Publikační záznamy NTC

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Flash-pulse thermography evaluation of cold spray 316L steel coatings
(Tanger s.r.o, 2025) Moskovchenko, Alexey; Švantner, Michal; Vostřák, Marek; Dlouhá, Žaneta; Houdková, Šárka
This study investigates the application of infrared (IR) thermography for evaluating thermal-sprayed coatings, focusing on distinguishing coatings subjected to different thermal treatments and varying porosity levels. Experimental thermographic analysis demonstrated the capability of IR thermography to differentiate between coating variants. The Fourier transform method and phase analysis at low frequencies proved remarkably effective. This approach enabled the visualization of areas with differing thicknesses in the thermographic images and facilitated detailed analysis through phase-frequency plots. The results highlight the potential of IR thermography as a powerful, non-destructive tool for characterizing thermal-sprayed coatings, offering insights into their structural and thermal properties. This method holds promise for quality control and optimization in industrial applications involving thermal spray processes
Improvement of morphology and electrical properties of boron-doped diamond films via seeding with HPHT nanodiamonds synthesized from 9-borabicyclononane
(2025) Stehlík, Štěpán; Potocky, Stepan; Aubrechtova Dragounova, Katerina; Bělský, Petr; Medlín, Rostislav; Vincze, Andrej; Ekimov, Evgeny A.; Kromka, Alexander
Boron-doped diamond (BDD) films are becoming increasingly popular as electrode materials due to their broad potential window and stability in harsh conditions and environments. Therefore, optimizing the crystal quality and minimizing defect density to maximize electronic properties (e.g. conductivity) of BDD is of great importance. This study investigates the influence of different hydrogenated nanodiamond (H-ND) seeding layers on the growth and properties of BDD films. Three types of seeding H-NDs were examined: detonation (H-DND) and topdown high-pressure high-temperature NDs (TD_HPHT H-ND), and boron-doped NDs (H-BND) newly synthesized at high-pressure high-temperature from an organic precursor. Purified and oxidized BND (O-BND) samples yielded clear, blue, and stable colloidal dispersions. Subsequent thermal hydrogenation reversed their zeta potential from - 32 mV to +44 mV and promoted the seeding of negatively charged surfaces. All three H-ND types formed dense seeding layers on SiO2 and Si/SiOx substrates, which enabled the growth of BDD films by chemical vapor deposition (CVD). Despite variations in initial surface coverage among the seeding layers (13-25 %), all NDs facilitated the growth of fully closed BDD films approximately 1 mu m thick. Significant differences in film morphology and electrical properties were observed. H-BND nucleation yielded the BDD films with the largest crystals (up to 1000 nm) and lowest sheet resistance (400 Omega/sq). This superior performance is attributed to the uniform particle shape and monocrystalline character of H-BND, as corroborated by FTIR, TEM, and SAXS measurements. These findings highlight the critical role of seeding layer properties in determining consequent diamond film evolution and establish H-BNDs as promising seeding material for the growth of high-quality BDD films suitable for electronic and electrochemical applications.
Transition in morphology and properties in bottom-up HPHT nanodiamonds synthesized from chloroadamantane
(2025) Stehlík, Štěpán; Bělský, Petr; Kovářík, Tomáš; Nemeckova, Zuzana; Henych, Jiri; Ukraintsev, Egor; Vlk, Ales; Ledinsky, Martin; Ekimov, Evgeny
Direct bottom-up high pressure high temperature (BU_HPHT) synthesis of nanodiamonds (NDs) from organic precursors excels in the ability to control the size of the resulting BU_HPHT NDs via the temperature of the synthesis. Here we investigated size-dependent thermal, colloidal, and structural properties of the BU_HPHT NDs and focused on the transition in morphology and properties occurring at around 900 degrees C (approximate to 2 nm). Using transmission electron microscopy, small angle X-ray scattering and atomic force microscopy we show that the sub-900 degrees C samples (<2 nm NDs) do not have nanoparticle character but 2D platelet morphology with sub-nm unit thickness. Correspondingly, sub-900 degrees C samples (<2 nm NDs) have a negative zeta potential and hydrophobic character and should be considered as a form of a molecular diamond. The above-900C (>2 nm NDs) samples have nanocrystalline character, positive zeta potential and are dispersible in water similarly to other types of hydrogenated NDs. By in situ Raman spectroscopy experiments, we show that the transition is also related to the structural instability of the oxidized sub-2 nm BU_HPHT NDs.
Evidence of spin and charge density waves in Chromium electronic bands
(2025) Bisti, Federico; Settembri, Paolo; Minár, Jan; Rogalev, Victor A.; Widmer, Roland; Gröning, Oliver; Shi, Ming; Schmitt, Thorsten; Profeta, Gianni; Strocov, Vladimir N.
The incommensurate spin density wave (SDW) of Chromium represents the classic example of itinerant antiferromagnetism induced by the nesting of the Fermi surface, which is further enriched by the co-presence of a charge density wave (CDW). Here, we explore its electronic band structure using soft-X-ray angle-resolved photoemission spectroscopy (ARPES) for a proper bulk-sensitive investigation. We find that the long-range magnetic order gives rise to a very rich ARPES signal, which can only be interpreted with a proper first-principles description of the SDW and CDW, combined with a band unfolding procedure, reaching a remarkable agreement with experiments. Additional features of the SDW order are obscured by superimposed effects related to the photoemission process, which, unexpectedly, are not predicted by the free-electron model for the final states. We demonstrate that, even for excitation photon energies up to 1 keV, a multiple scattering description of the photoemission final states is required.
Impact of hot isostatic pressing on the microstructure of AISI 316L austenitic steel processed by laser direct energy deposition
(2026) Bricín, David; Jansa, Zdeněk; Janová, Denisa; Špirit, Zbyněk; Beneš, Petr; Kubátová, Dana; Kotous, Jakub
This article deals with the microstructural analysis of austenitic steel AISI 316L processed by the direct energy deposition (L-DED) process and further processed by hot isostatic pressing (HIP). The samples for the experiment were made from atomized powder with an average spherical particle size of 55±30 μm. The powder was processed into blocks with dimensions of 33x33x18 mm, using a deposition layer thickness of 0.6 mm and a Zig-Zag deposition strategy. HIP processing was performed at a temperature of 1150 °C and a pressure of 100 MPa. The analysis of the samples consisted of X-ray phase diffraction analysis and scanning lectron microscopy analysis. X-ray phase analysis revealed that the HIP process causes coarsening of the crystallite structure and a change in the residual stresses acting in the (111) plane, where both tensile and compressive stresses were detected after additive manufacturing process, while only compressive stress was measured after HIP processing. From the point of view of microstructural analysis, recrystallization of the structure was observed, including the formation of a twin structure with an increased fraction of special Σ3 grain boundaries. This was accompanied by the coarsening of oxide inclusions.
Illuminating stability and spectral shifts: A DFT+U study of Eu-doped ZnWO4 for visible-light optoelectronics
(2025) Tayyab, Muhammad; Azam, Sikander; Rafiq, Qaiser; Tirth, Vineet; Algahtani, Ali; Rahman, Amin Ur; Ahmad, Syed Sheraz; Khan, M. Tahir
Tungstate-based oxides have attracted significant attention owing to their excellent structural stability, chemical robustness, and versatile optical properties, making them suitable for next-generation optoelectronic and phosphor applications. Among these, ZnWO4 has emerged as a promising host matrix; however, the role of europium (Eu) substitution in modulating its optoelectronic behavior remains underexplored. In this work, we employ spin-polarized density functional theory (DFT) within the GGA + U framework to investigate the structural, electronic, and optical properties of pristine ZnWO4 and Eu-doped ZnWO4 systems. Phonon dispersion analysis confirms dynamical stability for both pristine and doped structures. Eu doping reduces the bandgap, introduces new localized states near the Fermi level, and significantly alters the density of states, thereby enhancing electronic transitions. The optical response reveals a broadened dielectric function, red-shifted absorption edge, and intensified extinction coefficient, consistent with the presence of Eu 4f states. Additionally, reflectivity and energy-loss spectra indicate improved photon-phonon coupling and optical tunability upon doping. These findings highlight that Eu incorporation not only stabilizes the ZnWO4 lattice but also tailors its optoelectronic features, positioning Eu-doped ZnWO4 as a potential candidate for white-light-emitting diodes (wLEDs) and related optoelectronic technologies.
Chitosan nanoparticles in vaccine delivery systems
(Woodhead Publishing, 2024) Acharya, Biswajeet; Behera, Amulyaratna; Deshmukh, Kalim Abdul Rashid; Sagadevan, Suresh; Moharana, Srikanta
Recent advances in nanostructured boron nitride based flame retardant composites: A comprehensive review
(2026) Jayan, Deepthi K.; Deshmukh, Kalim Abdul Rashid
With formerly unattainable control over material properties at the nanoscale, nanotechnology has emerged as a paradigm shift in materials research. Given the increasing demand for fire-resistant materials in industries, the use of nanomaterials in flame-retardant composites has garnered significant attention among their many other uses. The nanostructured boron nitride (BN) is a potential candidate in this area since it possesses outstanding structural and chemical properties and its two-dimensional (2D) structure endows them with thermal stability, high surface area, and natural flame resistance making them extremely valuable for fire safety improvement in many materials. In recent years, progress in the synthesis, functionalization, and use of nanostructured BN in flame retardant composites cast new light on the fundamental processes that underlie their flame-retardant properties but also triggered the creation of new, high-performance flame-retardant materials. This review provides an integral overview of the most recent advancements in nanostructured BN-based flame-retardant composites, systematically exploring the synthesis routes, properties, characterization methods, and flame retardancy mechanisms. The review explores the underlying principles of the flame-resistant BN-based composites, emphasizing their versatile applications in different industries highlighting their vast potential as next-generation flame retardants. The future trends and challenges associated with the extensive utilization of the nanostructured BN in flame retardant applications are briefed. With a detailed description of the state-of-the-art in nanostructured BN with flame-retardant composites, the current review intends to promote research activities in this emerging area leading to the progress of next-generation sustainable flame-retardant materials with excellent performance.With formerly unattainable control over material properties at the nanoscale, nanotechnology has emerged as a paradigm shift in materials research. Given the increasing demand for fire-resistant materials in industries, the use of nanomaterials in flame-retardant composites has garnered significant attention among their many other uses. The nanostructured boron nitride (BN) is a potential candidate in this area since it possesses outstanding structural and chemical properties and its two-dimensional (2D) structure endows them with thermal stability, high surface area, and natural flame resistance making them extremely valuable for fire safety improvement in many materials. In recent years, progress in the synthesis, functionalization, and use of nanostructured BN in flame retardant composites cast new light on the fundamental processes that underlie their flame-retardant properties but also triggered the creation of new, high-performance flame-retardant materials. This review provides an integral overview of the most recent advancements in nanostructured BN-based flame-retardant composites, systematically exploring the synthesis routes, properties, characterization methods, and flame retardancy mechanisms. The review explores the underlying principles of the flame-resistant BN-based composites, emphasizing their versatile applications in different industries highlighting their vast potential as next-generation flame retardants. The future trends and challenges associated with the extensive utilization of the nanostructured BN in flame retardant applications are briefed. With a detailed description of the state-of-the-art in nanostructured BN with flame-retardant composites, the current review intends to promote research activities in this emerging area leading to the progress of next-generation sustainable flame-retardant materials with excellent performance.
Vanadium-Engineered Co2NiSe4 nanomaterial: coupled thermoelectric, piezoelectric, and electronic optimization via DFT+U for advanced energy applications
(2025) Riaz, Ayesha; Azam, Sikander; Rafiq, Qaiser; Khan, Muhammad Tahir; Rahman, Amin Ur; Ahkam, Qazi Muhammad; Hussain, Rafaqat; Khan, Rajwali
The multifunctional potential of quaternary chalcogenides can be dramatically expanded by targeted pointdefect engineering. In this work, we employ density functional theory (DFT) with on-site Coulomb correction (GGA + U) to explore the structural, electronic, optical, thermoelectric, and piezoelectric properties of pristine and dilute vanadium-doped Co2NiSe4 (<= 10 at.%). Our results reveal that V substitution in monoclinic Co2NiSe4 introduces a resonant V d3 impurity level, which simultaneously (i) narrows the electronic band gap from 0.52 eV to 0.30 eV, (ii) lncrease the total spin moment from 3.2 to 3.6 mu B per formula unit, and (iii) triples the density of states at the Fermi level (Ef). These modifications lead to a significant enhancement in electrical conductivity and phonon-defect scattering, collectively boosting the thermoelectric figure of merit (zT) up to approximate to 1.1 at 900 K for 5 at.% V. Concurrently, the dielectric onset red-shifts into the near-infrared, and the dielectric constant and absorption spectrum broaden, enabling broadband light harvesting and potential NIR optoelectronic applications. The piezoelectric modulus e33 also shows a notable 23 % increase, rising to 2.70 C/m2 at 10 % V doping, indicating strong electromechanical coupling driven by lattice distortion and local symmetry breaking. Simulated X-ray absorption spectra at the Co L2,3 edges further reveal redshifted and broadened absorption peaks upon V doping, confirming enhanced Co-V hybridization and an increased unoccupied 3d-state density, which supports improved conductivity and optical response. These mutually reinforcing electronic, vibrational, and electromechanical enhancements position V-doped Co2NiSe4 as a promising multifunctional material platform for integrated heat-to-power conversion, near-infrared photodetection, and spintronic or spin-filter applications. The study highlights how targeted substitutional doping in chalcogenides can unlock simultaneous improvements across energy, sensing, and actuation domains.
Revealing electronic correlations in YNi2B2C using photoemission spectroscopy
(2025) Pulkkinen, Aki Ismo Olavi; Kremer, Geoffroy; Strocov, Vladimir N.; Weber, Frank; Minár, Jan; Monney, Claude
The low-energy electronic structure of materials is crucial to understanding and modeling their physical properties. Angle-resolved photoemission spectroscopy (ARPES) is the best experimental technique to measure this electronic structure, but its interpretation can be delicate. Here we use a combination of density functional theory (DFT) and one-step model of photoemission to decipher the soft x-ray ARPES spectra of the quaternary borocarbide superconductor YNi2B2C. Our analysis reveals the presence of moderate electronic correlations beyond the semilocal DFT within the generalized gradient approximation. We show that DFT and the full potential Korringa-Kohn-Rostoker method combined with the dynamical mean field theory (DFT+DMFT) with average Coulomb interaction U = 3.0 eV and the exchange energy J = 0.9 eV applied to the Ni d-states are necessary for reproducing the experimentally observed SX-ARPES spectra.
Cleaved surfaces and homoepitaxial growth of InBi(001)
(2025) Rehaag, Thomas J.; Mayoh, Daniel A.; Bárta, Tomáš; Slaney-Parker, Freya; Elhoussieny, Ibrahim; Minár, Jan; Bell, Gavin R.
InBi is a semimetal with topologically non-trivial electronic surface states, which is also chemically and structurally compatible with conventional III-V semiconductors. Single crystal InBi has been grown and its (001) cleave surfaces studied. They do not conform to the single Bi-Bi cleave plane previously assumed in band structure studies of the material but instead expose both In- and Bi-terminated surface regions. Crystals cleaved in ultra-high vacuum have been used as substrates for ultra-low temperature homoepitaxy via periodic supply epitaxy (PSE) with alternate Bi and In fluxes. Homoepitaxial growth of good quality InBi was not achieved under these conditions. The 3D and 2D surface structures produced by PSE were studied by reflection high energy electron diffraction and atomic force microscopy. By studying InBi homoepitaxy for the first time, this work highlights the challenge of growing high quality InBi epilayers beyond the ultra-thin heteroepitaxial layers recently demonstrated [Molecules 2024, 29(12), 2825].
Improved prediction of ultrashort pulse laser ablation efficiency
(2025) Redka, David; Vela, Sergio; Spellauge, Maximilian; Minár, Jan; Morales, Miguel; Molpeceres, Carlos; Huber, Heinz Paul
Achieving maximum efficiency and precision in ultrafast laser ablation is crucial for micromachining applications, where advanced models are pivotal to predict and optimize laser-material interactions. Existing models for predicting laser ablation efficiency assume an equivalence between the threshold fluence determined by ablation depth and diameter. However, experimental measurements have shown this assumption does not hold. In this work, we present a new model for ablation efficiency by introducing a minimum ablation depth (d0) into the ablation depth equation, which accounts for the discrepancy between depth and diameter thresholds. We have designated this framework as the threshold-refined ablation model (TRM). Unlike the Furmanski model, which places the fluence corresponding to maximum ablation efficiency at e2 times the threshold fluence, the TRM predicts this maximum occurs at a lower range (three to five times the threshold fluence), aligning with experimental findings. The new model has been validated against single-pulse experiments for metals, glasses, and dielectrics. For most cases, the TRM demonstrates significantly better agreement with experiments, providing enhanced predictive accuracy for sub-ps and fs pulses.
Spin-orbital mixing in the topological ladder of the two-dimensional metal PtTe2
(2025) Qahosh, M.; Masilamani, M.; Boban, H.; Hou, Xiao; Bihlmayer, G.; Mokrousov, Y.; Karain, W.; Minár, Jan; Reinert, F.; Schusser, Jakub; Schneider, C.M.; Plucinski, L.
We visualize the topological ladder and band inversions in PtTe2 using spin-polarized photoemission spectroscopy augmented by three-dimensional momentum imaging. This approach enables the detection of spin polarization in dispersive bands and provides access to topological properties beyond the reach of conventional methods. Extensive mapping of spin-momentum space reveals distinct topological surface states, including a surface Dirac cone at a binding energy ??∼2.3eV and additional states at ??∼1.6eV, ??∼1.0eV, and near the Fermi level. The electronic structure analysis demonstrates strong hybridization between Pt and Te atomic orbitals, confirming the nontrivial topology of these surface states. Furthermore, by comparison to one-step model photoemission calculations, we identify a robust correlation between the initial-state and measured spin polarizations while revealing asymmetries in specific experimental spin textures. These asymmetries, absent in the initial states due to symmetry constraints, arise from the breaking of time-reversal symmetry during the photoemission process, emphasizing the crucial influence of symmetries on experimental signatures of topology. A phase analysis of ladder states in real space suggests a route to probe them using photoemission, paving the way towards spectroscopic access to the quantum geometric tensor.
Conduction band structure and ultrafast dynamics of ferroelectric α-GeTe(111)
(2025) Kremer, Geoffroy; Nicolai, Laurent Christophe; Chassot, Frédéric; Maklar, Julian; Nicholson, Christopher W.; Dil, J. Hugo; Krempaský, Juraj; Springholz, Gunther; Ernstorfer, Ralph; Minár, Jan; Rettig, Laurenz; Monney, Claude
alpha-GeTe(111) is a noncentrosymmetric ferroelectric (FE) material for which a significative lattice distortion combined with a strong spin-orbit interaction gives rise to giant Rashba split states in the bulk and at the surface, which have been intensively probed in the occupied valence states using static angle-resolved photoemission spectroscopy (ARPES). Nevertheless, its unoccupied conduction band structure remains unexplored, in particular the experimental determination of its electronic band gap across momentum space. Using time-resolved ARPES based on high-repetition rate and extreme ultraviolet femtosecond (fs) laser, we unveil the band structure of alpha-GeTe(111) in the full Brillouin zone, both in the valence and conduction states, as well as the exploration of its out-of-equilibrium dynamics. Our work confirms the semiconducting nature of alpha-GeTe(111) with a 0.85 eV indirect band gap, which provides an upper limit for comparison to density functional theory calculations. We finally reveal the dominant scattering mechanisms of photoexcited carriers during the out-of-equilibrium dynamics under fs light pulses.
Effect of laser shock peening on the microstructure of GX4CrNi13-4 martensitic stainless steel
(2025) Bricín, David; Jansa, Zdeněk; Kaufman, Jan; Špirit, Zbyněk; Fulín, Zdeněk; Strejcius, Josef
This study investigates the effect of laser shock peening (LSP) on the microstructure and properties of GX4CrNi13-4 martensitic stainless steel. Three different conditions of surface preparation were examined in this study. First, a control group was left with a ground surface. The two remaining groups were treated with LSP. In one case, a single pass of LSP was applied and in the other case, a double pass of LSP was concerned. The samples were subsequently subjected to corrosion-fatigue testing in a water solution of 0.5 g/l NaCl, metallographic analysis, X-ray diffraction, and microhardness measurements. Experimental results of the corrosion-fatigue test showed that the LSP-treated samples exhibited fatigue cracking at higher force amplitude. Roughness measurements showed that the surface after LSP was rougher compared to the initial ground surface but with a lower proportion of grooves. Greater plastic surface deformation resulted in an increase in microhardness in the near-surface region, which was accompanied by an increase in the calculated density of geometrically necessary dislocations, a decrease in the proportion of retained austenite and coarsening of the martensite phase crystallite.
Emergence of a bandgap in nano-scale graphite: A computational and experimental study
(2025) Chaiyachad, Sujinda; Vo, Phuc; Jindata, Warakorn; Singsen, Sirisak; Eknapakul, Tanachat; Jaisuk, Chutchawan; Fevre, Patrick Le; Bertran, Francois; Lu, Donghui; Huang, Yaobo; Nakajima, Hideki; Liewrian, Watchara; Fongkaew, Ittipon; Minár, Jan; Meevasana, Worawat
Bandgaps in layered materials are critical for enabling functionalities such as tunable photodetection, efficient energy conversion, and nonlinear optical responses, which are essential for next-generation photonic and quantum devices. Gap engineering could form heterostructures with complementary materials like transition metal dichalcogenides or perovskites for multifunctional devices. Graphite, conventionally regarded as a gapless material, exhibits a bandgap of similar to 100 meV in nano-scale patterned highly oriented pyrolytic graphite (HOPG), as revealed by angle-resolved photoemission spectroscopy (ARPES) and Raman measurements. Our state-of-the-art calculations, incorporating photoemission matrix element effects, predict this bandgap with remarkable accuracy and attribute it to mechanical distortions introduced during patterning. This work bridges theory and experiment, providing the direct evidence of a tunable bandgap in HOPG. Beyond its fundamental significance, this finding opens new possibilities for designing materials with tailored electronic properties, enabling advancements in terahertz devices and optoelectronics.
Smart injectable hydrogels for periodontal regeneration: Recent advancements in biomaterials and biofabrication strategies
(2025) Yin, Bohan; Dodda, Jagan Mohan; Wong, Siu Hong Dexter; Deen, G. Roshan; Bate, Jeffrey S.; Pachauri, Abhishek; Shiroud Heidari, Behzad; Kovářík, Tomáš; Luo, Chi-An; Tsai, Shiao-Wen
Periodontitis is a globally prevalent chronic inflammatory disease that leads to periodontal pocket formation and eventually destroys tooth-supporting structures. Hence, the drastic increase in dental implants for periodontitis has become a severe clinical issue. Injectable hydrogel based on extracellular matrix (ECM) is highly biocompatible and tissue-regenerative with tailor-made mechanical properties and high payload capacity for in situ delivery of bioactive molecules to treat periodontitis. This therapeutic tool not only enhances the drug release efficiency and treatment efficacy but also reduces operation time. Nevertheless, it remains challenging to optimize the mechanical properties and intelligent control drug release rate of injectable hydrogels to achieve the highest therapeutic outcome. Literature precedent has shown the modulation of polymer backbones (synthetic polymers, natural polysaccharides, and proteins), crosslinking strategies, other bioactive constituents, and potentially the incorporation of nanomaterials that overall improve the desirable physiochemical and biological performances as well as biodegradability. In this review, we summarize the recent advances in the development, design, and material characterizations of common injectable hydrogels. Furthermore, we highlight cutting-edge representative examples of polysaccharide-, protein- and nanocomposite-based hydrogels that mediate regenerative factors and anti-inflammatory drugs for periodontal regeneration. Finally, we express our perspectives on potential challenges and future development of multifunctional injectable hydrogels for periodontitis.
Probing the semiconductor-Dirac-semimetal transition in Na-Sb-Bi alloys with x-ray Compton scattering
(2025) Pulkkinen, Aki Ismo Olavi; Kothalawala, Veenavee Nipunika; Suzuki, Kosuke; Barbiellini, Bernardo; Nokelainen, Johannes; Chiu, Wei-Chi; Singh, Bahadur; Lin, Hsin; Pandey, Alok K.; Yabuuchi, Naoaki; Tsuji, Naruki; Sakurai, Yoshiharu; Sakurai, Hiroshi; Minár, Jan; Bansil, Arun
We discuss electron redistribution during the semiconductor-to-Dirac semimetal transition in Na-Sb-Bi alloys using x-ray Compton scattering experiments combined with first-principles electronic structure modeling. A robust signature of the semiconductor-to-Dirac semimetal transition is identified in the spherically averaged Compton profile. We demonstrate how the number of electrons involved in this transition can be estimated to provide a novel descriptor for quantifying the strength of spin-orbit coupling responsible for driving the transition. The associated theoretical deviation of the Born charge of Na in Na3Bi from the expected ionic charge of +1 is found to be consistent with the corresponding experimental value of about 10%. Our study also shows the sensitivity of the Compton scattering technique toward capturing the spillover of Bi 6p relativistic states onto Na sites.
Trimetallic Alloys as an Electrocatalyst for Fuel Cells: The Case of Methyl Formate on Pt3Pd3Sn2
(2024) Yadav, Radhey Shyam; Kashyap, Diwakar; Pitussi, Itay; Gebru, Medhanie Gebremedhin; Teller, Hanan; Schechter, Alexander; Kornweitz, Haya
The shift toward renewable energy sources plays a central role in the quest for a circular economy. In this context, methyl formate (MF) has garnered attention as a compelling hydrogen carrier and alternative fuel, because of its remarkable characteristics (energy density, ease of storage and transport, and low boiling point). In this study, DFT calculations supported by online electrochemical mass spectroscopy (OE-MS) were performed to investigate the MF electro-oxidation (MFEO) on Pt3Pd3Sn2 (111). The DFT calculations provide insight into the role of Pt, Pd, and Sn atoms in MFEO. Pt and Pd together provide a preferred active site for initiating MFEO through the O-H bond scission, and Sn plays an essential role in the mitigation of CO through oxygenation or water activation. By comparing the reaction energies and activation barriers for all possible reactions in MFEO, the suggested path necessitates a minimum energy of 0.14 eV to initiate the MFEO. This value was supported by the experimental results, showing that the oxidation wave of MF starts at 0.15 V (70 degrees C). Density functional theory (DFT) results, supported by OE-MS, indicate that the hydrolysis of MF prior to MFEO is not preferred on Pt3Pd3Sn2 (111) surfaces, although the formation of methanol is plausible via a CH3O intermediate. Among the three small organic molecules (SOMs) studied-MF, methanol, and formic acid-MF has the lowest activation energy for the initial bond breaking that starts the whole oxidation process (0.13 eV), compared to formic acid (0.45 eV) and methanol (0.61 eV); thus, MF is the preferred fuel on Pt3Pd3Sn2 (111).
Kramers nodal lines in intercalated TaS2 superconductors
(2025) Zhang, Yichen; Gao, Yuxiang; Pulkkinen, Aki Ismo Olavi; Guo, Xingyao; Huang, Jianwei; Guo, Yucheng; Yue, Ziqin; Oh, Ji Seop; Moon, Alex; Oudah, Mohamed; Gao, Xue-Jian; Marmodoro, Alberto; Fedorov, Alexei; Mo, Sung-Kwan; Hashimoto, Makoto; Lu, Donghui; Rajapitamahuni, Anil; Vescovo, Elio; Kono, Junichiro; Hallas, Alannah M.; Birgeneau, Robert J.; Balicas, Luis; Minár, Jan; Hosur, Pavan; Law, Kam Tuen; Morosan, Emilia; Yi, Ming
Kramers degeneracy is one fundamental embodiment of the quantum mechanical nature of particles with half-integer spin under time reversal symmetry. Under the chiral and noncentrosymmetric achiral crystalline symmetries, Kramers degeneracy emerges respectively as topological quasiparticles of Weyl fermions and Kramers nodal lines (KNLs), anchoring the Berry phase-related physics of electrons. However, an experimental demonstration for ideal KNLs well isolated at the Fermi level is lacking. Here, we establish a class of noncentrosymmetric achiral intercalated transition metal dichalcogenide superconductors with large Ising-type spin-orbit coupling, represented by InxTaS2, to host an ideal KNL phase. We provide evidence from angle-resolved photoemission spectroscopy with spin resolution, angle-dependent quantum oscillation measurements, and ab-initio calculations. Our work not only provides a realistic platform for realizing and tuning KNLs in layered materials, but also paves the way for exploring the interplay between KNLs and superconductivity, as well as applications pertaining to spintronics, valleytronics, and nonlinear transport.

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