Materials Science · Cross-listed from physics.chem-ph
Single-run determination of the saturation vapor pressure and enthalpy of vaporization/sublimation of a substance undergoing successive solid-solid and solid-liquid phase transitions: the case of $N$-methyl acetamide
Mohsen Salimi, Aurelien Dantan and Henrik B. Pedersen
We report on the dynamical measurement of the saturation vapor pressure of $N$-methyl acetamide in the temperature range $-30^\circ$C to $34^\circ$C. This is achieved by monitoring the pressure inside a
vacuum chamber in which a precooled sample of the substance slowly thermalizes to the chamber temperature, undergoing first a phase transition between two crystalline structures around $1^\circ$C and then a solid-
liquid phase transition around $30^\circ$C. Such a measurement provides in a single run accurate data for the saturation vapor pressure and the enthalpies of sublimation and vaporization of the different phases of the investigated substance.
Read the full abstract ▾
Materials Science · Cross-listed from physics.chem-ph
Unraveling Surface Chemistry of irreversible reduction of iron oxides through the Time-Resolved APXPS and Chemometrics
Mohammed Alaoui Mansouri, Manoj Ghosalya, Aidin Heidari et al. (+8 more)
This work presents a study on the application of Time-Resolved Ambient Pressure X-ray Photoelectron Spectroscopy (TR-APXPS) in association with chemometric techniques, specifically Principal Component Analysis (PCA) and Multivariate Curve Resolution with Alternating Least Squares (MCR-ALS), to investigate the surface chemistry and dynamics of Fe2O3 reduction processes. The use of TR-APXPS allows for real-time monitoring of chemical changes at the surface of Iron
oxides during reduction, providing valuable insights into the reaction mechanisms and kinetics involved. One key challenge in analyzing TR-APXPS data is the presence of overlapping peaks and complex spectral features, which can make accurate quantification and interpretation difficult. Traditional spectral fitting methods may struggle with these complexities and result in ambiguous or inaccurate results. However, the chemometric approaches are promising tools to overcome these challenges by extracting pure spectral profiles of individual chemical species and their temporal profiles from the complex and overlapping data. The results obtained from the TR-APXPS coupled with PCA and MCR-ALS analysis provide a detailed and precise understanding of the surface chemical changes during the Fe2O3 reduction. This includes identifying and following the formation of various intermediate species and their
evolution over time, which permits later to establish correlations between surface chemistry and process conditions. The integration of both chemometric tools in TR-APXPS data analysis not only addresses the challenges associated with complex spectral features, but also contributes to a deeper understanding of the underlying chemical changes and their dynamics. The obtained results have significant implications for process optimization, material synthesis, and tailoring of material properties for specific applications.
Read the full abstract ▾
All authors Mohammed Alaoui Mansouri, Manoj Ghosalya, Aidin Heidari, Yuzhao Wang, Mourad Kharbach, Anne Hietava, Mikko J. Sillanpää, Ilkka Launonen, Timo Fabritius, Marko Huttula, Samuli Urpelainen
Materials Science
Scalar and fully relativistic pressure and temperature-dependent ab-initio thermodynamics study of simple cubic polonium
Balaram Thakur, Xuejun Gong and Andrea Dal Corso
The ab-initio thermodynamic properties of simple cubic polonium ({\alpha}-Po) were studied within the quasi-harmonic approximation (QHA), where both
lattice vibrations (
phonons) and electronic excitations contributions are included in the Helmholtz free energy. We investigate the influence of
spin-orbit coupling (SOC) by comparing the scalar relativistic (SR) and fully relativistic (FR) pseudopotentials on the thermodynamic properties of polonium and evaluate the performance of three popular exchange-correlation functionals, GGA (PBE and PBEsol), and LDA (PZ). Temperature and pressure-dependent thermodynamic properties were compared with the available experimental and theoretical studies. We found that the effect of electronic excitations is negligible for all the thermodynamic properties. LDA+SOC provides a better agreement with the experimental volume, while the thermal expansion coefficients from LDA+SOC and PBEsol + SOC closely match experimental values. SOC effects appear insignificant for the isobaric heat capacity but substantially contribute to the adiabatic bulk modulus. The
phonon dispersions and mode-Grüneisen parameters ({\gamma}_q{\eta}) were interpolated at the
lattice constant corresponding to 301 K. The SR dispersions exhibit several anomalies in all directions, which were suppressed significantly by the inclusion of SOC. The role of SOC on the elastic constant-coefficient (C_ij) and elastic anisotropy factor at 0 K is also studied. The Pugh ratio confirmed that simple cubic polonium is ductile, and we observed that the elastic anisotropy factor and Pugh ratio decreased with increasing pressure. The effect of SOC on the Cauchy pressure is also determined.
Read the full abstract ▾
Materials Science
First-Principles Study of Mg-Induced Phase Stabilization in Ga$_2$O$_3$ polymorphs
Viswesh Prakash, Jingyu Tang, Lisa M. Porter et al. (+1 more)
In this study, we investigate the effect of Mg incorporation on the relative phase stability of the four primary Ga$_2$O$_3$ polymorphs using density functional theory (DFT) calculations, with the goal of rationalizing experimental observations suggesting that
diffusion from MgAl$_2$O$_4$ substrates contributes to relative stabilization of the $\gamma$ phase. Mg incorporation is modeled up to 25% of Ga sites within supercells derived from fully relaxed unit
cells of each polymorph. Our results show that while $\beta$-Ga$_2$O$_3$ remains the thermodynamically most stable phase, the enthalpic differences between polymorphs decrease with increasing Mg content. The inherently disordered $\gamma$ phase, with its high configurational
entropy, becomes less energetically unfavorable under Mg substitution, suggesting that
entropy-driven stabilization may facilitate its formation under high-temperature and/or nonequilibrium growth conditions such as those previously reported. These findings provide a thermodynamic rationale for the experimental observation of the $\gamma$ phase during epitaxial growth on MgAl$_2$O$_4$ spinel substrates.
Read the full abstract ▾
All authors Viswesh Prakash, Jingyu Tang, Lisa M. Porter, Rachel C. Kurchin
Materials Science · Cross-listed from physics.comp-ph
Bayesian identification of fibrous insulation thermal conductivity towards design of spacecraft thermal protection systems
Alex Alberts, Akshay Jacob Thomas, Kamran Daryabeigi et al. (+1 more)
The design of spacecraft thermal protection systems (TPS) requires accurate knowledge of thermal transport properties across wide ranges of temperature and pressure. For fibrous insulation, conventional measurement techniques in laboratory settings are typically limited to temperatures much lower than what is reached in atmosphere entry scenarios. Moreover, it is often the case that only temperature measurements are available, meaning that the thermal conductivity of the insulation must be indirectly inferred as an inverse problem. We propose a
Bayesian framework using information field theory (IFT) to reconstruct the thermal conductivity of high-temperature fibrous insulation from sparse experimental data. Under IFT, the conductivity is represented as a Gaussian process, and the physics is enforced via a physics-informed prior over the temperature derived from the heat equation. Bayes's rule produces an infinite-dimensional posterior distribution that quantifies uncertainty about the conductivity which can be evaluated in extrapolation regimes. We apply the method to Opacified Fibrous Insulation with both synthetic and experimental data to reconstruct the thermal conductivity beyond the experimental regime. The inferred conductivities are validated against reference data and then propagated into high-fidelity digital twins of flexible TPS performance under Mars and Earth entry trajectories. The results show that IFT yields accurate predictions with quantified uncertainty, enabling robust TPS sizing in regimes inaccessible to direct measurement.
Read the full abstract ▾
All authors Alex Alberts, Akshay Jacob Thomas, Kamran Daryabeigi, Ilias Bilionis
Materials Science
Controlling HER activity and stability of $\gamma$- and 6,6,12-Graphyne through engineered B-N doping: DFT and Reactive MD simulations
Juan Gomez Quispe, Matheus Medina, Subhendu Mishra et al. (+3 more)
Graphynes offer a chemically heterogeneous $sp/sp^{2}$ carbon framework with distinct electronic regimes and site-selective reactivity. Here, Density Functional Theory and Reactive Molecular Dynamics Simulations are combined to evaluate pristine, B-doped, N-doped, and B-N co-doped $\gamma$-graphyne and 6,6,12-graphyne (meta/ortho/para). $\gamma$-graphyne is a
semiconductor, while 6,6,12-graphyne exhibits an anisotropic Dirac-like semi-metallic dispersion. B/N substitution reconstructs near-$E_F$ states via dopant $\pi$ hybridization, and B-N pairing stabilizes defects through donor-acceptor compensation, with the ortho substitutions being the most favorable. Hydrogen adsorption remains weak on pristine
lattices but becomes locally optimized upon doping, with near thermo-neutral $\Delta G_{\mathrm{ads}}$ 'hot spots' predominantly on $sp$-proximate carbon sites adjacent to the dopants. Reactive MD at 300 K further reveals an activity stability trade-off: B-N ortho in $\gamma$-graphyne sustains controlled hydrogen uptake without catastrophic bond scission, whereas B-N meta/para degrade, and 6,6,12-graphyne is generally more susceptible to over-hydrogenation. These results identify the B-N geometry as a key design variable for graphyne-based HER catalysts, which require both a favorable $\Delta G_{\mathrm{ads}}$ and finite-temperature hydrogenation stability.
Read the full abstract ▾
All authors Juan Gomez Quispe, Matheus Medina, Subhendu Mishra, Douglas S Galvao, Abhishek Singh, Pedro Alves da Silva Autreto
Materials Science · Cross-listed from cond-mat.mes-hall
Demonstration of a Field-Effect Three-Terminal Electronic Device with an Electron Mobility Exceeding 40 Million cm^2/(Vs)
T. J. Martz-Oberlander, B. Bulgaru, Z. Berkson-Korenberg et al. (+6 more)
We report the fabrication and operation of a source-drain-gate three-terminal field-effect electronic device with an electron mobility exceeding $40\times 10^6$ cm$^2$ / (Vs). Several devices were fabricated, with the highest achieved electron mobility obtained using a symmetrically-doped GaAs/AlGaAs
quantum well forming a two-dimensional electron gas (2DEG) with a density of $1.47(1) \times 10^{11}$ cm$^{-2}$ and a pristine, pre-fabrication electron mobility of $44(2) \times 10^6$ cm$^2$/(\text{Vs}). To circumvent the well-known degradation of electron mobility during fabrication, devices were fabricated using a flip-chip technique where all lithographic processing steps were performed on a separate sapphire substrate. This method demonstrates the successful operation of various gate assembly designs on distinct 2DEGs without observable mobility degradation. This advance doubles the previous record for field-effect electronic device mobility and enables access to new regimes of
quantum transport and applications that were previously unfathomable due to mobility limitations.
Read the full abstract ▾
All authors T. J. Martz-Oberlander, B. Bulgaru, Z. Berkson-Korenberg, Q. Hawkins, K.W. West, K.W. Baldwin, A. Gupta, L. N. Pfeiffer, G. Gervais
Materials Science · Cross-listed from cond-mat.supr-con
Divergent Pressure Response of Superconductivity in Sc$_{6}$MTe$_{2}$ ($M$ = Fe, Ru and Ir)
J.N. Graham, S.S. Islam, K. Yuchi et al. (+7 more)
Identifying and understanding non-BCS superconductivity remains a central challenge in condensed-matter physics. Here we focus on the Sc$_{6}$MTe$_{2}$ family (M =d-electron metal), which provides a unique platform of isostructural compounds exhibiting superconductivity across 3d, 4d, and 5d systems. Using hydrostatic pressure as an additional tuning parameter,
muon-
spin rotation (${\mu}$SR) and AC susceptibility measurements uncover strongly contrasting pressure responses of superconductivity across the Sc$_{6}$MTe$_{2}$ series. The superconducting transition temperature, $T_{\rm C}$ decreases under pressure in the 3d Fe-based compound but increases for the 4d Ru- and 5d Ir-based systems, with the Ru compound showing the largest enhancement of nearly 50% within 2 GPa. The superfluid density exhibits similarly distinct pressure dependences, remaining nearly pressure independent for Fe while decreasing with increasing pressure for Ru and Ir. This suggests fundamentally different correlations between $T_{\rm C}$ and the superfluid density. Together, these results indicate that superconductivity emerging from strongly correlated and
spin-orbit-dominated regimes in Sc$_{6}$MTe$_{2}$ is likely governed by different microscopic mechanisms and offer a useful experimental basis for future microscopic theoretical studies.
Read the full abstract ▾
All authors J.N. Graham, S.S. Islam, K. Yuchi, P. Král, O. Gerguri, S. Huber, J. Chang, R. Khasanov, Y. Okamoto, Z. Guguchia
Materials Science
Competition between clustering and dispersion of cobalt atoms on perovskite surfaces: SrTiO3(001) and KTaO3(001)
Aji Alexander, Pankaj Kumar Samal, Llorenc Albons et al. (+8 more)
Perovskite
oxides are attractive for reactions in photo/electrocatalytic schemes, and extrinsic doping is a common strategy for tuning their properties. It is widely known that extrinsic dopants impact the structure and stability of perovskite surfaces, but an atomic-scale view is missing. Here, noncontact atomic force microscopy (ncAFM) and photoelectron spectroscopy (XPS/PES) are used to combine microscopic and spectroscopic evidence of cobalt adsorption, incorporation, and clustering at surfaces of two prototypical perovskites SrTiO3 and KTaO3. A number of different sub-ML coverages and temperatures of annealing were investigated. Several common features are observed: cobalt shows a strong preference for ionic nature (+2 and +3 charge states), and remains dispersed as single atoms to a certain extent in both perovskites. Two competing mechanisms are observed upon annealing: coalescence into clusters with a mixed metallic/ionic character, and incorporation into the surface and subsurface regions. The latter is more pronounced in SrTiO3, where a cobalt-stabilized surface reconstruction is identified, whereas for KTaO3 cobalt likely incorporates in the near-surface region.
Read the full abstract ▾
All authors Aji Alexander, Pankaj Kumar Samal, Llorenc Albons, Jesus Redondo, Jan Skvara, Igor Pis, Lukas Fusek, Josef Myslivecek, Viktor Johanek, Dominik Wrana, Martin Setvin
Materials Science
Biphasic Meniscus Coating for Scalable and Material Efficient Quantum Dot Films
Shlok Joseph Paul, Letian Li, Zheng Li et al. (+4 more)
Colloidal
quantum dots (cQDs) have emerged as a cornerstone of next-generation optoelectronics, offering unparalleled spectral tunability and solution-processability. However, the transition from laboratory-scale devices to sustainable industrial manufacturing is fundamentally hindered by
spin-coating workflows, which are intrinsically wasteful and restricted to planar geometries. These limitations are particularly acute for high-performance cQDs containing regulated elements such as lead, cadmium, or mercury, where poor material utilization exacerbates both environmental burden and cost. Here we report a biphasic dip-coating strategy that redefines the material efficiency of nanocrystal film fabrication. By utilizing an immiscible underlayer to displace ~88% of the active reservoir volume, we demonstrate a deposition geometry that decouples material consumption from total precursor volume. Infrared PbS photodetectors fabricated via this approach maintain their performance against
spin-coated
benchmarks while reducing ink consumption by up to 20-fold. Our technoeconomic analysis reveals that this biphasic architecture achieves cost parity at film thicknesses an order of magnitude lower than conventional monophasic dip-coating. Our results establish a low-waste framework for solution-processed materials, providing a viable pathway for the resource-efficient manufacturing of optoelectronic devices.
Read the full abstract ▾
All authors Shlok Joseph Paul, Letian Li, Zheng Li, Andrew Kim, Mia Klopfestein, Stephanie S. Lee, Ayaskanta Sahu
Materials Science
Exceptionally high carrier mobility in hexagonal diamond
Zirui He, Shang-Peng Gao and Meng Chen
Hexagonal diamond (h-diamond), or Lonsdaleite, is a promising wide-bandgap
semiconductor known for its high thermal conductivity and hardness. Based on ab initio calculations, we demonstrate its exceptionally high carrier mobilities. At room temperature, the hole mobilities along the $\perp c$ and $\parallel c$ directions are 6000 and 6024 cm$^{2}$V$^{-1}$s$^{-1}$, respectively, while the corresponding electron mobilities reach 12339 and 28473 cm$^{2}$V$^{-1}$s$^{-1}$. These values are significantly superior to those of most known
semiconductors, including cubic diamond. The small effective masses in h-diamond are comparable to those in the cubic phase, which cannot explain its substantially higher mobilities. Instead, two underlying mechanisms are uncovered. First, selection rules enforced by the
symmetry of h-diamond significantly suppress scattering, particularly for transverse acoustic
phonons, which predominate in the cubic phase around room temperature. Secondly, the spatial mismatch between the electronic wavefunctions and
phonon-induced scattering potentials leads to real-space electron-
phonon decoupling, which manifests as the suppression of out-of-plane polarised longitudinal acoustic scattering for holes, and a systematic weakening of acoustic scattering for electrons.
Read the full abstract ▾
Materials Science
Resolving the band alignment of InAs/InAsSb mid-wave-infrared type-II superlattices
Michał Rygała, Julian Zanon, Andreas Bader et al. (+5 more)
In this work, three InAs/InAs$_{0.65}$Sb$_{0.35}$ superlattices with different periods were investigated using photoluminescence and photoreflectance measurements and their band structure was simulated using a 14 bulk-band kp model. The structures were studied by analyzing the
evolution of the spectral features in temperature and excitation power to determine the origin of optical transitions. After identifying which of these are related to the superlattice mini-bands, a rich collection of observed higher-order optical transitions was compared with refractive-index calculations. This procedure was used to adjust the parameters of the theoretical model, namely the bowing parameters of the InAsSb valence band offset and bandgap. It was also shown that the spectroscopy of the higher-order states combined with numerical modeling of the refractive index is a powerful tool for improvement of the material parameters, presenting a new approach to material studies of advanced
semiconductor heterostructures.
Read the full abstract ▾
All authors Michał Rygała, Julian Zanon, Andreas Bader, Tristan Smołka, Fabian Hartmann, Sven Höfling, Michael Flatté, Marcin Motyka
Materials Science · Cross-listed from cond-mat.soft
Coupled gas and bubble dynamics at the solidification front
Bastien Isabella, Cécile Monteux and Sylvain Deville
The formation and entrapment of gas bubbles during solidification significantly influence the microstructure and mechanical properties of materials, from metallic
alloys to ice. While gas segregation at the solidification front is well-documented, the real-time dynamics of bubble nucleation, growth, and engulfment-and their dependence on solidification velocity-remain poorly understood. In this study, we use in situ cryo-confocal fluorescence microscopy to investigate the coupled gas-bubble dynamics at the solidification front of carbonated water, systematically varying the solidification velocity ($V = 1-20 \mu m/s$) while maintaining a constant thermal gradient ($G = 15 K/mm$). Our experiments reveal that bubble nucleation is governed by a characteristic nucleation time, which emerges from the interplay between gas
diffusion ahead of the front, nucleation kinetics, and bubble growth, all competing with the advancing solidification front. These results allow us to estimate the critical gas concentration for bubbles nucleation in carbonated water. These results offer a detailed understanding of the mechanisms controlling bubble nucleation and entrapment during solidification at constant thermal gradient. They contribute to the development of strategies to control bubble formation in industrial processes where the presence of bubbles can either be detrimental or intentionally harnessed.
Read the full abstract ▾
Materials Science
A General Theory of Chiral Splitting of Magnons in Two-Dimensional Magnets
Yu Xie, Dinghui Wang, Chao Li et al. (+2 more)
Magnons in antiferromagnets exhibit two
chiral modes, providing an intrinsic degree of freedom for
magnon-based computing architectures and spintronic devices. Electrical control of
chiral splitting is crucial for applications, but remains challenging. Here, we propose the concept of extrinsic
chiral splitting, involving alternating and ferrimagnet-like types, which can be induced and controlled by an electric field. A
symmetry framework based on 464 collinear
spin layer groups is established to classify
chiral splitting characteristics and electric field responses in two-dimensional magnets. We further elucidate how the
spin layer group determines the type of alternating
chiral splitting and the dominant lowest-order
magnetic exchange interaction. We demonstrate electric-field control over the magnitude and sign of the
chiral splitting, enabling control of the
spin Seebeck and Nernst effects related to thermal
spin transport. This work provides a general theory for electric field manipulation of
magnon chirality, paving the way for low-power magnonic logic devices.
Read the full abstract ▾
All authors Yu Xie, Dinghui Wang, Chao Li, Xiaofan Shen, Junting Zhang
Materials Science
Quasisymmetry Enriched Gapless Criticality at Chern Insulator Transitions
Jiayu Li, Feng-Ren Fan and Wang Yao
In continuous topological phase transitions (CTPTs), the low-energy physics is governed by gap-closing subspaces, where approximate "higher"
symmetries, termed quasisymmetries, may emerge. Here, we introduce the notion of quasisymmetry enrichment of these transitions. Focusing on paradigmatic normal-to-Chern
insulator transitions, we identify quasisymmetries in the gapless subspaces, which subdivide CTPTs of the same universality class according to quasisymmetry charges. Gapless criticalities with nontrivial charges exhibit regulated phenomena, including intrinsic correlations between charge and pseudospin currents and continuous generalized
Hall conductivities governed by the generalized Středa formula, both conventionally exclusive to gapped phases. These features arise as quasisymmetry forbids certain
matrix elements, rendering the generalized Berry
curvature integrable. By establishing quasisymmetry as a fundamental classifying ingredient, our work adds a new dimension for understanding the rich landscape of
quantum phase transitions.
Read the full abstract ▾
Materials Science
Pristine and Doped MoS2 Monolayers as Potential HCN Gas Sensors: A DFT Study
Neeraj Thakur, Anjna Bhardwaj, Arun Kumar et al. (+1 more)
Two-dimensional transition metal dichalcogenides (TMDCs) have been extensively investigated due to their tunable properties. In this work, density functional theory (DFT) is employed to investigate the adsorption behavior and sensing characteristics of HCN on pristine and doped MoS2 monolayers (X-MoS2, where X = P, N, Si, Al, B, Cl). The structural, electronic, and optical characteristics of all systems are examined to study the sensing properties of various doped MoS2 monolayers. In particular, the Al-MoS2 system demonstrates the strongest adsorption characterized by chemisorption, while the remaining systems show interactions of physisorption type. Recovery time and changes in electronic and optical properties reveal that Si-MoS2 possesses an ultrafast response of the order of microseconds, while Al-MoS2 exhibits a significantly longer recovery time, making it unsuitable for reusable sensors. P-MoS2, Si-MoS2, and Al-MoS2 monolayers show pronounced changes in their properties after HCN adsorption. To explore tunability in adsorption strength and recovery behavior, systems with two and three dopant atoms are further studied for P, Si, and Al doping. The results indicate that double doping enhances adsorption strength, whereas triple symmetric doping weakens it. Based on adsorption energy, recovery time, and electronic response, 2P-MoS2 and 3Al-MoS2 are identified as promising candidates for electrochemical and chemiresistive sensing of HCN. Additionally, the observed optical response in the ultraviolet region highlights their potential in UV-range optical sensor design.
Read the full abstract ▾
All authors Neeraj Thakur, Anjna Bhardwaj, Arun Kumar, Amarjeet Singh