The atomic-level coordination environment plays a decisive role in governing thermal transport; however, a unified framework linking coordination character to thermal transport remains lacking in binary AB compounds. Here, based on a dimensionless parameter $b=f_i+r_{\mathrm{A}}/r_{\mathrm{B}}$, combining bond ionicity and the cation–anion radius ratio, we classify 18 prototypical AB compounds into tetrahedral, octahedral, and cubic coordination configurations. Adopting polymorphic CsBr as a platform, we further elucidate the intrinsic effect of coordination environment on thermal transport and reveal that, because of stronger phonon anharmonicity, the cubic phase consistently exhibits lower thermal transport than its octahedral counterpart. Specifically, we ascribe this enhanced anharmonicity in the cubic phase to its dominant quartic anharmonicity, which stiffens phonons and thus expands the scattering phase space with rising temperature, whereas the octahedral phase, where cubic anharmonicity is slightly stronger than quartic anharmonicity, exhibits slight phonon softening and a weaker temperature dependence of the scattering rates. Anomalously, in sharp contrast to the conventional low-frequency peak observed in the cubic phase, the principal spectral peak of the particle-like thermal conductivity in the octahedral phase originates from the highest-frequency transverse acoustic modes, which exhibit a nearly harmonic character. These findings establish a direct link from coordination geometry to thermal transport, paving the way for lattice thermal conductivity modulation through coordination engineering.

Sodium niobate (${\text{NaNbO}}_3$) is a perovskite oxide and a key component of emerging lead-free antiferroelectric capacitors for high-energy-density applications. However, its performance can be hindered by irreversible phase transitions and leakage currents associated with low electrical resistivity. Defect and doping engineering offers a potential way to overcome these problems, but its use requires a detailed understanding of electronic, ionic, and polaron charge-compensation mechanisms, where the role of polarons remains largely unexplored. Here, we investigate the stability of small hole and electron polarons in rhombohedral ${\text{NaNbO}}_3$, which is a structurally well-defined model system that avoids lattice-dynamical instabilities. Trapping energies are calculated using density functional theory corrected by a Hubbard $U$, using the enforced-piecewise-linearity approach including finite-size scaling. For the small hole-polaron centered on O-$2p$ orbital, we find a trapping energy of $-0.65$ eV and an adiabatic migration barrier of 0.32 eV determined by nudged-elastic-band calculations. In contrast, we show that excess electrons do not self-trap on Nb-$4d$ orbitals, reflecting weak electron-phonon coupling in the conduction band manifold. These results identify oxygen as an intrinsic hole trap in ${\text{NaNbO}}_3$ and highlight the importance of including hole polarons in defect models of ${\text{NaNbO}}_3$-based electroceramics.

The local structural response to magnetic ordering in polycrystalline ${\mathrm{Cr}}_{0.3}{\mathrm{Fe}}_{0.7}{\mathrm{VO}}_4$ has been examined using synchrotron x-ray diffraction, x-ray absorption fine structure, and Raman spectroscopy. The combined structural analyses indicate that the average M-O (M = Cr/Fe) and V-O coordination environments remain essentially unchanged across the magnetic transition $T_N\simeq 21\mathrm{K}$, implying that nearest-neighbor bond distortions do not play a role in driving the magnetic ordering. Instead, subtle modifications occur at $T_N$ in the intercluster M-O-V linkages, consistent with tilting and/or rotation of ${\mathrm{MO}}_6$ octahedra and ${\mathrm{VO}}_4$ tetrahedra. EXAFS analysis further identifies a tendency toward preferential occupation of the more distorted ${\mathrm{M}}_1$ sites by ${\mathrm{Cr}}^{3+}$ and the more regular ${\mathrm{M}}_2$ sites by ${\mathrm{Fe}}^{3+}$, which shapes the mixed ${\mathrm{d}}^3$–${\mathrm{d}}^3, {\mathrm{d}}^3$–${\mathrm{d}}^5$, and ${\mathrm{d}}^5$–${\mathrm{d}}^5$ exchange interactions in the ${\mathrm{M}}_4{\mathrm{O}}_{16}$ clusters. We propose that five competing superexchange pathways within each cluster give rise to intrinsic intracluster frustration and short-range ordering, which propagates through M-O-V-O-M linkages to modulate geometric frustration at larger length scales. Raman measurements reveal only weak spin-phonon coupling confined to a narrow temperature region of 15–25 K, tentatively attributed to this frustration. These results suggest a hierarchical frustration scenario in which the local cation distribution shapes the exchange network, whereas the subtle interpolyhedral distortions represent a structural response coupled to the evolving magnetic correlations. These interpretations are inferred from structural and macroscopic magnetic data, and direct validation by neutron diffraction, $\mu \mathrm{SR}$, or density functional theory (DFT) calculations is needed.

Carrier mobility and optical absorption are key performance parameters of oxide semiconductors in transparent and flexible displays. We use a newly developed density-functional perturbation theory with a self-consistent Hubbard correction ($\mathrm{DFPT}+U$) to study phonon-limited electron transport and phonon-assisted optical absorption in strained zinc oxide (ZnO). This parameter-free approach accounts for electron-phonon interactions and on-site correlation effects simultaneously. Electronic structures and phonon dispersions are computed under three distinct uniaxial strain directions. Uniaxial tensile strain up to 4.8% along $\left[\overline{1}10\right]$ is found to increase the room-temperature electron mobility by 19% while leaving visible-range optical absorption essentially unchanged. These results demonstrate that moderate strain can selectively enhance carrier transport without degrading optical transparency, and establish $\mathrm{DFPT}+U$ as an effective framework for predicting strain-dependent transport and optical properties in wide-band-gap oxides with implications for strain-engineered display and optoelectronic applications.

Hafnium oxide ${\mathrm{HfO}}_2$, a high-$\kappa$ dielectric, replaced ${\mathrm{SiO}}_2$ and now is a key dielectric in modern silicon devices. ${\mathrm{HfO}}_2$ contains deep traps. The effect of electron and hole localization on traps in ${\mathrm{HfO}}_2$ is studied for the use as a storage medium in modern charge trap flash memory devices (CTFM). In this study, we demonstrate that electrons and holes localized on traps in ${\mathrm{HfO}}_2$ exhibit Coulomb repulsion. Due to Coulomb repulsion, the surface concentration of traps filled with electrons and holes is an order of magnitude lower than the total trap concentration. This effect significantly changes our understanding of the physics of CTFM programming processes. Analysis of the correlation distribution function of localized electrons indicates Wigner crystallization of electrons and holes localized in ${\mathrm{HfO}}_2$. Due to the disordered arrangement of traps, electrons and holes localized on traps in ${\mathrm{HfO}}_2$ form a Wigner glass. In contrast to the Wigner crystal of free electrons, which is formed at helium temperatures, the Wigner glass of electrons and holes localized in ${\mathrm{HfO}}_2$, due to deep traps $W_{\mathrm{t}}=1.25\mathrm{eV}$, is observed at room temperature.

The development of high-efficiency thermoelectric devices is a central challenge in energy-related research. Clathrate compounds provide an excellent platform for investigating the microscopic mechanisms governing thermoelectric performance owing to their unique crystal structures. In this work, we synthesized a series of ${\mathrm{Eu}}_8{\mathrm{Ga}}_x{\mathrm{Ge}}_{46-x}$ samples (nominal $x$ = 14.5–17.5) using vacuum arc melting followed by spark plasma sintering (SPS). X-ray diffraction (XRD) and magnetic measurements reveal a structural transition from the type-I ($\beta$-phase) to the type-VIII ($\alpha$-phase) structure with increasing Ga content. High-temperature transport measurements conducted between 300 and 773 K show a clear semiconductor-to-metal transition as the Ga content decreases. For the first time, the high-temperature thermoelectric properties of this system are reported. A maximum thermoelectric figure of merit $ZT$ of 0.54 is achieved at 623 K for a nominal Ga content of 16.5. To our knowledge, this $ZT$ value is the highest reported experimentally for this material system to date. Complementary first-principles calculations demonstrate that lower Ga concentrations stabilize the $\beta$ phase, whereas higher Ga concentrations favor the $\alpha$ phase. Moreover, the calculations reveal metallic behavior for the $\beta$-phase compositions with $x$ = 14 and 15, while the $\alpha$-phase composition with $x$ = 16 is semiconducting with a band gap of 0.58 eV, in good agreement with experimental observations. The combined experimental and theoretical results elucidate the evolution of the electronic structure across the structural transition and provide valuable insight into the composition-dependent thermoelectric performance of this system.

A two-step surface crystallization reaction was observed on $\mathrm{A}{\mathrm{u}}_{60}\mathrm{C}{\mathrm{u}}_{15.5}\mathrm{A}{\mathrm{g}}_{7.5}\mathrm{S}{\mathrm{i}}_{17}$ metallic glass under the isothermal annealing below the glass transition temperature ($T_g$). First, at $T_{g-20\mathrm{K}}$, the surface enriched with Cu forms a few nanometers thick distribution of plate-shaped Cu crystals. Then, at $T_{g\text{−}10\mathrm{K}}$, catalyzed by the surface Cu crystal, Si with a small amount of Cu crystallizes into a 100-nm-thick nanostructure deeper into the liquidlike-near-surface region. The fast surface diffusion of glass provides the favorable environment for nanocrystal development where the growth mode and structure can be effectively tuned by the temperature.

diffpy.morph addresses a need to gain scientific insights from one-dimensional (1D) scientific spectra in model-independent ways. A powerful approach for this is to take differences between pairs of spectra and look for meaningful changes that might indicate underlying chemical, structural, or other modifications. The challenge is that the difference curve may contain uninteresting differences such as experimental inconsistencies and benign physical changes such as the effects of thermal expansion. diffpy.morph allows researchers to apply simple transformations, or “morphs,” to one of the datasets to remove the unwanted differences, revealing, when they are present, nontrivial differences. diffpy.morph is an open-source Python package available on the Python Package Index and conda-forge. Here, we describe its functionality and apply it to solve a range of experimental challenges on diffraction and pair distribution function data from x-rays and neutrons, though we note that it may be applied to any 1D function in principle.

Based on first-principles calculations, we investigate the magnetoelectric coupling in the multiferroic van der Waals (vdW) heterostructure ${\mathrm{EuSn}}_2{\mathrm{Sb}}_2/{\mathrm{In}}_2{\mathrm{Te}}_3$. We demonstrate that reversing the ferroelectric polarization of the ${\mathrm{In}}_2{\mathrm{Te}}_3$ monolayer switches the easy magnetization axis (EMA) of the ferromagnetic ${\mathrm{EuSn}}_2{\mathrm{Sb}}_2$ monolayer from in-plane to out-of-plane orientation. Unlike previously studied $3d$-electron multiferroic heterostructures, the present rare-earth-based system exhibits a strong interplay between spin-orbit-coupling (SOC)-induced anisotropy and large dipolar shape anisotropy originating from the sizable Eu magnetic moments. Our calculations reveal that polarization reversal induces substantial interfacial charge transfer and band bending, driving a semiconductor-to-metal transition and significant reconstruction of the low-energy electronic structure near the Fermi level. The resulting band shifts and orbital hybridization strongly modify the SOC-induced magnetic anisotropy associated with Eu $4f$ and Sb $5p$ states, whereas the shape anisotropy remains nearly unchanged. Consequently, the balance between SOC- and dipolar-driven anisotropies is reversed, leading to a switching of the EMA. These findings highlight the crucial role of interfacial electronic reconstruction in rare-earth multiferroic heterostructures and provide a viable route toward nonvolatile electrical control of magnetic anisotropy in vdW spintronic devices.

We investigate the failure of fiber bundles containing two independent sources of heterogeneity: structural disorder generated by random fiber misalignment, and strength disorder arising from random breaking thresholds. The macroscopic constitutive response is derived by averaging over the joint disorder space and is validated against computer simulations. We show that the two disorder sources cooperate in stabilizing failure: finite misalignment can transform a bundle that is perfectly brittle for a prescribed threshold distribution into a quasibrittle system exhibiting stable precursor damage. The physical origin of this effect is the response of the surviving bundle to the force released when a fiber fails. When both disorders are finite, the density of critical global elongations vanishes as a square root at the onset of damage. The resulting scarcity of nearly unstable fibers allows early avalanches to arrest under force control. The brittle-quasibrittle phase boundary shifts systematically toward smaller misalignment with increasing system size and exhibits a square-root finite-size scaling. The results indicate that the finite-area brittle region disappears from the interior of the mixed-disorder plane in the thermodynamic limit, while the single-disorder boundaries remain singular. The avalanche statistics further reveal an effective large-event exponent close to 2.2 near the crossover, distinct from the value $3/2$ observed in the single-disorder limits. Increasing misalignment also separates ultimate strength from failure stability: the peak load varies nonmonotonically, whereas the final catastrophic avalanche is progressively reduced. These results demonstrate that geometrical disorder can promote progressive, damage-tolerant failure even when it does not monotonically increase the strength of the bundle.

This study presents a systematic investigation of ${\mathrm{Mn}}_{1-x}{\mathrm{Pb}}_x{\left({\mathrm{Bi}}_{1-y}{\mathrm{Sb}}_y\right)}_2{\mathrm{Te}}_4$ crystals over a wide range of concentrations ($x$ = 10–60%, $y$ = 5–60%). It was found that the value of the bulk band gap is determined exclusively by the Pb concentration and it closes upon approaching Pb 40–50 %, which is consistent with the topological phase transition predicted for this system. The position of the Dirac point is determined by the Pb/Sb ratio, rather than the absolute Sb content. The magnetic properties depend on the dilution of the Mn sublattice by Pb and are less sensitive to Sb. We show that the simultaneous substitution of Mn and Bi allows independent control of the topological phase and the position of the Fermi level.

A previously unreported triangular lattice (TL) antiferromagnet, $\mathrm{TmZnGa}{\mathrm{O}}_4$, was synthesized as single crystals, and its crystal structure, magnetic susceptibilities, and specific heat were reported. Its crystal structure is isomorphic to that of the transverse-field Ising antiferromagnet $\mathrm{TmMgGa}{\mathrm{O}}_4$, with $\mathrm{T}{\mathrm{m}}^{3+}$ ions located in the TLs, separated by a nonmagnetic bilayer composed mainly of $\mathrm{G}{\mathrm{a}}^{3+}$ and $\mathrm{Z}{\mathrm{n}}^{2+}$ ions. The magnetic susceptibilities indicate the dominating antiferromagnetic interactions. The magnetization curves ($M\text{−}H$) exhibit strong easy-$c$-axis anisotropy, with a clear one-third magnetic plateau emerging, consistent with a field-induced up-up-down $\left(\uparrow \uparrow \downarrow \right)$ spin configuration. Instead of forming a conventional long-range magnetic order, the system exhibits two broad humps at 0.11 K and 2.81 K in zero-field specific heat measurements, revealing dominant strong spin fluctuations and pointing to potential relevance to Berezinskii-Kosterlitz-Thouless physics. The above results reveal its future interest in exploring exotic quantum spin states in $\mathrm{TmZnGa}{\mathrm{O}}_4$.

${\mathrm{Ta}}_4{\mathrm{SiTe}}_4$ is a van der Waals material composed of one-dimensional chains that exhibits an exceptionally large thermoelectric power factor below room temperature. However, since this material has only been available as acicular microcrystals, experimental exploration of the electronic properties underlying its giant thermoelectric performance has remained challenging. In this study, we quantitatively evaluate the electronic anisotropy of ${\mathrm{Ta}}_4{\mathrm{SiTe}}_4$ by combining micro-spot angle-resolved photoemission spectroscopy with transport measurements on focused-ion-beam-processed samples. Angle-resolved photoemission spectroscopy shows anisotropic band dispersions along and perpendicular to the crystallographic $c$ axis. Consistently, transport measurements demonstrate that the resistivity perpendicular to the $c$ axis is approximately five times larger than that along the $c$ axis at 200 K. Hall measurements further provide estimates of the carrier concentration, mobility, and an effective band gap of 0.134 ± 0.034 eV. These results reveal the weakly one-dimensional electronic and transport character of ${\mathrm{Ta}}_4{\mathrm{SiTe}}_4$, providing microscopic insight into the origin of its giant thermoelectric response and highlighting the role of moderate electronic dimensionality in enhancing thermoelectric performance.

The mechanical response of graphene oxide (GO) is controlled by oxidation level and functional group composition, yet a clear atomic level picture remains ambiguous due to limitations of classical reactive force fields. Here, we develop a machine learning interatomic potential by fine-tuning a MACE foundation model on density functional theory data. We employ this potential to systematically investigate GO tensile behavior across oxidation levels of 10% to 40% and hydroxyl-to-epoxy (OH/O) ratios of 0 to 3. Our potential accurately reproduces the expected decrease in Young's modulus and ultimate tensile strength with increasing oxidation, correcting the overestimation and dispersion characteristic of ReaxFF predictions. In the elastic and plastic regimes, oxidation level dominates the mechanical response, while the functional group identity remains secondary. In the fracture regime, however, chemical composition becomes significant, controlling ductile/brittle behavior. In highly oxidized, hydroxyl-rich systems, stress relaxation via dehydration, not captured by reactive force fields, critically influences fracture behavior.