Implications and Optimization of Domain Structures in IV-VI High-Entropy Thermoelectric Materials

High-entropy semiconductors are now an important class of materials widely investigated for thermoelectric applications. Understanding the impact of chemical and structural heterogeneity on transport properties in these compositionally complex systems is essential for thermoelectric design. In this work, we uncover the polar domain structures in the high-entropy PbGeSnSe1.5Te1.5 system and assess their impact on thermoelectric properties. We found that polar domains induced by crystal symmetry breaking give rise to well-structured alternating strain fields. These fields effectively disrupt phonon propagation and suppress the thermal conductivity. We demonstrate that the polar domain structures can be modulated by tuning crystal symmetry through entropy engineering in PbGeSnAgxSbxSe1.5+xTe1.5+x. Incremental increases in the entropy enhance the crystal symmetry of the system, which suppresses domain formation and loses its efficacy in suppressing phonon propagation. As a result, the room-temperature lattice thermal conductivity increases from κL = 0.63 Wm-1 K-1 (x = 0) to 0.79 Wm-1 K-1 (x = 0.10). In the meantime, the increase in crystal symmetry, however, leads to enhanced valley degeneracy and improves the weighted mobility from μw = 29.6 cm2 V-1 s-1 (x = 0) to 35.8 cm2 V-1 s-1 (x = 0.10). As such, optimal thermoelectric performance can be achieved through entropy engineering by balancing weighted mobility and lattice thermal conductivity. This work, for the first time, studies the impact of polar domain structures on thermoelectric properties, and the developed understanding of the intricate interplay between crystal symmetry, polar domains, and transport properties, along with the impact of entropy control, provides valuable insights into designing GeTe-based high-entropy thermoelectrics.

Solution-Obtained (NH4)3In0.95Sb0.05Cl6 with High External Photoluminescence Quantum Yield and Excellent Antiquenching Properties

The efficient broad-band emission from low-dimensional metal halides has garnered significant interest. However, most of these materials exhibit poor stability at the operating temperature of light-emitting diodes. In this study, using the solution method (temperature lower than 90 °C), a new compound (NH4)3In0.95Sb0.05Cl6 was obtained with the structure in the Pnma space group featuring unit-cell parameters of a = 12.3871(4) Å, b = 24.9895(9) Å, and c = 7.7844(3) Å. (NH4)3In0.95Sb0.05Cl6 can be prepared by doping (NH4)2InCl5·H2O when the Sb3+ feeding ratio is in the range of 30-80%. Thermal analysis reveals that (NH4)3In0.95Sb0.05Cl6 is stable up to 320 °C. (NH4)3In0.95Sb0.05Cl6 exhibits broad-band yellow-white emission with extremely high internal and external photoluminescence quantum yields of 93 and 77%, respectively. Interestingly, (NH4)3In0.95Sb0.05Cl6 displays remarkable resistance to thermal quenching, retaining 83% of its initial photoluminescence intensity at 80 °C. A white light-emitting diode is fabricated by combining (NH4)3In0.95Sb0.05Cl6 with a commercial phosphor, and a high color rendering of 92.8 was obtained. This work presents an environmentally friendly, efficient, stable UV-excited broad-band emission material for potential solid-state lighting applications.

Metal Sulfide Ion Exchangers: High Acid Stability of Na2xMg2y-xSn4-yS8 (NMS) and Topotactic Conversion to 2D Solid Acids with Semiconducting Character

Metal sulfide ion exchange materials (MSIEs) are of interest for nuclear waste remediation applications. We report the high stability of two structurally related metal sulfide ion exchange materials, Na2xMg2y-xSn4-yS8 (Mg-NMS) and Na2SnS3 (Na-NMS), in strongly acid media, in addition to the preparation of Na2xNi2y-xSn4-yS8 (Ni-NMS). Their formation progress during synthesis is studied with in-situ methods, with the target phases appearing in <15 min, reaction completion in <12 h, and high yields (75-80%). Upon contact with nitric or hydrochloric acid, these materials topotactically exchange Na+ for H+, proceeding in a stepwise protonation pathway for Na5.33Sn2.67S8. Na-NMS is stable in 2 M HNO3 and Mg-NMS is stable in 4 M HNO3 for up to 4 h, while both NMS materials are stable in 6 M HCl for up to 4 days. However, the treatment of Mg-NMS and Na-NMS with 2-6 M H2SO4 reveals a much slower protonation process since after 4 h of contact both NMS and HMS are present in the solution. The resultant protonated materials, H2xMg2y-xSn4-yS8 and H4x[(HyNay-1)1.33xSn4--1.33x]S8, are themselves solid acids and readily react with and intercalate a variety of organic amines, where the band gap of the resultant adduct is influenced by amine choice and can be tuned within the range of 1.88(5)-2.27(5) eV. The work function energy values for all materials were extracted from photoemission yield spectroscopy in air (PYSA) measurements and range from 5.47 (2) to 5.76 (2) eV, and the relative band alignments of the materials are discussed. DFT calculations suggest that the electronic structure of Na2MgSn3S8 and H2MgSn3S8 makes them indirect gap semiconductors with multi-valley band edges, with carriers confined to the [MgSn3S8]2- layers. Light electron effective masses indicate high electron mobilities.

Kanatzidisite: A Natural Compound with Distinctive van der Waals Heterolayered Architecture

New minerals have long been a source of inspiration for the design and discovery. Many quantum materials, including superconductors, quantum spin liquids, and topological materials, have been unveiled through mineral samples with unusual structure types. In this report, we present kanatzidisite, a new naturally occurring material with formula [BiSbS3]2[Te2] and monoclinic symmetry (space group of P21/m) with lattice parameters a = 4.0021(5) Å, b = 3.9963(5) Å, c = 21.1009(10) Å, and β = 95.392(3)°. The mineral exhibits a unique structure consisting of alternating BiSbS3 double van der Waals layers and distorted [Te] square nets essentially forming an array of parallel zigzag Te chains. Our theoretical calculations suggest that the band structure of kanatzidisite may exhibit topological features characteristic of a Dirac semimetal.

Unraveling the Role of Entropy in Thermoelectrics: Entropy-Stabilized Quintuple Rock Salt PbGeSnCdxTe3+x

Entropy-engineered materials are garnering considerable attention owing to their excellent mechanical and transport properties, such as their high thermoelectric performance. However, understanding the effect of entropy on thermoelectrics remains a challenge. In this study, we used the PbGeSnCd_xTe_3+x family as a model system to systematically investigate the impact of entropy engineering on its crystal structure, microstructure evolution, and transport behavior. We observed that PbGeSnTe₃ crystallizes in a rhombohedral structure at room temperature with complex domain structures and transforms into a high-temperature cubic structure at ∼373 K. By alloying CdTe with PbGeSnTe₃, the increased configurational entropy lowers the phase-transition temperature and stabilizes PbGeSnCd_xTe_3+x in the cubic structure at room temperature, and the domain structures vanish accordingly. The high-entropy effect results in increased atomic disorder and consequently a low lattice thermal conductivity of 0.76 W m^-1 K^-1 in the material owing to enhanced phonon scattering. Notably, the increased crystal symmetry is conducive to band convergence, which results in a high-power factor of 22.4 μW cm^-1 K^-1. As a collective consequence of these factors, a maximum ZT of 1.63 at 875 K and an average ZT of 1.02 in the temperature range of 300-875 K were obtained for PbGeSnCd_0.08Te_3.08. This study highlights that the high-entropy effect can induce a complex microstructure and band structure evolution in materials, which offers a new route for the search for high-performance thermoelectrics in entropy-engineered materials.

Luminescent hybrid halides with various centering metal cations (Zn, Cd and Pb) and diverse structures

Organic-inorganic hybrid metal halides have been extensively studied because of their great potential in optoelectronics. Herein, we report three hybrid metal halides (Bmpip)₂ZnBr₄, (Bmpip)₂CdBr₄, and (Bmpip)₈Pb₁₁Br₃₀ (where Bmpip⁺ is 1-butyl-1-methyl-piperidinium, C₁₀H₂₂N⁺). (Bmpip)₂ZnBr₄ and (Bmpip)₂CdBr₄ crystallize in the P2₁/c space group with zero-dimensional crystal structures with [MBr₄]^2- (M = Zn, Cd) tetrahedra isolated by Bmpip⁺. (Bmpip)₈Pb₁₁Br₃₀ crystallizes in the triclinic space group P1̄ with one-dimensional corrugated chains constructed from face-sharing [PbBr₆]^4- octahedra. All of the compounds exhibit excellent ambient and thermal stability. Under UV excitation, all three compounds exhibit very broad emissions. Temperature-dependent photoluminescence measurements indicate that the broad emissions of (Bmpip)₂ZnBr₄ and (Bmpip)₂CdBr₄ can be attributed to both the organic cations and self-trapped excitons (STEs) and that the emission of (Bmpip)₈Pb₁₁Br₃₀ is assigned to STEs. Density functional theory calculations reveal that the three compounds adopt a direct band gap. This work enriches our understanding of the structure types of hybrid metal halides while revealing their diverse emission mechanisms.

Defect-Engineering-Stabilized AgSbTe2 with High Thermoelectric Performance

Thermoelectric (TE) generators enable the direct and reversible conversion between heat and electricity, providing applications in both refrigeration and power generation. In the last decade, several TE materials with relatively high figures of merit (zT) have been reported in the low- and high-temperature regimes. However, there is an urgent demand for high-performance TE materials working in the mid-temperature range (400-700 K). Herein, p-type AgSbTe₂ materials stabilized with S and Se co-doping are demonstrated to exhibit an outstanding maximum figure of merit (zT_max ) of 2.3 at 673 K and an average figure of merit (zT_ave ) of 1.59 over the wide temperature range of 300-673 K. This exceptional performance arises from an enhanced carrier density resulting from a higher concentration of silver vacancies, a vastly improved Seebeck coefficient enabled by the flattening of the valence band maximum and the inhibited formation of n-type Ag₂ Te, and ahighly improved stability beyond 673 K. The optimized material is used to fabricate a single-leg device with efficiencies up to 13.3% and a unicouple TE device reaching energy conversion efficiencies up to 12.3% at a temperature difference of 370 K. These results highlight an effective strategy to engineer high-performance TE material in the mid-temperature range.

Silver Atom Off-Centering in Diamondoid Solid Solutions Causes Crystallographic Distortion and Suppresses Lattice Thermal Conductivity

The class I-III-VI₂ diamondoid compounds with tetrahedral bonding are important semiconductors widely applied in optoelectronics. Understanding their heat transport properties and developing an effective method to predict the diamondoid solid solutions' thermal conductivity will help assess their impact as thermoelectrics. In this work, we investigated in detail the heat transport properties of CuGa_1-xIn_xTe₂ and Cu_1-xAg_xGaTe₂ and found that in the Ag-alloyed solid solutions, the Ag atom off-centering effect results in crystallographic distortion and extra strong acoustic-optical phonon scattering and an extremely low lattice thermal conductivity. Moreover, we integrate the alloy scattering and the off-centering effect with the crystallographic distortion parameter to develop a modified Klemens model that predicts the thermal conductivity of diamondoid solid solutions. Finally, we demonstrate that Cu_1-xAg_xGaTe₂ solid solutions are promising p-type thermoelectric materials, with a maximum ZT of 1.23 at 850 K for Cu_0.58Ag_0.4GaTe₂.

AInSn2S6 (A = K, Rb, Cs)─Layered Semiconductors Based on the SnS2 Structure

RbInSn₂S₆ and CsInSn₂S₆ are yellow two-dimensional (2D) semiconductors featuring anionic SnS₂-type layers of edge-sharing (In/Sn)S₆ octahedra. These structures are directly derived from the parent structure of SnS₂ by replacement of Sn⁴⁺ atoms with A⁺ and In³⁺ atoms. The compounds crystallize, isotypic to the ion-exchange material KInSn₂S₆. They adopt the triclinic space group R3̅m (no. 166). The compounds have similar indirect optical band gaps of 2.31(5) eV for Rb and 2.47(5) eV Cs. The measured work functions for each material are ∼5.38 eV. The density functional theory-calculated effective mass values exhibit strong anisotropy due to the 2D nature of the crystal structures and in the case of CsInSn₂S₆ for hole carriers along the a, b, and c crystallographic directions are 0.30 m₀, 0.34 m₀, and 2.54 m₀, respectively, while for electrons are 0.06 m₀, 0.07 m₀, and 0.47 m₀, respectively.

Photoluminescent Properties of Two-Dimensional Manganese(II)-Based Perovskites with Different-Length Arylamine Cations

The participation of organic cations plays an important role in tuning broad-spectra emissions. Herein, we synthesized a series of Mn(II)-based two-dimensional (2D) halide perovskites with arylamine cations of different lengths having the general formula (C₆H₅(CH₂)_xNH₃)₂MnCl₄ (x = 1-4), with the x = 4 compound reported here for the first time. With the increase in the -(CH₂)- in organic cations, the distance between adjacent inorganic layers increases, causing the title compounds to exhibit different structural distortions. As the Mn-Cl-Mn angular distortion increases, the experimental optical band gaps of the title compounds increase correspondingly. When the angle distortion between the octahedrons of the compounds is similar, the band gaps may also be affected by the distortion of the octahedron itself (the bond-length distortion of 2 is greater than that of 4). Under UV-light irradiation at 298 K, all of the compounds exhibit two emission peaks centered at 480-505 and 610 nm, corresponding to the organic-cation emission and the ⁴T₁(G) to ⁶A₁(S) radiative transition of Mn²⁺ ions, respectively. Among these title compounds, (PPA)₂MnCl₄ [(PPA)⁺ = C₆H₅(CH₂)₃NH₃⁺] exhibits the strongest photoluminescence (PL). The study of the title compounds contributes to an in-depth understanding of the relationship between the structural distortion and optical properties of 2D Mn(II)-based perovskite materials.

Cubic Stuffed-Diamond Semiconductors LiCu3TiQ4 (Q = S, Se, and Te)

Lithium chalcogenides have been understudied, owing to the difficulty in managing the chemical reactivity of lithium. These materials are of interest as potential ion conductors and thermal neutron detectors. In this study, we describe three new cubic lithium copper chalcotitanates that crystallize in the P4̅3m space group. LiCu₃TiS₄, a = 5.5064(6) Å, and LiCu₃TiSe₄, a = 5.7122(7) Å, represent two members of a new stuffed diamond-type crystal structure, while LiCu₃TiTe₄, a = 5.9830(7) Å crystallized into a similar structure exhibiting lithium and copper mixed occupancy. These structures can be understood as hybrids of the zinc-blende and sulvanite structure types. In situ powder X-ray diffraction was utilized to construct a "panoramic" reaction map for the preparation of LiCu₃TiTe₄, facilitating the design of a rational synthesis and uncovering three new transient phases. LiCu₃TiS₄ and LiCu₃TiSe₄ are thermally stable up to 1000 °C under vacuum, while LiCu₃TiTe₄ partially decomposes when slowly cooled to 400 °C. Density functional theory calculations suggest that these compounds are indirect band gap semiconductors. The measured work functions are 4.77(5), 4.56(5), and 4.69(5) eV, and the measured band gaps are 2.23(5), 1.86(5), and 1.34(5) eV for the S, Se, and Te analogues, respectively.

Probing the Optical Response and Local Dielectric Function of an Unconventional Si@MoS2 Core-Shell Architecture

Heterostructures of optical cavities and quantum emitters have been highlighted for enhanced light-matter interactions. A silicon nanosphere, core, and MoS₂, shell, structure is one such heterostructure referred to as the core@shell architecture. However, the complexity of the synthesis and inherent difficulties to locally probe this architecture have resulted in a lack of information about its localized features limiting its advances. Here, we utilize valence electron energy loss spectroscopy (VEELS) to extract spatially resolved dielectric functions of Si@MoS₂ with nanoscale spatial resolution corroborated with simulations. A hybrid electronic critical point is identified ∼3.8 eV for Si@MoS₂. The dielectric functions at the Si/MoS₂ interface is further probed with a cross-sectioned core-shell to assess the contribution of each component. Various optical parameters can be defined via the dielectric function. Hence, the methodology and evolution of the dielectric function herein reported provide a platform for exploring other complex photonic nanostructures.

Mixed Anion Semiconductor In8S2.82Te6.18(Te2)3

The new heteroanionic compound In₈S_2.82Te_6.18(Te₂)₃ crystallizes in the monoclinic space group C2/c with lattice parameters a = 14.2940(6) Å, b = 14.3092(4) Å, c = 14.1552(6) Å, and β = 90.845(3)°. The three-dimensional (3D) framework of In₈S_2.82Te_6.18(Te₂)₃ is composed of a complex 3D network of corner-connected InQ₄ tetrahedra with three Te₂^2- dumbbell dimers per formula unit. The optical bandgap is 1.12(2) eV and the work function is 5.15(5) eV. First-principles electronic structure calculations using density functional theory (DFT) indicate that this material has potential as a p-type thermoelectric material as it is a narrow bandgap semiconductor, incorporates several heavy elements, and has multiple overlapping bands near the valence band maximum.

Hidden Local Symmetry Breaking in Silver Diamondoid Compounds is Root Cause of Ultralow Thermal Conductivity

Typically, conventional structure transitions occur from a low symmetry state to a higher symmetry state upon warming. In this work, an unexpected local symmetry breaking in the tetragonal diamondoid compound AgGaTe₂ is reported, which, upon warming, evolves continuously from an undistorted ground state to a locally distorted state while retaining average crystallographic symmetry. This is a rare phenomenon previously referred to as emphanisis. This distorted state, caused by the weak sd³ orbital hybridization of tetrahedral Ag atoms, causes their displacement off the tetrahedron center and promotes a global distortion of the crystal structure resulting in strong acoustic-optical phonon scattering and an ultralow lattice thermal conductivity of 0.26 W m^-1 K^-1 at 850 K in AgGaTe₂ . The findings explain the underlying reason for the unexpectedly low thermal conductivities of silver-based compounds compared to copper-based analogs and provide a guideline to suppressing heat transport in diamondoid and other materials.

2D Homologous Series SrFMnBiSn+2 (M = Pb, Ag0.5Bi0.5; n = 0, 1) and Commensurately Modulated Sr2F2Bi2/3S2

We report three new mixed-anion two-dimensional (2D) compounds: SrFPbBiS₃, SrFAg_0.5Bi_1.5S₃, and Sr₂F₂Bi_2/3S₂. Their structures as well as the parent compound SrFBiS₂ were refined using single-crystal X-ray diffraction data, with the sequence of SrFBiS₂, SrFPbBiS₃, and SrFAg_0.5Bi_1.5S₃ defining the new homologous series SrFM_nBiS_n+2 (M = Pb, Ag_0.5Bi_0.5; n = 0, 1). Sr₂F₂Bi_2/3S₂ has a different structure, which is modulated with a q vector of 1/3b* and was refined in superspace group X2/m(0β0)00 as well as in the 1 × 3 × 1 superstructure with space group C2/m (with similar results). Sr₂F₂Bi_2/3S₂ features hexagonal layers of alternating [Sr₂F₂]²⁺ and [Bi_2/3S₂]^2-, and the modulated structure arises from the unique ordering pattern of Sr²⁺ cations. SrFPbBiS₃, SrFAg_0.5Bi_1.5S₃, and Sr₂F₂Bi_2/3S₂ are semiconductors with band gaps of 1.31, 1.21, and 1.85 eV, respectively. The latter compound exhibits room temperature red photoluminescence at ∼700 nm.

Theory-guided experimental design in battery materials research

A reliable energy storage ecosystem is imperative for a renewable energy future, and continued research is needed to develop promising rechargeable battery chemistries. To this end, better theoretical and experimental understanding of electrochemical mechanisms and structure-property relationships will allow us to accelerate the development of safer batteries with higher energy densities and longer lifetimes. This Review discusses the interplay between theory and experiment in battery materials research, enabling us to not only uncover hitherto unknown mechanisms but also rationally design more promising electrode and electrolyte materials. We examine specific case studies of theory-guided experimental design in lithium-ion, lithium-metal, sodium-metal, and all-solid-state batteries. We also offer insights into how this framework can be extended to multivalent batteries. To close the loop, we outline recent efforts in coupling machine learning with high-throughput computations and experiments. Last, recommendations for effective collaboration between theorists and experimentalists are provided.

High Thermoelectric Performance in Chalcopyrite Cu1-xAgxGaTe2-ZnTe: Nontrivial Band Structure and Dynamic Doping Effect

The understanding of thermoelectric properties of ternary I-III-VI₂ type (I = Cu, Ag; III = Ga, In; and VI = Te) chalcopyrites is less well developed. Although their thermal transport properties are relatively well studied, the relationship between the electronic band structure and charge transport properties of chalcopyrites has been rarely discussed. In this study, we reveal the unusual electronic band structure and the dynamic doping effect that could underpin the promising thermoelectric properties of Cu_1-xAg_xGaTe₂ compounds. Density functional theory (DFT) calculations and electronic transport measurements suggest that the Cu_1-xAg_xGaTe₂ compounds possess an unusual non-parabolic band structure, which is important for obtaining a high Seebeck coefficient. Moreover, a mid-gap impurity level was also observed in Cu_1-xAg_xGaTe₂, which leads to a strong temperature-dependent carrier concentration and is able to regulate the carrier density at the optimized value for a wide temperature region and thus is beneficial to obtaining the high power factor and high average ZT of Cu_1-xAg_xGaTe₂ compounds. We also demonstrate a great improvement in the thermoelectric performance of Cu_1-xAg_xGaTe₂ by introducing Cu vacancies and ZnTe alloying. The Cu vacancies are effective in increasing the hole density and the electrical conductivity, while ZnTe alloying reduces the thermal conductivity. As a result, a maximum ZT of 1.43 at 850 K and a record-high average ZT of 0.81 for the Cu_0.68Ag_0.3GaTe₂-0.5%ZnTe compound are achieved.

Valence Disproportionation of GeS in the PbS Matrix Forms Pb5Ge5S12 Inclusions with Conduction Band Alignment Leading to High n-Type Thermoelectric Performance

Converting waste heat into useful electricity using solid-state thermoelectrics has a potential for enormous global energy savings. Lead chalcogenides are among the most prominent thermoelectric materials, whose performance decreases with an increase in chalcogen amounts (e.g., PbTe > PbSe > PbS). Herein, we demonstrate the simultaneous optimization of the electrical and thermal transport properties of PbS-based compounds by alloying with GeS. The addition of GeS triggers a complex cascade of beneficial events as follows: Ge²⁺ substitution in Pb²⁺ and discordant off-center behavior; formation of Pb₅Ge₅S₁₂ as stable second-phase inclusions through valence disproportionation of Ge²⁺ to Ge⁰ and Ge⁴⁺. PbS and Pb₅Ge₅S₁₂ exhibit good conduction band energy alignment that preserves the high electron mobility; the formation of Pb₅Ge₅S₁₂ increases the electron carrier concentration by introducing S vacancies. Sb doping as the electron donor produces a large power factor and low lattice thermal conductivity (κ_lat) of ∼0.61 W m^-1 K^-1. The highest performance was obtained for the 14% GeS-alloyed samples, which exhibited an increased room-temperature electron mobility of ∼121 cm² V^-1 s^-1 for 3 × 10¹⁹ cm^-3 carrier density and a ZT of 1.32 at 923 K. This is ∼55% greater than the corresponding Sb-doped PbS sample and is one of the highest reported for the n-type PbS system. Moreover, the average ZT (ZT_avg) of ∼0.76 from 400 to 923 K is the highest for PbS-based systems.

Thermoelectric Performance of the 2D Bi2Si2Te6 Semiconductor

Bi₂Si₂Te₆, a 2D compound, is a direct band gap semiconductor with an optical band gap of ∼0.25 eV, and is a promising thermoelectric material. Single-phase Bi₂Si₂Te₆ is prepared by a scalable ball-milling and annealing process, and the highly densified polycrystalline samples are prepared by spark plasma sintering. Bi₂Si₂Te₆ shows a p-type semiconductor transport behavior and exhibits an intrinsically low lattice thermal conductivity of ∼0.48 W m^-1 K^-1 (cross-plane) at 573 K. The first-principles density functional theory calculations indicate that such low lattice thermal conductivity is derived from the interactions between acoustic phonons and low-lying optical phonons, local vibrations of Bi, the low Debye temperature, and strong anharmonicity result from the unique 2D crystal structure and metavalent bonding of Bi₂Si₂Te₆. The Bi₂Si₂Te₆ exhibits an optimal figure of merit ZT of ∼0.51 at 623 K, which can be further enhanced by the substitution of Bi with Pb. Pb doping leads to a large increase in power factor S²σ, from ∼3.9 μW cm^-1 K^-2 of Bi₂Si₂Te₆ to ∼8.0 μW cm^-1 K^-2 of Bi_1.98Pb_0.02Si₂Te₆ at 773 K, owing to the increase in carrier concentration. Moreover, Pb doping induces a further reduction in the lattice thermal conductivity to ∼0.38 W m^-1 K^-1 (cross-plane) at 623 K in Bi_1.98Pb_0.02Si₂Te₆, due to strengthened point defect (Pb_Bi') scattering. The simultaneous optimization of the power factor and lattice thermal conductivity achieves a peak ZT of ∼0.90 at 723 K and a high average ZT of ∼0.66 at 400-773 K in Bi_1.98Pb_0.02Si₂Te₆.

Antimony doping to enhance luminescence of tin(iv)-based hybrid metal halides

Exploration of Sn4+-based organic–inorganic metal halides and suggests an efficient lone-pair-containing cation doping route to enhance the luminescent performance.

Elucidating and Mitigating High-Voltage Degradation Cascades in Cobalt-Free LiNiO2 Lithium-Ion Battery Cathodes

LiNiO₂ (LNO) is a promising cathode material for next-generation Li-ion batteries due to its exceptionally high capacity and cobalt-free composition that enables more sustainable and ethical large-scale manufacturing. However, its poor cycle life at high operating voltages over 4.1 V impedes its practical use, thus motivating efforts to elucidate and mitigate LiNiO₂ degradation mechanisms at high states of charge. Here, a multiscale exploration of high-voltage degradation cascades associated with oxygen stacking chemistry in cobalt-free LiNiO₂ , is presented. Lattice oxygen loss is found to play a critical role in the local O3-O1 stacking transition at high states of charge, which subsequently leads to Ni-ion migration and irreversible stacking faults during cycling. This undesirable atomic-scale structural evolution accelerates microscale electrochemical creep, cracking, and even bending of layers, ultimately resulting in macroscopic mechanical degradation of LNO particles. By employing a graphene-based hermetic surface coating, oxygen loss is attenuated in LNO at high states of charge, which suppresses the initiation of the degradation cascade and thus substantially improves the high-voltage capacity retention of LNO. Overall, this study provides mechanistic insight into the high-voltage degradation of LNO, which will inform ongoing efforts to employ cobalt-free cathodes in Li-ion battery technology.

Decreasing Structural Dimensionality of Double Perovskites for Phase Stabilization toward Efficient X-ray Detection

Halide double perovskites have attracted substantial attention for optoelectronic applications owing to their low toxicity and high stability. However, double perovskites have strict requirements in terms of the halide type, thus rendering many of their properties unchangeable, including the band gap, atomic number, and carrier transport. By introducing long-chain organic amines, the chloride site of double perovskites can be completely replaced by bromide. Using this strategy, two dimensions silver-indium-bromide double perovskites (PEA)₄AgInBr₈ and (i-BA)₄AgInBr₈ were successfully synthesized [(PEA)⁺ = C₆H₅(CH₂)₂NH₃⁺, (i-BA)⁺ = CH(CH₃)₂CH₂NH₃⁺]. Density functional theory calculations and spectroscopy characterizations were performed to unveil the semiconducting behaviors and photoluminescence properties of the title compounds. Electrical characterization confirms their good carrier-transport property (μτ product: 2.0 × 10^-3 cm² V^-1) and low dark current. Moreover, the presence of heavy atoms, together with the ultrastable baseline contributes to a high X-ray detection sensitivity (185 μC Gy_air^-1 cm^-2), greater than that of most previous double-perovskite detectors. Our work lays the foundation for broadening the family of potential double perovskites, creating a new path for the realization of long-sought perovskites with low toxicity and high stability that retain good optoelectronic performance.

Structure Tuning, Strong Second Harmonic Generation Response, and High Optical Stability of the Polar Semiconductors Na1-xKxAsQ2

The mixed cation compounds Na_1-xK_xAsSe₂ (x = 0.8, 0.65, 0.5) and Na_0.1K_0.9AsS₂ crystallize in the polar noncentrosymmetric space group Cc. The AAsQ₂ (A = alkali metals, Q = S, Se) family features one-dimensional (1D) ¹/_∞[AQ₂^-] chains comprising corner-sharing pyramidal AQ₃ units in which the packing of these chains is dependent on the alkali metals. The parallel ¹/_∞[AQ₂^-] chains interact via short As···Se contacts, which increase in length when the fraction of K atoms is increased. The increase in the As···Se interchain distance increases the band gap from 1.75 eV in γ-NaAsSe₂ to 2.01 eV in Na_0.35K_0.65AsSe₂, 2.07 eV in Na_0.2K_0.8AsSe₂, and 2.18 eV in Na_0.1K_0.9AsS₂. The Na_1-xK_xAsSe₂ (x = 0.8, 0.65) compounds melt congruently at approximately 316 °C. Wavelength-dependent second harmonic generation (SHG) measurements on powder samples of Na_1-xK_xAsSe₂ (x = 0.8, 0.65, 0.5) and Na_0.1K_0.9AsS₂ suggest that Na_0.2K_0.8AsSe₂ and Na_0.1K_0.9AsS₂ have the highest SHG response and exhibit significantly higher laser-induced damage thresholds (LIDTs). Theoretical SHG calculations on Na_0.5K_0.5AsSe₂ confirm its SHG response with the highest value of d₃₃ = 22.5 pm/V (χ₃₃₃⁽²⁾ = 45.0 pm/V). The effective nonlinearity for a randomly oriented powder is calculated to be d_eff = 18.9 pm/V (χ_eff⁽²⁾ = 37.8 pm/V), which is consistent with the experimentally obtained value of d_eff = 16.5 pm/V (χ_eff⁽²⁾ = 33.0 pm/V). Three-photon absorption is the dominant mechanism for the optical breakdown of the compounds under intense excitation at 1580 nm, with Na_0.2K_0.8AsSe₂ exhibiting the highest stability.

In Situ Mechanistic Studies of Two Divergent Synthesis Routes Forming the Heteroanionic BiOCuSe

Heteroanionic materials are a burgeoning class of compounds that offer new properties via the targeted selection of anions. However, understanding the design principles and achieving successful syntheses of new materials in this class are in their infancy. To obtain mechanistic insight and a panoramic view of the reaction progression from beginning to end of the formation of a heteroanionic material, we selected BiOCuSe, a well-known thermoelectric compound, and utilized in situ synchrotron powder diffraction as a function of temperature and time. BiOCuSe is a layered material, which crystallizes in a common mixed anion structure type: ZrSiAsFe. Two reactions of starting materials (Bi₂O₂Se + Cu₂Se and Bi₂O₃ + Bi + 3Cu + 3Se) were studied to determine the effect of precursors on the reaction pathway. Our in situ investigation shows that the ternary-binary Bi₂O₂Se + Cu₂Se reaction proceeds without intermediates to directly form BiOCuSe, while the binary-elemental Bi₂O₃ + Bi + 3Cu + 3Se reaction generates many intermediates before the final product forms. These intermediates include CuSe, Bi₃Se₄, Bi₂Se₃, and Cu₂Se. While the stoichiometric loading of the precursors necessarily dictates the identity of the first intermediates, kinetics also plays a contributing role in stabilizing unexpected intermediates such as CuSe and Bi₃Se₄. Understanding and establishing a link between the selection of precursors and the reaction pathways improves the potential for rational synthesis of heteroanionic materials and solid-state reactions in general.

Ultralow Thermal Conductivity in Diamondoid Structures and High Thermoelectric Performance in (Cu1-xAgx)(In1-yGay)Te2

Owing to the diversity of composition and excellent transport properties, the ternary I-III-VI₂ type diamond-like chalcopyrite compounds are attractive functional semiconductors, including as thermoelectric materials. In this family, CuInTe₂ and CuGaTe₂ are well investigated and achieve maximum ZT values of ∼1.4 at 950 K and an average ZT of 0.43. However, both compounds have poor electrical conductivity at low temperature, resulting in low ZT below 450 K. In this work, we have greatly improved the thermoelectric performance in the quinary diamondoid compound (Cu_0.8Ag_0.2)(In_0.2Ga_0.8)Te₂ by understanding and controlling the effects of different constituent elements on the thermoelectric transport properties. Our combined theoretical and experimental effort indicates that Ga in the In site of the lattice decreases the carrier effective mass and improves the electrical conductivity and power factor of Cu_0.8Ag_0.2In_1-xGa_xTe₂. Furthermore, Ag in the Cu site strongly suppresses the heat transport via the enhanced acoustic phonon-optical phonon coupling effects, leading to the ultralow thermal conductivity of ∼0.49 W m^-1 K^-1 at 850 K in Cu_0.8Ag_0.2In_0.2Ga_0.8Te₂. Defect formation energy calculations suggest intrinsic Cu vacancies introduce defect levels that are important to the temperature-dependent hole density and electrical conductivity. Therefore, we introduced extra Cu vacancies to optimize the hole carrier density and improve the power factor of Cu_0.8Ag_0.2In_0.2Ga_0.8Te₂. As a result, a maximum ZT of ∼1.5 at 850 K and an average ZT of 0.78 in the temperature range of 400-850 K are obtained, which is among the highest in the diamond-like compound family.

Fluoridation of HfO2

Fluoridation of HfO₂ was carried out with three commonly used solid-state fluoridation agents: PVDF, PTFE, and NH₄HF₂. Clear and reproducible differences are observed in the reaction products of the fluoropolymer reagents and NH₄HF₂ with the latter more readily reacting in air. Strong evidence of distinct, previously unreported hafnium oxyfluoride phases is produced by both reactions, and efforts to isolate them were successful for the air-NH₄HF₂ reaction. Synchrotron XRD, ¹⁹F NMR, and elemental analysis were employed to characterize the phase-pure material which appears to be analogous to known Zr-O-F phases with anion-deficient α-UO₃ structures such as Zr₇O₉F₁₀. Comparison with the hydrolysis of β-HfF₄ under identical conditions depicts that the NH₄HF₂ route produces the oxyfluoride with greater selectivity and at lower temperatures. Thermodynamic calculations were employed to explain this result. Potential reaction pathways for the NH₄HF₂ fluoridation of HfO₂ are discussed.

Pressure-induced ferroelectric-like transition creates a polar metal in defect antiperovskites Hg3Te2X2 (X = Cl, Br)

Ferroelectricity is typically suppressed under hydrostatic compression because the short-range repulsions, which favor the nonpolar phase, increase more rapidly than the long-range interactions, which prefer the ferroelectric phase. Here, based on single-crystal X-ray diffraction and density-functional theory, we provide evidence of a ferroelectric-like transition from phase I2₁3 to R3 induced by pressure in two isostructural defect antiperovskites Hg₃Te₂Cl₂ (15.5 GPa) and Hg₃Te₂Br₂ (17.5 GPa). First-principles calculations show that this transition is attributed to pressure-induced softening of the infrared phonon mode Γ₄, similar to the archetypal ferroelectric material BaTiO₃ at ambient pressure. Additionally, we observe a gradual band-gap closing from ~2.5 eV to metallic-like state of Hg₃Te₂Br₂ with an unexpectedly stable R3 phase even after semiconductor-to-metal transition. This study demonstrates the possibility of emergence of polar metal under pressure in this class of materials and establishes the possibility of pressure-induced ferroelectric-like transition in perovskite-related systems.

Generally, ferroelectricity in ABO₃ perovskites is suppressed by hydrostatic compression, but the evidence for pressure-induced ferroelectricity remains elusive. Here, the authors find a direct ferroelectric-like structural transition induced by pressure in defect antiperovskites.

Enabling deeper learning on big data for materials informatics applications

The application of machine learning (ML) techniques in materials science has attracted significant attention in recent years, due to their impressive ability to efficiently extract data-driven linkages from various input materials representations to their output properties. While the application of traditional ML techniques has become quite ubiquitous, there have been limited applications of more advanced deep learning (DL) techniques, primarily because big materials datasets are relatively rare. Given the demonstrated potential and advantages of DL and the increasing availability of big materials datasets, it is attractive to go for deeper neural networks in a bid to boost model performance, but in reality, it leads to performance degradation due to the vanishing gradient problem. In this paper, we address the question of how to enable deeper learning for cases where big materials data is available. Here, we present a general deep learning framework based on Individual Residual learning (IRNet) composed of very deep neural networks that can work with any vector-based materials representation as input to build accurate property prediction models. We find that the proposed IRNet models can not only successfully alleviate the vanishing gradient problem and enable deeper learning, but also lead to significantly (up to 47%) better model accuracy as compared to plain deep neural networks and traditional ML techniques for a given input materials representation in the presence of big data.

In4Pb5.5Sb5S19: A Stable Quaternary Chalcogenide with Low Thermal Conductivity

Transition-metal-based chalcogenides are a series of intriguing semiconductors with applications spanning various fields because of their rich structure and numerous functionalities. This paper reports the crystal structure and basic physical properties of a new quaternary chalcogenide In₄Pb_5.5Sb₅S₁₉. The crystal structure of In₄Pb_5.5Sb₅S₁₉ was determined by both powder and single-crystal X-ray diffraction techniques. In₄Pb_5.5Sb₅S₁₉ crystallizes in the monoclinic system with I2/m space group, and the structure parameters are a = 26.483 Å, b = 3.899 Å, c = 32.696 Å, and β = 111.86°. The polyhedral double chains of Sb³⁺ and Sb/Pb²⁺ as the main cations are parallel to each other and form a Jamesonite-like mineral structure through the short chain links of the distorted In, Pb, and Sb polyhedron. In₄Pb_5.5Sb₅S₁₉ exhibits a moderate experimental band gap of 1.42 eV, indicating its potential for application in solar cells and photocatalysis. In addition, In₄Pb_5.5Sb₅S₁₉ exhibits good ambient stability, and differential scanning calorimetry tests demonstrate that it is stable up to 892 K in a nitrogen atmosphere. Moreover, In₄Pb_5.5Sb₅S₁₉ exhibits extremely low thermal conductivity (0.438-0.478 W m^-1 K^-1 ranging from 300 to 700 K) compared with binary counterparts such as PbS and In₂S₃. Future chemical manipulation via elemental doping or defect engineering may make the title compound a potential thermoelectric or thermal insulating material.

Strong Valence Band Convergence to Enhance Thermoelectric Performance in PbSe with Two Chemically Independent Controls

We present an effective approach to favorably modify the electronic structure of PbSe using Ag doping coupled with SrSe or BaSe alloying. The Ag 4d states make a contribution to in the top of the heavy hole valence band and raise its energy. The Sr and Ba atoms diminish the contribution of Pb 6s² states and decrease the energy of the light hole valence band. This electronic structure modification increases the density-of-states effective mass, and strongly enhances the thermoelectric performance. Moreover, the Ag-rich nanoscale precipitates, discordant Ag atoms, and Pb/Sr, Pb/Ba point defects in the PbSe matrix work together to reduce the lattice thermal conductivity, resulting a record high average ZT_avg of around 0.86 over 400-923 K.

n-Doping of Quantum Dots by Lithium Ion Intercalation

The optical properties of colloidal quantum dots (QDs) are controllable through introduction of excess electrons or holes into their delocalized bands. Crucial to robust and energy-efficient electronic doping of QDs is suitable charge compensation. Compensation by surface modification and substitutional impurities are however not sufficiently controllable to enable effective doping of QDs. This article describes electrochemical n-type doping of CdSe QDs where injected electrons are compensated by interstitial Li⁺ to form Li_xCdSe, x ≤ 0.3. n-type degenerate doping reversibly decreases absorption into the lowest-energy excitonic state of the QD, activates intraband optical transitions, and shifts the photoluminescence of the QD to higher energy. This work establishes electrochemical interstitial doping as a reversible and highly controllable method for tuning the optical properties of colloidal QDs.

Inverse Design of Ultralow Lattice Thermal Conductivity Materials via Materials Database Screening of Lone Pair Cation Coordination Environment

The presence of lone pair (LP) electrons is strongly associated with the disruption of lattice heat transport, which is a critical component of strategies to achieve efficient thermoelectric energy conversion. By exploiting an empirical relationship between lattice thermal conductivity, κ_L, and the bond angles of pnictogen group LP cation coordination environments, we develop an inverse design strategy based on a materials database screening to identify chalcogenide materials with ultralow κ_L for thermoelectrics. Screening the ∼635 000 real and hypothetical inorganic crystals of the Open Quantum Materials Database based on the constituent elements, nominal electron counting, LP cation coordination environment, and synthesizability, we identify 189 compounds expected to exhibit ultralow κ_L. As a validation, we explicitly compute the lattice dynamical properties of two of the compounds (Cu₂AgBiPbS₄ and MnTl₂As₂S₅) using first-principles calculations and successfully find both achieve ultralow κ_L values at room temperature of ∼0.3-0.4 W/(m·K) corresponding to the amorphous limit. Our data-driven approach provides promising candidates for thermoelectric materials and opens new avenues for the design of phononic properties of materials.

CeTi2O6-A Promising Oxide for Solar Thermochemical Hydrogen Production

A large entropy of reduction is crucial in achieving materials capable of high-efficiency solar thermochemical hydrogen (STCH) production through two-step thermochemical water splitting cycles. We have recently demonstrated that the onsite electronic entropy of reduction attains an extreme value of 4.26 k_B at 1500 K in Ce⁴⁺ → Ce³⁺ redox reactions, which explains the high performance and uniqueness of CeO₂ as an archetypal STCH material. However, ceria requires high temperatures (T > 1500 °C) to achieve a reasonable reduction extent because of its large reduction enthalpy, which is a major obstacle in practical applications. Therefore, new materials with a large entropy of reduction and lower reduction enthalpy are required. Here, we perform a systematic screening to search for Ce⁴⁺-based oxides which possess thermodynamics superior to CeO₂ for STCH production. We first search the Inorganic Crystal Structure Database (ICSD) and literature for Ce⁴⁺-based oxides and subsequently use density functional theory to compute their reduction enthalpies (i.e., oxygen vacancy formation energies). We find that CeTi₂O₆ with the brannerite structure is the most promising candidate for STCH because it possesses three essential characteristics of an STCH material: (i) a smaller reduction enthalpy compared to ceria yet large enough to split water, (ii) a high thermal stability, as reported experimentally, and (iii) a large entropy of reduction associated with Ce⁴⁺ → Ce³⁺ redox. Our proposed design strategy suggests that further exploration of Ce⁴⁺ oxides for STCH production is warranted.

Direct Visualization of Electric-Field-Induced Structural Dynamics in Monolayer Transition Metal Dichalcogenides

Layered transition metal dichalcogenides offer many attractive features for next-generation low-dimensional device geometries. Due to the practical and fabrication challenges related to in situ methods, the atomistic dynamics that give rise to realizable macroscopic device properties are often unclear. In this study, in situ transmission electron microscopy techniques are utilized in order to understand the structural dynamics at play, especially at interfaces and defects, in the prototypical film of monolayer MoS₂ under electrical bias. Through our sample fabrication process, we clearly identify the presence of mass transport in the presence of a lateral electric field. In particular, we observe that the voids present at grain boundaries combine to induce structural deformation. The electric field mediates a net vacancy flux from the grain boundary interior to the exposed surface edge sites that leaves molybdenum clusters in its wake. Following the initial biasing cycles, however, the mass flow is largely diminished and the resultant structure remains stable over repeated biasing. We believe insights from this work can help explain observations of nonuniform heating and preferential oxidation at grain boundary sites in these materials.

Violation of the T -1 Relationship in the Lattice Thermal Conductivity of Mg3Sb2 with Locally Asymmetric Vibrations

Most crystalline materials follow the guidelines of T ^-1 temperature-dependent lattice thermal conductivity (κ _L ) at elevated temperatures. Here, we observe a weak temperature dependence of κ _L in Mg₃Sb₂, T ^-0.48 from theory and T ^-0.57 from measurements, based on a comprehensive study combining ab initio molecular dynamics calculations and experimental measurements on single crystal Mg₃Sb₂. These results can be understood in terms of the so-called "phonon renormalization" effects due to the strong temperature dependence of the interatomic force constants (IFCs). The increasing temperature leads to the frequency upshifting for those low-frequency phonons dominating heat transport, and more importantly, the phonon-phonon interactions are weakened. In-depth analysis reveals that the phenomenon is closely related to the temperature-induced asymmetric movements of Mg atoms within MgSb₄ tetrahedron. With increasing temperature, these Mg atoms tend to locate at the areas with relatively low force in the force profile, leading to reduced effective 3^rd-order IFCs. The locally asymmetrical atomic movements at elevated temperatures can be further treated as an indicator of temperature-induced variations of IFCs and thus relatively strong phonon renormalization. The present work sheds light on the fundamental origins of anomalous temperature dependence of κ _L in thermoelectrics.

Antiferromagnetic Semiconductor BaFMn0.5Te with Unique Mn Ordering and Red Photoluminescence

Semiconductors possessing both magnetic and optoelectronic properties are rare and promise applications in opto-spintronics. Here we report the mixed-anion semiconductor BaFMn_0.5Te with a band gap of 1.76 eV and a work function of 5.08 eV, harboring both antiferromagnetism (AFM) and strong red photoluminescence (PL). The synthesis of BaFMn_0.5Te in quantitative yield was accomplished using the "panoramic synthesis" technique and synchrotron radiation to obtain the full reaction map, from which we determined that the compound forms upon heating at 850 °C via an intermediate unknown phase. The structure refinement required the use of a (3+1)-dimensional superspace group Cmme(α01/2)0ss. The material crystallizes into a ZrCuSiAs-like structure with alternating [BaF]⁺ and [Mn_0.5Te]^- layers and has a commensurately modulated structure with the q-vector of 1/6a* + 1/6b* + 1/2c* at room temperature arising from the unique ordering pattern of Mn²⁺ cations. Long-range AFM order emerges below 90 K, with two-dimensional short-range AFM correlations above the transition temperature. First-principles calculations indicate that BaFMn_0.5Te is an indirect band gap semiconductor with the gap opening between Te 5p and Mn 3d orbitals, and the magnetic interactions between nearest-neighbor Mn²⁺ atoms are antiferromagnetic. Steady-state PL spectra show a broad strong emission centered at ∼700 nm, which we believe originates from the energy manifolds of the modulated Mn²⁺ sublattice and its defects. Time-resolved PL measurements reveal an increase in excited-state lifetimes with longer probe wavelengths, from 93 ns (at 650 nm) to 345 ns (at 800 nm), and a delayed growth (6.5 ± 0.3 ns) in the kinetics at 800 nm with a concomitant decay (4.1 ± 0.1 ns) at 675 nm. Together, these observations suggest that there are multiple emissive states, with higher energy states populating lower energy states by energy transfer.

Origin of Intrinsically Low Thermal Conductivity in Talnakhite Cu17.6Fe17.6S32 Thermoelectric Material: Correlations between Lattice Dynamics and Thermal Transport

Understanding the nature of phonon transport in solids and the underlying mechanism linking lattice dynamics and thermal conductivity is important in many fields, including the development of efficient thermoelectric materials where a low lattice thermal conductivity is required. Herein, we choose the pair of synthetic chalcopyrite CuFeS₂ and talnakhite Cu_17.6Fe_17.6S₃₂ compounds, which possess the same elements and very similar crystal structures but very different phonon transport, as contrasting examples to study the influence of lattice dynamics and chemical bonding on the thermal transport properties. Chemically, talnakhite derives from chalcopyrite by inserting extra Cu and Fe atoms in the chalcopyrite lattice. The CuFeS₂ compound has a lattice thermal conductivity of 2.37 W m^-1 K^-1 at 625 K, while Cu_17.6Fe_17.6S₃₂ features Cu/Fe disorder and possesses an extremely low lattice thermal conductivity of merely 0.6 W m^-1 K^-1 at 625 K, approaching the amorphous limit κ_min. Low-temperature heat capacity measurements and phonon calculations point to a large anharmonicity and low Debye temperature in Cu_17.6Fe_17.6S₃₂, originating from weaker chemical bonds. Moreover, Mössbauer spectroscopy suggests that the state of Fe atoms in Cu_17.6Fe_17.6S₃₂ is partially disordered, which induces the enhanced alloy scattering. All of the above peculiar features, absent in CuFeS₂, contribute to the extremely low lattice thermal conductivity of the Cu_17.6Fe_17.6S₃₂ compound.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Accelerated discovery of metallic glasses through iteration of machine learning and high-throughput experiments

With more than a hundred elements in the periodic table, a large number of potential new materials exist to address the technological and societal challenges we face today; however, without some guidance, searching through this vast combinatorial space is frustratingly slow and expensive, especially for materials strongly influenced by processing. We train a machine learning (ML) model on previously reported observations, parameters from physiochemical theories, and make it synthesis method-dependent to guide high-throughput (HiTp) experiments to find a new system of metallic glasses in the Co-V-Zr ternary. Experimental observations are in good agreement with the predictions of the model, but there are quantitative discrepancies in the precise compositions predicted. We use these discrepancies to retrain the ML model. The refined model has significantly improved accuracy not only for the Co-V-Zr system but also across all other available validation data. We then use the refined model to guide the discovery of metallic glasses in two additional previously unreported ternaries. Although our approach of iterative use of ML and HiTp experiments has guided us to rapid discovery of three new glass-forming systems, it has also provided us with a quantitatively accurate, synthesis method-sensitive predictor for metallic glasses that improves performance with use and thus promises to greatly accelerate discovery of many new metallic glasses. We believe that this discovery paradigm is applicable to a wider range of materials and should prove equally powerful for other materials and properties that are synthesis path-dependent and that current physiochemical theories find challenging to predict.

High-pressure discovery of β-NiBi

Herein, we present the discovery of a new high-pressure phase in the Ni-Bi system, β-NiBi, which crystallizes in the TlI structure type. The powerful technique of in situ high-pressure and high-temperature powder X-ray diffraction enabled observation of the formation of β-NiBi and its reversible reconversion to the ambient pressure phase, α-NiBi.