Temperature Dependence Research Articles

Influence of Temperature and Pressure on the Wetting Progress in 21700 Lithium‐Ion Battery Cells: Experiment, Model, and Lattice Boltzmann Simulation

AbstractThe electrolyte filling and subsequent wetting of the active material is a time‐critical process in the manufacturing of lithium‐ion batteries. Due to the metallic cell housing, the process phenomena are insufficiently accessible, preventing the replication of the wetting processes by mathematical or simulative methods and hindering efforts to accelerate the wetting process. Therefore, this publication employs a glass cell housing for electrolyte filling of a 21700 cylindrical cell to investigate the wetting at different temperatures and process pressures. In parallel, a mathematical replication of the wetting, as well as a lattice Boltzmann pore‐scale simulation, is used to evaluate the influence of these varying process boundary conditions. The results show a strong temperature dependence on electrolyte wetting and the positive effect of pressure changes in the wetting process. These findings are particularly relevant to the process design of large‐scale cylindrical cell manufacturing.

First-principles study on thermal and electrical transport properties of NbGe2 and NbSi2: the role of electron-phonon coupling

Abstract We study coupled electron and phonon transport in NbX2 with X=Ge, Si, in which experimental evidence of strong electron-phonon coupling and hydrodynamic transport has been reported. Based on first-principles calculations at the density functional theory level, we report their thermal and electrical transport properties. We find that phonon-electron scattering strongly affects their phonon thermal conductivity (κ ph) and leads to weak temperature dependence of κ ph, instead of normal inverse temperature dependence when anharmonic three phonon scattering dominates. Moreover, κ ph contributes to quarter of the total thermal conductivity, which differs from typical metals where total thermal conductivity is predominantly from electron part. Different from previous numerical study, our results of electrical resistivity agree well with experimental measurement. The anisotropic property of the transport coeffcients is attributed to the electron and phonon dispersion relation. Moreover, we find negligible effect of electron-phonon drag on the transport property, contrary to expectation from a strongly coupled electron-phonon fluid.

Temperature Dependence of Coherent versus Spontaneous Raman Scattering

Temperature Dependence of Coherent versus Spontaneous Raman Scattering

Spin injection from a magnetically near-compensated state in GdFeCo and inverse spin Hall effect in electron-hole compensated metal YH2.

Rare-earth-transition-metal (RE-TM) ferrimagnets are excellent materials for spin encode/decode operations via spin transport in nonmagnetic regions. This superior performance stems from two key factors. First, the antiferromagnetic coupling between RE4f and TM3d sublattices reduces both the spin-transfer-torque switching time and inter-device magnetic-coupling. Second, the RE-TM ferrimagnets function as spin injectors/ejectors, with the TM3d sublattice solely responsible for carrier spin polarization (p), similar to conventional ferromagnetic metals. We performed spin transport experiments using the sign change of p in RE-TM, which exhibits a positive value above the magnetization compensation temperature and a negative value below it. We measured temperature dependencies of the transverse resistances (RT) of electron-hole compensated metal YH2under out-of-plane spin-polarized current injection/ejection from GdFeCo (Gd:Fe:Co=25:66:9). The abrupt change in loop polarity of the out-of-plane field dependence of RT in YH2between 290 and 300 K, which aligns with the out-of-field curve of the polar Kerr rotation in GdFeCo electrodes, strongly suggests that the observed RT results from the inverse spin Hall effect (ISHE) in YH2. We analytically formulated ISHE in terms of the electron and hole spin currents injected from the spin sources, enabling regression analysis to assess the spin transport characteristics of a GdFeCo/YH2/GdFeCo magnetic double heterostructure. To explain the observed Hall voltages, enhancements in both the spin diffusion length of YH2and the spin injection efficiency are necessary.&#xD.

Gapped quantum spin liquid in a triangular-lattice Ising-type antiferromagnet PrMgAl11O19

In the search of quantum spin liquid (QSL), spin-1/2 triangular-lattice Heisenberg antiferromagnets have always been viewed as fertile soils. Despite the true magnetically ordered ground state, anisotropy has been considered to play a significant role in stabilizing a QSL state. However, the nature and ground state of the most anisotropic case, the triangular-lattice Ising antiferromagnet (TLIAF), remain elusive and controversial. Here, we report specific-heat and thermal-conductivity measurements on a newly discovered Ising-type QSL candidate PrMgAl11O19. At zero field, the magnetic specific heat shows a quadratic temperature dependence. On the contrary, no direct positive magnetic contribution to thermal conductivity is detected, ruling out the presence of mobile gapless fermionic excitations. Further analysis of phonon thermal conductivity reveals that the phonons are strongly scattered by thermally activated magnetic excitations out of a gap, which exhibits a linear dependence with magnetic field. These results demonstrate that the spin-1/2 TLIAF PrMgAl11O19 has a gapped Z2 QSL ground state. Published by the American Physical Society 2024

Proton irradiation Of Ga2O3 Schottky diodes and NiO/Ga2O3 heterojunctions.

p-NiO/n-Ga2O3 heterojunction (HJ) diodes exhibit much larger changes in their properties upon 1.1MeV proton irradiation than Schottky diodes (SDs) prepared on the same material. In p-NiO/Ga2O3 HJ diodes, the narrow region adjacent to the HJ boundary is found to contain a high density of relatively deep centers with levels near EC-0.17eV and a depleted region in the immediate vicinity of the HJ boundary. The series resistance of the HJ diodes is slightly higher than for the Schottky diodes and shows a temperature dependence with activation energy ~ 0.12eV, like the temperature dependence of the NiO film resistivity. Irradiation with 1.1MeV protons leads to a decrease of the hole concentration in the NiO, with a high carrier removal rate of ~ 1.3 × 105cm-1 and a strong compensation of the interfacial region where the concentration of the EC-0.17eV centers decreases with a high rate of ~ 7 × 103cm-1. The combined action of these two effects gives rise to the much stronger increase of the series resistance of the HJ diodes compared to Schottky diodes. The observed differences between the radiation response of the HJs and SDs cannot be credibly attributed to the changes of the density of any of the deep electron and hole traps detected in our experiments.

Bimolecular kinetics of Criegee intermediate (CH2OO) with 2-pentanone: experimental and theoretical analysis in atmospheric conditions.

Temperature-dependent kinetics of Criegee intermediate (CH2OO) with 2-pentanone were performed at 258-318 K and 50 Torr using pulsed laser photolysis-cavity ring-down spectroscopy (PLP-CRDS) technique. The measured room temperature rate coefficient was (3.84 ± 0.24) × 10-13 cm3 molecule-1 s-1. The reaction follows a negative temperature dependency, and the corresponding Arrhenius equation is k4 = (1.76 ± 0.36) × 10-15exp{(3.18 ± 0.11) kcal mol-1/RT}. The high-P limit rate coefficients obtained using CVT/SCT at CCSD(T)/aug-cc-pVTZ//B3LYP/6-311 + G(2df,2p) level of theory deviate from the experimental results, especially in the low-temperature region. At 258 K, the computed high-P limit rate coefficient exceeded the experimental value by more than a factor of four. Comparing all the reaction pathways, HCOOH was the major product formed in the title reaction. The atmospheric lifetime of 2-pentanone due to its reaction with CH2OO was calculated to be ~ 3000 days, rendering the reaction insignificant for inclusion in models of atmospheric 2-pentanone.

Optimization of Superconducting Niobium Nitride Thin Films via High-Power Impulse Magnetron Sputtering

Abstract We report a systematic comparison of niobium nitride thin films deposited on oxidized silicon substrates by reactive DC magnetron sputtering and reactive high-power impulse magnetron sputtering (HiPIMS). After determining the nitrogen gas concentration that produces the highest superconducting critical temperature for each process, we characterize the dependence of the critical temperature on film thickness. The optimal nitrogen concentration is higher for HiPIMS than for DC sputtering, and HiPIMS produces higher critical temperatures for all thicknesses studied. We attribute this to the HiPIMS process enabling the films to get closer to optimal stoichiometry before beginning to form a hexagonal crystal phase that reduces the critical temperature, along with the extra kinetic energy in the HiPIMS process improving crystallinity. We also study the ability to increase the critical temperature of the HiPIMS films through the use of an aluminum nitride buffer layer and substrate heating.

Engineering exchange bias at the interface of self-polarized ultrathin ferroelectric BaTiO3 and ferromagnetic La0.67Sr0.33MnO3

We investigate the emergence and optimization of conventional exchange bias (EB) in ultrathin (<10 nm) ferroelectric (FE) BaTiO3 (BTO)/ferromagnetic (FM) La0.67Sr0.33MnO3 (LSMO) epitaxial bilayers without an antiferromagnetic (AFM) material. The EB originates from the electronic orbital reconstruction at the FE-FM interface due to the ferroelectric polarization. We achieve maximum EB of approximately 42 Oe with single-domain polarization in nine-unit-cell-thick BTO, setting the BTO thickness above the critical threshold for ferroelectricity yet below the thickness of strain relaxation and multidomain breakdown. Furthermore, the LSMO layer needs to be thick enough to sustain both the FM layer and polarization-induced AFM spin configuration at the LSMO/BTO interface, yet as thin as possible to enable the EB loop shift. The temperature, training, field, and thickness dependence of the EB confirm that the LSMO/BTO interface exhibits conventional EB despite its unconventional origin. Using x-ray magnetic circular dichroism, scanning transmission electron microscopy, and density-functional-theory calculations, we confirm that the macroscopic EB effect originates from the interfacial AFM spin configuration in LSMO driven by FE-induced -orbital modifications in interfacial Mn ions. Thus, we engineer strong interfacial EB coupling in artificial multiferroics without a conventional AFM material by controlling FE polarization, highlighting the potential for advanced spintronic applications. Published by the American Physical Society 2024

Revised 4-Point Water Model for the Classical Drude Oscillator Polarizable Force Field: SWM4-HLJ.

In this work the 4-point polarizable SWM4 Drude water model is reparametrized. Multiple models were developed using different strategies toward reproduction of specific target data. Results indicate that no individual model can reproduce all the selected target data in the context of the present form of the potential energy function. The changes considered in the new models include, 1) variations in the gas phase dipole moment, 2) variations in the molecular polarizability, 3) variations of the distance between the oxygen and the M site, 4) variation of the oxygen Lennard-Jones (LJ) parameters, 5) introduction of a LJ potential to the hydrogen atoms, and 6) variations of the H-O-H angle. Detailed analysis is presented for 3 new water models from which a final model, SWM4-HLJ, is selected as the future default model for the Drude polarizable force field. The model maintains the gas phase dipole moment as the experimental value while the remaining listed terms were adjusted including a larger H-O-H angle (108.12). Compared to its predecessor, SWM4-NDP, the self-diffusion coefficient, water dimer properties, and water cluster energies are greatly improved. The temperature dependence of the density of the new model also performs better. Overall, the new SWM4-HLJ water model is a general improvement and a good balance between microscopic and bulk properties is achieved.

Synergistic Modeling of Liquid Properties: Integrating Neural Network-Derived Molecular Features with Modified Kernel Models.

A significant challenge in applying machine learning to computational chemistry, particularly considering the growing complexity of contemporary machine learning models, is the scarcity of available experimental data. To address this issue, we introduce an approach that derives molecular features from an intricate neural network-based model and applies them to a simpler conventional machine learning model that is robust to overfitting. This method can be applied to predict various properties of a liquid system, including viscosity or surface tension, based on molecular features drawn from the ab initio calculated free energy of solvation. Furthermore, we propose a modified kernel model that includes Arrhenius temperature dependence to incorporate theoretical principles and diminish extreme nonlinearity in the model. The modified kernel model demonstrated significant improvements in certain scenarios and possible extensions to various theoretical concepts of molecular systems.

Carbon accumulation model for simulating 14C radioactivity in Chinese yam grown from a seed bulbil.

Modeling carbon accumulation in crop plants is key to evaluating the transfer of atmospheric 14C into the edible parts of the plants growing near nuclear facilities. Chinese yam 'Nagaimo' (Dioscorea polystachya Turcz.) is a major crop cultivated near a spent nuclear fuel reprocessing plant in Rokkasho, Aomori, Japan. We developed a dynamic compartment model for assessing carbon and 14C accumulation in Chinese yam grown from a seed bulbil in the field. Light and temperature dependence of leaf photosynthesis and temperature dependence of respiration in leaves, stems and belowground parts (tuber and root) were incorporated into the model. Estimated amounts of carbon in the leaves, stems and belowground parts were good agreement with the measured data from the field. Simulation results of 14C accumulation using this model indicated that the accumulation of 14C in belowground parts at the harvest depends on the rate of photosynthesis on the day of exposure.

Splitting of triply quantized vortices in Bose-Einstein condensates of finite temperature

Abstract Utilizing the dissipative Gross-Pitaevskii equation, we investigated the splitting dynamics of triply quantized vortices at finite temperature. Through linear perturbation analysis, \textcolor{red}{we determined the excitation modes of these vortices across various dissipation parameters. We identified three unstable modes with $p=2, 3, $ and $4$ fold rotational symmetries, } revealing a significant dynamic transition of the most unstable mode. That is, as the dissipation parameter increases, the most unstable mode transitions from $p=2$ mode to $p=3$ mode. Throughout the entire range of dissipation parameters, the $p=4$ unstable mode is never the dominant mode. Subsequently, we performed nonlinear numerical simulations of the vortex splitting process. Under random perturbations, we confirmed the dynamical transition, and under specific perturbations, we confirmed the instability of the $p=4$ mode. Our findings on the finite temperature dependence of the splitting dynamics of triply quantized vortices are expected to be verifiable in experiments.

Understanding the relationship between preferential interactions of peptides in water-acetonitrile mixtures with protein-solvent contact surface area.

The influence of polar, water-miscible organic solvents (POS) on protein structure, stability, and functional activity is a subject of significant interest and complexity. This study examines the effects of acetonitrile (ACN), a semipolar, aprotic solvent, on the solvation properties of blocked Ace-Gly-X-Gly-Nme tripeptides (where Ace and Nme stands for acetyl and N-methyl amide groups respectively and X is any amino acid) through extensive molecular dynamics simulations. Individual simulations were conducted for each peptide, encompassing five different ACN concentrations within the range of χACN = 0.1-0.9. The preferential solvation parameter (Γ) calculated using the Kirkwood-Buff integral method was used for the assessment of peptide interactions with water/ACN. Additionally, weighted Voronoi tessellation was applied to obtain a three-way data set containing four time-averaged contact surface area types between peptide atoms and water/ACN atoms. A mathematical technique known as N-way Partial Least Squares (NPLS) was utilized to anticipate the preferential interactions between peptides and water/ACN from the contact surface areas. Furthermore, the temperature dependency of peptide-solvent interactions was investigated using a subset of 10 amino acids representing a range of hydrophobicities. MD simulations were conducted at five temperatures, spanning from 283 to 343K, with subsequent analysis of data focusing on both preferential solvation and peptide-solvent contact surface areas. The results demonstrate the efficacy of utilizing contact surface areas between the peptide and solvent constituents for successfully predicting preferential interactions in water/ACN mixtures across various ACN concentrations and temperatures.

Ti4Ir2O : A time reversal invariant fully gapped unconventional superconductor

Here we report muon spin rotation (μSR) experiments on the temperature and field dependence of the effective magnetic penetration depth λ(T) in the η-carbide-type suboxide Ti4Ir2O, a superconductor with a considerably high upper critical field. The temperature dependence of λ(T), obtained from transverse-field (TF)-μSR measurements, is in perfect agreement with an isotropic fully gaped superconducting state. Furthermore, our ZF μSR results confirm that the time-reversal symmetry is preserved in the superconducting state. We find, however, a remarkably small ratio of Tc/λ0−2∼1.22. This value is close to most unconventional superconductors, showing that a very small superfluid density is present in the superconducting state of Ti4Ir2O. The presented results will pave the way for further theoretical and experimental investigations to obtain a microscopic understanding of the origin of such a high upper critical field in an isotropic single-gap superconducting system. Published by the American Physical Society 2024

Structural, Solvent, and Temperature Effects on Protein Junction Conductance.

Cytochrome b562 is a small redox-active heme protein that has served as an important model system for understanding biological electron transfer processes. Here, we present a comprehensive theoretical study of electron transport mechanisms in protein-metal junctions incorporating cytochrome b562 using a multi-scale computational approach. Employing molecular dynamics (MD) simulations, we generated junction geometries for both vacuum-dried and solvated conditions, with the protein covalently bound to gold contacts in various configurations. Coherent tunneling, described by the Landauer-Buttiker formalism within the density functional theory (DFT) framework, is compared to the incoherent hopping charge transport mechanism captured by the semi-classical Marcus theory. The tunneling was identified as the dominant mechanism explaining the experimental data measured on the cytochrome b562 junctions, exhibiting exponential yet very shallow distance dependence. While the structural orientations and protein contacts with the electrodes influence the junction conductance significantly, the solvation effects are relatively small, affecting the electronic properties mostly via the adsorption arrangement. On the other hand, the considerable temperature dependence of the conductance was found strong only for hopping, while the tunneling current magnitudes remain practically unaffected and are a good indicator of the coherent mechanism in this case.

From germolane to germylenes: a theoretical DFT study of thermal decomposition pathways and reactivity

This study addresses the often-overlooked chemistry of germanium compared to the extensively researched carbon and silicon. Using advanced DFT methods, we investigated the thermal decomposition of germolane (germacyclopentane). The suggested mechanisms include a 1,2-H shift and 1,1-H2 elimination to form a pentacyclic germylene (1λ2-germolane). The other pathway involves a stepwise [3 + 2] cycloreversion to form a diradical followed by ethene and germirane. Under M062X/def2-TZVP level of theory, the activation barriers in terms of Gibbs energy (ΔG ‡ 298) for the 1,2-H shift and 1,1-H2 elimination pathways were 240.9 and 236.3 kJ/mol, respectively. The reaction energies (ΔG° 298) for the initiative steps in the 1,2-H shift and 1,1-H2 elimination mechanisms were 102.9 and 96.2 kJ/mol, indicating a thermodynamic and kinetic competition between the two routes. Temperature dependence analysis from 300 to 1200 K reveals that the 1,1-H2 elimination dominates at higher temperatures and is expected to become spontaneous above 1000 K.

Characterization of low sodium type II silicon clathrate film spin dynamics

Type II Si clathrate is a Si-based, crystalline alternative to diamond silicon with interesting optoelectronic properties. Here, a pulsed electron paramagnetic resonance study of the spin dynamics of sodium-doped, type II NaxSi136 silicon clathrate films is reported. Focusing on the hyperfine lines of isolated Na atoms, the temperature dependence of the electron spin dynamics is examined from 6 to 25 K. The measurements exhibit multi-exponential decay, indicating multiple spin relaxation rates in the system. As expected, spin relaxation time (T1) increases rapidly with decreasing temperature, reaching ∼300 μs at 6.4 K. The phase memory (TM) shows less temperature dependence with a value of ∼3 μs at the same temperature. The temperature dependence of T1 exhibits Arrhenius behavior in the measurement range consistent with an Orbach pathway. There are strong similarities to the spin behavior of other defect donors in diamond silicon. The results provide insights into the potential of Si clathrates for spin-based applications.

Suppression of symmetry-breaking correlated insulators in a rhombohedral trilayer graphene superlattice.

Counterintuitive temperature dependence of isospin flavor polarization has recently been found in twisted bilayer graphene, where unpolarized electrons in a Fermi liquid become a spin-valley polarized insulator upon heating. So far, the effect has been limited to v = +/-1 (one electron/hole per superlattice cell), leaving open questions such as whether it is a general property of symmetry-breaking electronic phases. Here, by studying a rhombohedral trilayer graphene/boron nitride moiré superlattice, we report that at v = -3 a resistive peak emerges at elevated temperatures or in parallel magnetic fields. Concomitantly, the Hall carrier density tends to reset at the integer filling, signaling spin-valley flavor symmetry breaking. These phenomena can also be observed at v = -1 and -2 when the displacement field is large enough to suppress correlated insulators at low temperatures. Our results greatly expand the scope for observing the counterintuitive temperature dependence of flavor polarization, i.e., the regimes proximal to symmetry-breaking phases where the flavor polarization order strongly fluctuates, encouraging more experimental and theoretical exploration of isospin flavor polarization dynamics in flat-band moiré systems.

Multisource energy harvesting using (Ba,Ca)(Zr,Ti)O3 oscillating under temperature gradient

AbstractThe concept of multisource energy harvesting has attracted attention in order to harvest multiple types of energy in a single material. In this work, Pb‐free (Ba,Ca)(Zr,Ti)O3 (BCZT) ceramics were used to investigate a combination of piezoelectric and pyroelectric energy harvesting behavior. The temperature dependence of the permittivity and the pyroelectric coefficient was measured, and the pyroelectric properties of BCZT were expected to improve near its orthorhombic–tetragonal phase transition temperature TO–T (∼40°C). The output voltage and current were measured using a BCZT plate, where the BCZT was oscillated under a temperature gradient to apply mechanical stress and temperature fluctuation simultaneously. The measured output voltage from the combined piezo‐ and pyroelectric contributions at a frequency of 2 Hz and with a load resistance of 10 MΩ was 1.4 times higher than the sole piezoelectric output voltage. The resulting combined output voltage was confirmed by finite element simulation.