^{-1}$ implies the direct involvement of localized states in the generation of nontrivial band crossings around the Fermi energy. The angle-resolved photoemission spectroscopy measurements provide direct evidence of nontrivial crossing of the $4f$ bands with dispersive bands. These results are remarkable when compared to ferrimagnetic NdAlSi, which differs only in a nonmagnetic atom (a change in the principal quantum number $n$ of the outer $p$ orbital) with the same number of valence electrons and does not exhibit any measurable anomalous Hall conductivity.

Using first-principles calculations, we study the electronic structure of an unexplored Zintl compound, KCdBi. Our calculations establish KCdBi to be a rare example of a strong $Z_2$ topological semimetal. The compound is found to be cleavable with a small cleavage energy ($\sim 0.2\mathrm{J}/{\mathrm{m}}^2$). The nanostructured KCdBi obtained by cleaving turned out to be a topological insulator, causing a semimetal to insulator transition upon dimensionality reduction. A rich phase diagram emerges upon application of an electric field to nanostructured KCdBi, which consists of topological insulating, $Z_2$ topological metallic, weak and strong Rashba phases. This compound thus offers a platform to study nontrivial properties tunable by electric field and dimensionality. Our findings are expected to stimulate experimental investigation of this interesting compound.

Two-dimensional (2D) magnetic materials have attracted significant attention due to their unique properties and potential applications in spintronics. Using first-principles calculations and group theory analysis, we propose a novel two-dimensional chiral magnetic semiconductor ${\mathrm{FeZrCl}}_6$. The monolayer (ML) ${\mathrm{FeZrCl}}_6$ is dynamically stable and hosts a coplanar noncollinear 120° antiferromagnetic ground state on a triangular lattice, characterized by vector-spin chirality. The group theory analysis reveals that this unique magnetic order activates the anomalous Hall effect (AHE) and magneto-optical Kerr effect (MOKE). During collective in-plane spin rotation, both the AHC and Kerr rotation angle exhibit $2\pi /3$ periodicity dependence on the azimuthal angle $\phi$. Furthermore, out-of-plane spin canting generates a finite scalar-spin chirality, producing an emergent real space Berry phase and thereby inducing a chirality-driven topological Hall effect (THE) and topological magneto-optical Kerr effect (TMOKE) without spin-orbit coupling. These findings not only identify a promising material candidate for antiferromagnetic spintronics but also provide profound insights into the antiferromagnetic anomalous transport phenomena.

Heterostructures that involve contacting magnetic and dielectric layers may possess a voltage-controlled magnetic anisotropy (VCMA) of interfacial origin. In such heterostructures, spin dynamics can be excited by an electric field created in the dielectric layer, which provides an opportunity for the development of energy-efficient spintronic and magnonic devices. Here, we theoretically describe the generation of spin waves by an electric-field-induced modulation of the interfacial magnetic anisotropy in antiferromagnet-dielectric bilayers. Our approach is based on atomistic simulations of VCMA-driven spin reorientations, which are performed for the (001)-oriented FeRh and ${\mathrm{Mn}}_2\mathrm{Au}$ films. It is shown that the sinusoidal variation of VCMA gives rise to the steady precession of spins adjacent to the interface, which induces either evanescent or propagating monochromatic spin waves in the antiferromagnetic film. The amplitude of the generated spin wave strongly depends on the frequency of VCMA oscillations, being maximal at about 33 GHz in the FeRh film and 0.9 THz in the ${\mathrm{Mn}}_2\mathrm{Au}$ one. The analysis of simulation data enables us to determine dispersion relations of the propagating spin waves and their decay lengths. Importantly, antiferromagnetic magnons with high frequencies ∼100 GHz and large decay lengths ∼300 nm can be excited in the FeRh/MgO bilayers. Our findings show that the antiferromagnet-dielectric heterostructures possessing VCMA provide the opportunity for an energy-efficient electrical generation of high-frequency spin waves.

First-order magnetoelastic transitions usually involve mechanisms unique to each family of materials. For ${\left(\mathrm{Mn},\mathrm{Fe}\right)}_2\left(\mathrm{P},\mathrm{Si}\right)$ compounds, it is generally predicted that the unit cell distortion occurring at the ferromagnetic transition leads to a strong electronic reconstruction of the Fe $d$ states accompanied by a notable change in magnetic moment. However, there is no experimental consensus on this mechanism. Here, we use x-ray emission spectroscopy (XES) complemented by first-principles calculations, high-energy resolution fluorescence detected x-ray absorption (HERFD-XAS), and resonant inelastic x-ray scattering (RIXS) experiments, to clarify the nature of the first-order transition in a ${\mathrm{Mn}}_{0.74}{\mathrm{Fe}}_{1.23}{\mathrm{P}}_{0.71}{\mathrm{Si}}_{0.32}$ crystal. HERFD-XAS and RIXS data show a minor evolution of the spectral features in the upper part of the $K$-edge for Mn and Fe, consistent with the calculated $4p$ density of states and fingerprinting the transition. In contrast, no significant evolution of the XES spectra is observed when the transition is crossed. In Fe-rich compositions, the calculations indicate that Fe at the $3g$ site develops a magnetic moment (2.43 ${\mu }_B$) that is smaller than that of Mn at the $3g$ site (2.93 ${\mu }_B$), but larger than that of Fe at the $3f$ site (1.48 ${\mu }_B$). Quantitative XES analysis using the IAD method gives a reasonable agreement with the magnetic moments for different ${\left(\mathrm{Mn},\mathrm{Fe}\right)}_2\left(\mathrm{P},\mathrm{Si}\right)$ compositions. However, the reduction of the Fe moment predicted by theory (approx. $-0.6{\mu }_B$) is not observed around the transition. This study indicates that the Fe moment collapse at the transition may be weaker than the theoretically predicted value or more gradual in temperature, suggesting a secondary role for this moment instability in the giant magnetocaloric effect of ${\left(\mathrm{Mn},\mathrm{Fe}\right)}_2\left(\mathrm{P},\mathrm{Si}\right)$ compounds.