Diamond is renowned for supreme hardness and supersized electronic bandgap, but knowledge is surprisingly incomplete on its prominent mechanical and electronic benchmarks under large loads. Here, using first-principles calculations, we create global mapping of extremal stress (GMES) and related strain and modulus profiles to bring out fresh perspectives on material behaviors at different scales (small versus large) and varieties (tension, compression or shear) of loads, unveiling patterns and trends of mechanical properties and record-shattering maximal stress. Moreover, we construct global mapping of electronic bandgap (GMEB) profiles to set benchmarks for rational modulation of electronic properties of diamond. This distinct protocol offers a fresh expansive view of key benchmarks beyond the prevailing paradigm, highlighting global emergent behaviors of extreme mechanics and electronics of diamond under ultimate elastic strain engineering.

${\mathrm{CuLa}}_2{\mathrm{Ge}}_2{\mathrm{O}}_8$ forms a distorted triangular lattice of quantum spin-1/2 ${\mathrm{Cu}}^{2+}$ ions. A crystal growth method was developed using the traveling-solvent floating zone technique, resulting in the synthesis of a large single crystal ($4\mathrm{mm}\times 4\mathrm{mm}\times 10$ mm). The crystal was characterized with regard to phase purity and crystallinity using powder x-ray diffraction, energy dispersive x-ray analysis, and Laue diffraction, and found to be of excellent quality. The magnetic properties were characterized using dc-susceptibility, magnetization, and heat capacity measurements, which revealed weak magnetic frustration with long-range magnetic order occurring below $T_N=1.14\left(1\right)$ K. The magnetic structure determined using neutron powder diffraction is a commensurate, noncollinear antiferromagnetic structure, different from the ${120}^{\circ }$ order of an equilateral triangular antiferromagnet. The ordered moments lie in the bc-plane, with components $m_b=0.50\left(3\right) {\mu }_B$ and $m_c=0.73\left(5\right) {\mu }_B$ along the b- and c-axes respectively, giving a total ordered moment of $M_{\mathrm{total}}=0.89\left(6\right){\mu }_B/{\mathrm{Cu}}^{2+}$ at 20 mK.

We investigate the low-temperature spin dynamics of epitaxial lithium aluminum ferrite (LAFO) thin films using broadband ferromagnetic resonance (FMR) spectroscopy from 0.44 to 68 K. The results reveal a crossover from conventional cubic anisotropy-dominated behavior at higher temperatures to pronounced linewidth broadening and higher-order anisotropy contributions at cryogenic temperatures. With the magnetic field oriented along the [100] crystallographic direction, the resonance is well-captured by fourfold in-plane and out-of-plane uniaxial anisotropies. In contrast, measurements with the field along the [110] direction reveal the presence of an unusually large sixth-order cubic anisotropy term that is symmetry-suppressed for [100] but becomes apparent under this field orientation at ultralow temperatures, indicating a substantial modification of the anisotropy landscape. Independent linewidth analysis shows a pronounced peak near 8 K and a subtle monotonic enhancement with decreasing temperatures below 2 K, features consistent with dissipation mediated by a bath of two-level systems (TLS) arising from antisite defects and localized ${\mathrm{Fe}}^{3+}$ moments. Comparison with TLS-based models demonstrates that both exchange-coupled impurities and nearly free paramagnetic centers contribute to the observed damping. Our results establish LAFO as a model ferrite system where disorder-induced TLS limit spin coherence at ultralow temperatures, providing new insights into anisotropy engineering, magnetic relaxation, and the design of ferrimagnetic insulators for coherent magnonics. These findings offer a framework for future optimization of growth conditions.

The question of the size effects in metal film resistivity is revisited through a systematic analysis of its temperature dependence ${\rho }_f\left(T\right)$ (4–300 K) for increasing layer thickness (4.1–216 nm). Ag-based model thermal-control coatings involving symmetric ZnO/Ag/ZnO interfaces are used as test beds for the Mayadas-Shatzkes model [Phys. Rev. B 1, 1382 (1970)]. All contributions to electron scattering, i.e., intragrain, grain boundaries (GBs) and interfaces, are considered while taking into account the actual film microstructure as determined from x-ray scattering. Encapsulated Ag films are studied as-deposited but also after a recrystallization annealing. The electron reflection coefficient $R$ at GBs and the interface scattering parameter $p$ are deduced from ${\rho }_f\left(T\right)$ fits. They are found to vary with film thickness and microstructure. The grain disorientation seems to drive $R$, which remains below $\sim 0.1$ as expected for a perturbation parameter in the M-S model. In parallel to grain coarsening, the observed increase in $R$ upon annealing is assigned to the most disoriented and healing-resilient GBs. The metal interfaces are found strongly scattering for electrons in as-deposited samples ($p\simeq 0$) but become nearly perfect reflectors after annealing ($p\simeq 1$). But no cleat-cut correlation of $p$ with interface roughness can be evidenced. A tentative explanation based on the electronic structure of the interfaces is proposed. Inconsistent results are obtained with the widespread procedure of thickness dependent resistivity fits, which implicitly assumes constant $R$ and $p$ values. Beside an increased role of intragrain contribution for the thicker films having the larger grains, it is shown that no single scattering mechanism dominates the film resistivity as expected from the implicit breakdown of the Matthiessen rule as derived from the M-S equation.

We use a recently developed machine-learned moment tensor potential (MTP) trained on data generated with the density functional theory and tailored to amorphous silicon coupled with the activation-relaxation technique nouveau (ARTn) to identify and classify two-level systems (TLSs). The samples generated using MTP recover experimental results and provide average structural and dissipative properties similar to those obtained with a modified Stillinger-Weber potential, including radial distribution function, defect concentration, and internal friction. Atomistic details, however, are significantly different, including the density and type of TLS. In particular, we find that while the density of the TLS involving a bond-hopping mechanism is similar for the two potentials, more complex TLSs, such as those involving a Wooten-Winer-Weaire bond exchange, are about twice as common. Analysis also shows that TLSs, for MTP-based models, are mostly isolated and oscillate independently from each other.

The layered 122-type diluted ferromagnetic semiconductor $(\mathrm{Ba},\mathrm{K}){(\mathrm{Zn},\mathrm{Mn})}_2{\mathrm{As}}_2$ has attracted much attention both for its high Curie temperature up to $\sim 230$ K and for the independent control of charge-carrier and spin concentrations through doping K and Mn atoms at the Ba and Zn sites, respectively. In order to unveil the nature of the ferromagnetism in $(\mathrm{Ba},\mathrm{K}){(\mathrm{Zn},\mathrm{Mn})}_2{\mathrm{As}}_2$, its magnetization process has been studied by x-ray magnetic circular dichroism (XMCD) at the Mn $L_{2,3}$ edge in a wide range of temperature and magnetic field. The average magnetization of the Mn atoms as a function of magnetic field ($M\text{–}H$ curves) at various temperatures could be successfully explained by a mixture of paramagnetic (PM), superparamagnetic (SPM), and ferromagnetic (FM) components as previously reported for GaMnAs, revealing the complex nature of the ferromagnetism in $(\mathrm{Ba},\mathrm{K}){(\mathrm{Zn},\mathrm{Mn})}_2{\mathrm{As}}_2$. The average magnetization of the SPM clusters of different sizes and the FM regions were found to be small compared to those in GaMnAs, which we attribute to the antiferromagnetic interaction between nearest-neighbor Mn atoms in $(\mathrm{Ba},\mathrm{K}){(\mathrm{Zn},\mathrm{Mn})}_2{\mathrm{As}}_2$ on the basis of recent theoretical predictions.

We present a fine-tuned machine learning interatomic potential (MLIP) for all inorganic halide perovskites $\left(A{A}^{\prime }B{B}^{\prime }{X}_6\right)$, which we use to investigate stability trends across 195 968 charge-balanced compositions. The MLIP accurately predicts the relative stability of cubic and distorted phases, capturing octahedral tilting effects that often favor lower-energy or nonperovskite ground states. For the entire set of examined materials, only 2% of compositions are metastable $(\mathrm{\Delta }{\mathrm{H}}_d< 100 \mathrm{meV}/\text{atom})$ in the high-symmetry cubic phase. To rationalize this result, we analyze 23 730 ${\mathrm{Cs}{\mathrm{A}}^{\prime }\mathrm{B}{\mathrm{B}}^{\prime }\mathrm{X}}_6$ compositions and show that stability in the cubic phase correlates with the size mismatch between $A$ and $A^{\prime }$ cations. Because the MLIP yields DFT-quality optimized structures, single-point DFT can be used efficiently to compute energies and band gaps. Assuming the cubic structure instead of the ground state structure, which typically contains various degrees of octahedral distortions, can lead to changes in the band-gap energy of up to 0.50 eV. The MLIP enables vibrational free-energy calculations via phonon density of states, allowing temperature-dependent phase stability predictions. These reveal several compounds that are predicted to transition from the (distorted) ground state phase (at $T=0\mathrm{K}$) to high-symmetry cubic phases at elevated temperatures. Overall, this work provides a tool and dataset of DFT quality $A{A}^{\prime }B{B}^{\prime }{X}_6$ structures for analyzing key $\mathrm{structure}-\mathrm{property}$ relationships and supports the discovery of new perovskite compositions with more realistic stability and band-gap estimates than considering the cubic phase alone.

Uranyl molybdates are important materials for the pyrochemical reprocessing of spent nuclear fuel. Progress in first-principles atomistic modeling and simulation of these materials is desirable but complicated by the presence of $f$ electrons, the effects of strong electron correlations, and the scarcity of experimental data for the validation of models. In this work, we present a first-principles model of solid-phase uranyl molybdates based on the DFT + U level of theory. Initially, pure ${\mathrm{UO}}_2{\mathrm{MoO}}_4$ is synthesized, characterized, and diffuse reflectance spectroscopy is utilized in order to facilitate the validation of such a first-principles model, which is then applied to various sodium-bearing uranates, molybdates, and uranyl molybdates. Crystal structures and formation enthalpies are considered as well as the electronic properties of ${\mathrm{UO}}_2{\mathrm{MoO}}_4$ and the polymorphism of ${\mathrm{Na}}_2{\mathrm{UMo}}_2{\mathrm{O}}_{10}$. Apart from ${\mathrm{UO}}_2{\mathrm{MoO}}_4$, we present independent experimental results for ${\mathrm{Na}}_2{\mathrm{UMo}}_2{\mathrm{O}}_{10}$ by solving controversies in the numerous structural data attributed to this compound.

Frustrated magnetic materials with competing interactions are a rich source of novel emergent phenomena, as frustration inhibits long-range order and may give rise to a quantum spin liquid (QSL) behavior with strong quantum entanglement, topological order, and often fractionalized excitations. Here, we report an in-depth Raman spectroscopic analysis to probe a single crystal of a rare-earth triangular-lattice antiferromagnet, $\mathrm{YbMgGa}{\mathrm{O}}_4$, along the $ab(/ac)$ crystallographic planes. $\mathrm{YbMgGa}{\mathrm{O}}_4$ has recently attracted significant interest as a promising gapless U(1) QSL candidate with a spinon Fermi surface. We observe an underlying broad continuum of excitations, with a possible origin in disorder arising from $\mathrm{M}{\mathrm{g}}^{2+}/\mathrm{G}{\mathrm{a}}^{3+}$ site mixing and a broad distribution of crystal field excitation (CFE) parameters, rather than a single set of well-defined levels. The development of the Fano asymmetry in the low-frequency phonon mode indicates the coupling with the underlying continuum. These underlying excitations are also reflected in the dynamic spin susceptibility estimated from the Raman response. The apparent renormalization of the phonon self-energy parameters at $\sim 50$ K, which are ascribed to the phonon decaying into itinerant underlying continuum excitation from structural disorder, arises with $\mathrm{M}{\mathrm{g}}^{2+}/\mathrm{G}{\mathrm{a}}^{3+}$ site mixing. Additionally, we analyze the angle-resolved polarization measurements for both $ab(/ac)$ crystallographic planes to decipher the symmetry of the phonons, CFEs, and underlying excitations. The observed variations of the phonon mode behavior as a function of incident photon polarization provide evidence of anisotropic light-matter interactions along with the anisotropy in the spin susceptibility, spin-spin correlation length, and phonon renormalization.

We report a comprehensive study of the ternary compound ThIrSn, characterized by a distorted kagome lattice of Th atoms in polycrystalline form. The compound adopts a noncentrosymmetric ZrNiAl-type crystal structure, with cell parameters $a=b=7.5097\left(4\right)\AA$ and $c=4.1042\left(3\right)\AA$. The resistivity and magnetic susceptibility measurements reveal that ThIrSn exhibits metallic behavior, low magnetoresistance, and paramagnetic characteristics. Hall effect measurements have determined that the carrier type is predominantly electrons, following a single-band model. Furthermore, first-principles calculations indicate that the electronic states near the Fermi level are predominantly contributed by Th and Ir. The band structure exhibits Dirac-like crossings and van Hove singularities at the $M$ and $K$ points, suggesting the potential existence of nontrivial topological characteristics. This work not only establishes ThIrSn as a promising platform for investigating potential topological metals, but also advances the study of ternary intermetallic compounds in distorted kagome lattice systems.

We study from ab initio density functional theory calculations the structural and magnetic properties of the crystal ${\mathrm{KCoF}}_3$. We found that the experimentally reported cubic to tetragonal phase transition is due to an electronic first-order Jahn-Teller effect from the $R$ zone boundary point. We also obtain that the magnetic ground state is the G-type antiferromagnetic order, in agreement with the $R$-point Jahn-Teller distortion and that the magnetic moment of the Co atoms contains a strong orbital contribution ($m_L=0.95 {\mu }_B$ in the cubic phase and 0.55 ${\mu }_B$ in the tetragonal phase). Furthermore, we compute the dynamical magnetic effective charges and show that it is zero by symmetry for the Co and they can reach a value as large as 200 ${10}^{-2}{\mu }_{\text{B}}/\text{Å}$ for the apical F anion. This large magnetic effective charge comes from the spin-orbit coupling (50% of the response is from the orbital moment) contrary to the rare-earth manganites and ferrites with similar order of magnitude but originating from the exchange striction mechanism. The fact that the dynamical magnetic effective charges are nonzero also proves that the tetragonal phase of ${\mathrm{KCoF}}_3$ is antimagnetoelectric with a large magnetic sublattice magnetoelectric response of 210 ps/m per spin channel. We also discuss the generality of these magnetic effective charges.

We investigate the impact of $\mathrm{O}{\mathrm{H}}^{-}$ ions incorporation on the lattice strain and spontaneous polarization of $\mathrm{BaTi}{\mathrm{O}}_3$ nanorods synthesized under different conditions. It was confirmed that the lattice strain depends directly on Ba supersaturation, with higher supersaturation leading to an increase in the lattice strain. However, it was shown that crystal growth and observed lattice distortion are not primarily influenced by external strain; rather, $\mathrm{O}{\mathrm{H}}^{-}$ ions incorporation plays a key role in generating internal chemical strains and driving these processes. By using the less reactive $\mathrm{Ti}{\mathrm{O}}_2$ precursor instead of $\mathrm{TiOC}{\mathrm{l}}_2$ and controlling Ba supersaturation, the slower nucleation rate enables more effective regulation of $\mathrm{O}{\mathrm{H}}^{-}$ ions incorporation and crystal growth. This in turn effects both particle size and lattice distortion, leading to $c/a$ ratio of 1.013–1.014. The incorporation of $\mathrm{O}{\mathrm{H}}^{-}$ ions induces lattice elongation along the $c$ axis, contributing to anisotropic growth, increasing of the rod diameter and their growth-induced bending. However, the possibility of the curvature-induced changes in domain morphology of $\mathrm{BaTi}{\mathrm{O}}_3$ nanorods remains almost unexplored. To study the possibility, we perform analytical calculations and finite element modeling, which provide insights into the curvature-induced changes in the strain-gradient, polarization distribution, and domain morphology in $\mathrm{BaTi}{\mathrm{O}}_3$ nanorods. Theoretical results reveal the appearance of the domain stripes in $\mathrm{BaTi}{\mathrm{O}}_3$ nanorod when the curvature exceeds a critical angle. The physical origin of the domain stripes emergence is the tendency to minimize the elastic energy of the nanorod by the domain splitting. These findings suggest that $\mathrm{BaTi}{\mathrm{O}}_3$ nanorods, with curvature-controllable amount of domain stripes, could serve as flexible race-track memory elements for flexotronics and domain-wall electronics. Overall, this work enhances the understanding of how the shape anisotropy, lattice strains, and strain gradients influence the domain morphology of ferroelectric nanorods, offering a pathway for tuning properties of the nanorods for advanced applications in nanoelectronics.

Elastic constants are central material properties, frequently reported in experimental and theoretical studies. While their computation is straightforward in the absence of thermal fluctuations, finite-temperature methods often suffer from poor signal-to-noise ratios, the presence of strong anharmonic effects, or require second-order derivatives with respect to spatial coordinates. Here, we show how to compute elastic constants in thermally ordered and disordered systems by generalizing a noise-cancellation method originally developed for piezoelectric coupling coefficients. A slight strain is applied to an equilibrated solid. Simulations of both the strained and unstrained (or oppositely strained) reference systems are performed using identical thermostatting schemes. As demonstrated theoretically and with generic one-dimensional models, this allows stress differences to be evaluated and elastic constants to be determined with favorable thermal noise. We then apply this approach across a diverse set of systems, spanning crystalline argon, ordered silicon, as well as amorphous silicon, poly(methyl methacrylate), and cellulose derivatives.

Surface oxides are associated with two-level systems (TLSs) that degrade the performance of niobium-based superconducting quantum computing devices. To address this, we introduce a predictive framework for selecting metal capping layers that inhibit niobium oxide formation. Using DFT-calculated oxygen interstitial and vacancy energies as thermodynamic descriptors, we train a logistic regression model on a limited set of experimental outcomes to successfully predict the likelihood of oxide formation beneath different capping materials. This approach identifies Zr, Hf, and Ta as effective diffusion barriers. Our analysis further reveals that the oxide formation energy per oxygen atom serves as an excellent standalone descriptor for predicting barrier performance. By combining this new descriptor with lattice mismatch as a secondary criterion to promote structurally coherent interfaces, we identify Zr, Ta, and Sc as especially promising candidates. This closed-loop strategy integrates first-principles theory, machine learning, and limited experimental data to enable rational design of next-generation materials.