Thermal conductivity is a key materials parameter that is important in combination with other properties for important applications including electronics, thermal barriers and a variety of energy technologies. There are established trends that are useful in finding materials with desirable thermal conductivity. For example, stable stiff lattices typically yield high thermal conductivity, while materials near instabilities have low thermal conductivity. Rattling is widely applied approach for lowering thermal conductivity and is understood as the incorporation of loosely bound ions in a semiconducting framework. It is manifested in low frequency flat optical phonon branches that cross the acoustic branches. We investigate LaRhTe using global optimization crystal structure determination, anharmonic lattice dynamics, and first principles based characterization of bonding. There are two low energy phases, a hexagonal metallic phase and a cubic semiconducting phase. This cubic phase is predicted to be a low thermal conductivity (1.61 W m-1K-1 at 300 K) semiconductor. We elucidate the origins of its low thermal conductivity finding that strong anharmonic phonon scattering, induced by weak bonding of Rh within the cage-like LaTe network, is important. The Rh atoms contribute to low-frequency phonons, while the La-Te system dominates the high-frequency optical phonon branches. This is unexpected based on the chemical characteristics of Rh chalcogenides and the known thermoelectric behavior of La-Te binary phases. It arises due to the structural constraints in the cubic half-Heusler phase leading to a generalized rattling behavior involving Rh. These results show that the rattling concept is more general than usually assumed and can be operative even without the characteristic rattler induced flat optical branches anticrossing the acoustic branches that are often discussed in the context of low thermal conductivity thermoelectrics.

The contradictory relationship between magnetism and ductility in Fe-Co alloys poses a significant challenge to their development. The variations in magnetism and ductility observed in the equiatomic Fe-Co alloy are attributed to the random BCC to ordered B2 transition. The impacts of the ordering behavior, on structural, magnetic, mechanical and thermodynamic properties of the alloy are investigated by using first-principles calculations. The results demonstrate that a disordered BCC structure transforms into a partially ordered B2 phase of approximately (Fe0.7Co0.3)α(Fe0.3Co0.7)β below 950 K, leading to enhanced magnetic, ductility, and hardness, along with variations in elastic and other properties. We map and analyze the temperature dependence of the elastic parameters as function of temperature for the equiatomic random BCC and ordered B2 structures. This points towards strategies for achieving both desirable magnetic and mechanical properties.

The rational design of high-performance semiconductors-particularly those with tunable bandgaps, high carrier mobility, and stability-remains a fundamental challenge in materials science, as traditional trial-and-error approaches struggle to explore vast chemical spaces efficiently. Guided by insights from band-inverted topological materials, we present an integrated high-throughput calculation and machine learning-based workflow that rapidly uncovers previously uncharted semiconductors. The workflow homes in on the non-parabolic band structures produced by inversion to reveal compounds with high mobility and defect tolerance. Starting from topological materials containing heavy IVA-VIIA elements, we generated thousands of crystal structures via light-element substitution-a strategy designed to engineer new semiconductors beyond conventional compositions. Using high-throughput calculations, we computed key electronic and stability properties, training a classification machine learning model on a 50% subset of the data to predict formation energies for the remaining candidates. The developed workflow enabled us to identify 14 new stable semiconductor candidates with promising potential for photovoltaic and thermoelectric applications. These findings demonstrate that the data-driven approach to light-element substitution in topological materials enables the design of promising semiconductors beyond conventional chemical spaces.

TaOsSi has been identified as a material with both topological surface states and signatures of unconventional superconductivity, while at the same time showing indications of two-gap superconductivity. We report investigation of electronic and superconducting properties of TaOsSi and the related superconductor NbOsSi based on electron-phonon coupling. We find that these materials are not near magnetism, which implies that spin-fluctuation pairing is unlikely to be operative. There is a momentum-dependent electron-phonon coupling on a multisheet Fermi surface leading to a superconducting state with a highly anisotropic gap in the clean limit. The state is fully gapped in accord with experimental results. We do not find a conventional two-gap state but rather a continuous variation of the gap on the Fermi surfaces. Thus, it is possible to explain the occurrence of superconductivity in these compounds within a conventional electron-phonon picture. Both NbOsSi and TaOsSi show a Dirac point very close to the Fermi energy, EF, along the X-S line near the S point. In the case of NbOsSi, this is 16 meV below EF at k = (0.5,0.48,0) and in TaOsSi it is 23 meV below EF at k = (0.5,0.46,0). Thus, these materials are superconductors with strong spin orbit, topological superconductivity, and substantial anisotropy of the superconducting order parameter.

Identifying semiconductors with suitable band gaps and high mobility is important for future high performance electronic devices. We find using first principles calculations with ab initio molecular dynamics that layered tetragonal Bi2Si is a stable semiconductor with a sizable indirect band gap of 1.68 eV and ultra-high electrons mobility exceeding 24100 cm2 V-1 s-1 at 300K. Interestingly, the holes mobility of bilayer Bi2Si is 100 times higher than that of monolayer due to the layer coupling. Furthermore, the band gap of Bi2Si can be modulated both by controlling the number of layers and by tensile strain. The band gap of bilayer Bi2Si can be decreased from 1.10 eV to 0.89 eV while the significant change of band gap isn't observed in the monolayer. The mobility of Bi2Si, which significantly exceeds that of Si, points to the possibility of achieving exceptional performance in field effect devices based on electron transport in Bi2Si, furthermore the layered structure may facilitate deposition synthesis and device fabrication.

The development of efficient, cost-effective, and durable electrocatalysts for the hydrogen evolution reaction (HER) remains a cornerstone for realizing sustainable hydrogen energy. However, highly efficient catalysts with low cost for the HER are still very limited. In this study, we employ spin-polarized density functional theory calculations to investigate the catalytic performance of ruthenium (Ru) single-atom catalysts (SACs) anchored on a biphenylene (BPN) substrate. It is found that the unique two-dimensional architecture and electronic characteristics of BPN offer a promising platform for hosting isolated metal atoms. The Ru atom is found to preferentially anchor at the C4 hollow site, yielding a ΔGH* of -0.093 eV, comparable to H on Pt. Furthermore, two Ru decorated BPN (2Ru-BPN) is energetically stable and used as a double atom catalyst (DAC). The active site in 2Ru-BPN can facilitate multiple hydrogen adsorptions with a Gibbs free energy change of about -0.12 eV, and thus promote the H2 evolution along the Tafel pathway under thermoneutral conditions. Thus, this work provides a theoretical blueprint for designing high-performance Ru-based SACs and reinforces the potential of BPN as a next-generation catalyst support in hydrogen production.

A novel carbon-cage network was reported, denoted as C18, found to be a low energy structure by first principles particle swarm structure search. The compound exhibits high temperature electron-phonon ambient pressure superconductivity with Tc = 79 K for elemental doping and can be raised to Tc = 109 K by appropriate hole doping. Analyses of the phonon spectra, molecular dynamics simulations, and enthalpy differences relative to analogous structures synthesized experimentally all suggest that the hole-doped high-Tc structure is a viable candidate for experimental synthesis.

We studied atomic structure of Mg melts at the interface with ferromagnetic Co using first-principles molecular dynamics simulations. The exchange interaction between Co and Mg is weak with an induced interfacial Mg moment of only approximately 0.02 mu B per Mg atom. Nonetheless, magnetism substantially modifies the structure of the solid-liquid interface, with the solid-liquid interfacial distance increasing by 10 %. Magnetism reduces the ordering of the liquid layers while altering their dynamical properties, which may influence interfacial behaviours relevant to nucleation. Additionally, the magnetism of the Co substrate leads to greater energy differences and reduces electron transfer across the interface. These findings offer valuable insights into the role of magnetism at heterogeneous solid-liquid interfaces, advancing our understanding of the intricate interplay between magnetic and electronic effects during solidification.

The versatile properties of two-dimensional materials indicate that they have enormous potential for applications in thermoelectrics. In this work, we proposed a novel layered pentagonal-structured As2Ge crystal and investigated its stability and electronic structure using density functional theory (DFT) calculations. By combining the results of DFT with Boltzmann transport and phonon transport theory, we studied the electronic conductivity, thermal conductivity and thermoelectric transport properties. It was found that the As2Ge monolayer is a stable layered semiconductor with a wide indirect band gap of 2.43 eV. It exhibits a high electron mobility of up to 7595 cm2 V-1 s-1. The n-type monolayer of As2Ge can achieve a remarkable ZT value as high as 4.36 at 1000 K, and the maximal value of ZT in p-type As2Ge is predicted to reach 3.5 at 1000 K.

The interplay of magnetism and superconductivity is of long-standing interest in condensed matter physics. Layered and 2D superconductors provide a particular opportunity for studying this due to the fact that layer substitutions and adlayers can be used to combine superconducting and magnetic materials. Here we investigate the coupling between fcc Fe and SrTiO3 supported FeSe monolayers. We find that Fe on FeSe monolayers energetically prefers a magnetic fcc structure. The interaction between Fe overlayers and the FeSe monolayer is relatively strong, and in particular it can cause both changes in the FeSe orbital nature near the Fermi level and alterations in the magnetic structure. Notably, we find a change from t2g to eg orbital character near the Fermi level with Fe overlayers, with the eg orbital slightly larger with thick Fe overlayers. We discuss the details of the changes and their origin.

The low thermal conductivity of some semiconducting cubic spinel chalcogenides makes them promising for thermoelectric applications. A key challenge is understanding mechanisms for low thermal conductivity in this class of materials. Here, we theoretically investigated two spinel semiconductors CdBi2Se4 and PbBi2Se4. We find that these show intrinsic ultra-low lattice thermal conductivities (kappa l) of 0.52-1.24 W m-1 K-1 at 300 K. We investigated the origin of such low kappa l by analyzing the nature of the chemical bonding in relation to the crystal structure. The interaction between Pb-6s/Bi-6s and Se-4p orbitals was found to generate antibonding states below the Fermi level in the electronic band structures resulting in softening of the lattice of these compounds. The lattice dynamics of these compounds exhibit strong acoustic-optical coupling and avoided-crossing features. The presence of additional anticrossing in PbBi2Se4 is attributed to strong anharmonic vibrations of the Se atoms as a result of the formation of antibonding states by Pb2+ s2 active lone pairs with Se. Further, bridging Se atoms between tetrahedra and octahedra have asymmetric, anisotropic potential energy surfaces along the x, y, and z directions with strong lattice anharmonicity. The electronic band structure exhibits complex degenerate conduction bands, leading to multiple anisotropic carrier pockets with small transport effective masses. This nontrivial band structure leads to both high Seebeck coefficient and high conductivity. The estimated maximum thermoelectric figure of merit is approximately 1.32 at 500 K in PbBi2Se4. These findings offer valuable insights for the future design and exploration of thermoelectric materials with low lattice thermal conductivity.

The advantages of Cu-based materials make it a potential catalyst for alkaline hydrogen production reactions (HER), but the inertness of pure Cu restricts its application. Thus, it is very meaningful to seek strategies to improve the catalytic activity. In this work, we designed the 15 modified Cu surface models by integrating single atom doping with surface engineering to be used to explore the catalytic activity of Cu surfaces in alkaline HER and the mechanism of effective adsorption and dissociation of water. The results indicated that the combination of surface engineering with single-atom doping can greatly activate the electro-catalysis activity of copper surface. All these 15 catalysts can effectively achieve hydrogen evolution in alkaline conditions, among which the H2O dissociation energy barriers of Cu(210)-Os and Cu(210)-Ru are just 0.47 eV and 0.60 eV, which are much lower than that of pure Pt(111). Thus, it is expected that Cu(210) doped with proper noble metal elements is an ultra-low-cost and ultra1-high-performance catalyst for alkaline HER. Meanwhile, Os and Ru-doped Cu(110) and Cu(211) surfaces also demonstrate remarkable alkaline HER activity compared with the metal catalysts that have been reported hitherto. These offer a novel concept and theoretical guidance to design cheaper and more efficient HER catalysts.

Here we report a structural phase transition and its possible competition with superconductivity in the suboxide La_5Pb_3O. Upon cooling through T_t = 225 K, La_5Pb_3O transforms from a high-temperature I4/mcm to a low-temperature P4/ncc structure in which La - Pb dimerization along the c-axis occurs. This transition is accompanied by anomalies in the temperature dependence of electrical resistivity and specific heat. High-pressure electrical transport measurements reveal that hydrostatic pressure suppresses the structural transition and possibly induces superconductivity with a maximum superconducting temperature of 10 K. Density functional theory calculations show minimal changes in the electronic density of states and no gap opening at E_F across T_t, suggesting that the transition is driven by bonding effects rather than Fermi surface instability. These findings establish La_5Pb_3O as a promising platform for exploring the interplay between weak structural transitions and superconductivity.

Palladium hydride (PdHx) metallenes are efficient electrocatalysts for the oxygen reduction reaction (ORR) due to their high atomic utilization and optimized oxygen binding energies modulated by interstitial hydrogen. However, their practical application is restricted by the highly unstable nature of interstitial hydrogen at working temperatures around 353 K. Here, we report that the use of Mn effectively locks hydrogen atoms within the Pd metallenes lattice, resulting in high alkaline ORR performance across a temperature range of 303-353 K. In contrast, the ORR activity of PdHx metallenes declines sharply with increasing temperature. At 353 K, the mass activity of PdMnHx metallenes at 0.95 V reaches 1.41 A mg-1, which is 14.1 times higher than that of PdHx metallenes. Multiple spectroscopic analyses and theoretical calculations reveal that strong electronic interactions within the immiscible Pd-Mn alloy are critical for locking interstitial hydrogen, thereby enhancing the ORR activity under high temperatures.

The exploration of anode materials is important for the development of K-ion batteries (KIBs) as the promising alternative of Li-ion batteries. The large ionic radius of K ions greatly constrains the selection of anode materials. We propose the pores with appropriate size in structure can promote the storage of K ions. In this work, we studied the potential of layered carbon with pores as the anode of KIBs with TA-BGY as structural model by combining the first-principles calculations and molecular dynamical (MD) simulations. It is found that the doped N with lone electron pair can promote the adsorption of K ions at the edge of pore. The theoretical capacity of K can reach 796 mAh/g and the open circuit voltage is just 0.6 V. In addition, this structure has the low diffusion barrier of 0.48 eV and high structural stability under high K loading. We posit that N-doped layered carbon TA-BGY, featuring pores, holds the potential to serve as an exceptional anode material for KIBs.

The discovery of nickelate superconductivity provided the first example of a non-copper-based material with superconductivity strongly analogous to the cuprates. However, recent findings raise questions and inconsistencies around the electron counts and doping phase diagrams. We show using superconducting La4Ni3O10 that there are unconventional interlayer and interorbital intrinsic doping effects that render the dx2-y2 occupation similar to the cuprates. The results enable a consistent framework for nickelate superconductivity, while maintaining the connection between cuprate and nickelate superconductors.

Thermoelectric materials can realize the direct conversion between heat and electricity, which provides a new strategy for waste heat treatment and power generation. The dimensionless value ZT determines the efficiency of the device. Here, we report a record ZT maximum of about 6.96 at 700 K by performing first-principles calculations on penta-Bi2X (X = Ge, Sn) monolayers. We verified the stability of all systems and calculated the thermoelectric transport properties. The multiband energy degeneracy leads to large Seebeck coefficients, while the small phonon group velocity and strong anharmonic phonon scattering result in ultra-low thermal conductivity. Thus, in both systems, the higher ZT values are found. The high performance of Bi2Ge and Bi2Sn monolayers provide a new guidance for finding layered thermoelectric materials.