Temperature Dependence Research Articles

Reduced thermal conductivity and enhanced TE performance in CrSb2via Fe-Bi co-substitution.

The efficiency of thermoelectric (TE) technology relies on the performance of TE materials. Substitution with heavy elements is an effective strategy in TE for enhancing phonon scattering without much affecting electrical transport properties. However, selecting suitable dopants to achieve a high TE figure-of-merit (ZT) poses a significant challenge. Thus, in this study, the efficacy of combined (Fe and Bi) co-substitution in CrSb2is investigated as a promising strategy to enhance ZT by lowering thermal conductivity. A series of co-substituted Cr1-xFexBiySb2-y(x= 0, 0.25, 0.50, 0.75, 1 andy= 0.10, 0.15, 0.20,0.25) samples were synthesized via furnace reaction followed by spark plasma sintering technique. Phase analysis and temperature dependence TE transport properties were systematically studied on synthesized samples. Furthermore, to analyze the impact of disorder induced by Bi/Fe substitution, electronic structure calculation was performed using the projector augmented-wave method. Notably, Cr0.75Fe0.25Bi0.15Sb1.85exhibited a low thermal conductivity of ∼2.5 W m-1K-1at 300 K, which reduced to half compared to that of pristine CrSb2(∼5 W m-1K-1). This reduction is attributed to the introduction of significant mass fluctuations and point defects along with the presence of Bi at grain boundaries by co-substitution. Consequently, a remarkable 90% enhancement inZT(∼0.021) at 350 K was achieved for Cr0.75Fe0.25Bi0.15Sb1.85compared to that of pristine CrSb2(ZT∼ 0.012). This study can provide valuable insights into the rational design of effective dopants in other TE materials also.

Temperature dependence of spatial nanoheterogeneities of shear modulus in supercooled glycerol.

The boson peak in the terahertz vibrational spectrum carries information about nano-heterogeneities in the shear modulus in glass formers. Its evolution upon heating or cooling in a supercooled liquid state may shed light on the temperature dependence of heterogeneities. For this purpose, an analysis of the light scattering spectra of supercooled glycerol in the spectral range of the boson peak and fast relaxation was carried out and the parameters of the boson peak in the temperature range 180-330K were determined. The temperature dependent frequency of the boson peak was then expressed in terms of the mean-square amplitude of the shear modulus fluctuations. This was done using the heterogeneous elasticity theory in combination with the perturbation theory on small fluctuations and Ioffe-Regel criterion for transverse vibrations in glass formers. The contribution of structural relaxation effects to phonon damping becomes significant with increasing temperature. It is shown here that structural relaxation largely determines the temperature dependence of the mean-square fluctuations of the shear modulus at high temperatures. By solving the inverse problem, the temperature dependence of shear modulus fluctuations was obtained. It shows a rapid decrease above ∼250K with a linear extrapolation going to zero at the so-called Arrhenius temperature TA = 350K. Comparison with literature data on the Landau-Placzek ratio shows that they have a similar temperature dependence at T < TA, which is explained by the appearance of nanometer scale spatial heterogeneities below TA. This is confirmed by the temperature dependence of the amplitude of the boson peak.

Roles of H-Bonding and Hydride Solvation in the Reaction of Hydrated (Di)electrons with Water to Create H2 and OH.

Even though single hydrated electrons (ehyd-'s) are stable in liquid water, two hydrated electrons can bimolecularly react with water to create H2 and hydroxide: ehyd- + ehyd- + 2H2O → H2 + 2OH-. The rate of this reaction has an unusual temperature and isotope dependence as well as no dependence on ionic strength, which suggests that cosolvation of two electrons as a single hydrated dielectron (e2,hyd2-) might be an important intermediate in the mechanism of this reaction. Here, we present an ab initio density functional theory study of this reaction to better understand the potential properties, reactivity, and experimental accessibility of hydrated dielectrons. Our simulations create hydrated dielectrons by first simulating single ehyd-'s and then injecting a second electron, providing a well-defined time zero for e2,hyd2- formation and offering insight into a potential experimental route to creating dielectrons and optically inducing the reaction. We find that e2,hyd2- immediately forms in every member of our ensemble of trajectories, allowing us to study the molecular mechanism of H2 and OH- formation. The subsequent reaction involves separate proton transfer steps with a generally well-defined hydride subintermediate. The time scales for both proton transfer steps are quite broad, with the first proton transfer step spanning times over a few ps, while the second proton transfer step varies over ∼150 fs. We find that the first proton transfer rate is dictated by whether or not the reacting water is part of an H-bond chain that allows the newly created OH- to rapidly move by Grotthuss-type proton hopping to minimize electrostatic repulsion with H-. The second proton transfer step depends significantly on the degree of solvation of H-, leading to a wide range of reactive geometries where the two waters involved can lie either across the dielectron cavity or more adjacent to each other. This also allows the two proton transfer events to take place either effectively concertedly or sequentially, explaining differing views that have been presented in the literature.

Exploring Phase Transition and Structural Complexity in the Mixed Cation Uranium Oxide CaUNb2O8.

The structures and high-temperature phase transition of CaUNb2O8 were studied in situ using synchrotron X-ray and neutron powder diffraction. Rietveld refinements provided an accurate description of the crystal structures of both the monoclinic fergusonite-type I2/b structure observed at room temperature and the tetragonal scheelite-type I41/a structure found at high temperatures. Bond valence sum analysis showed Nb5+ to be octahedrally coordinated in the monoclinic fergusonite-type structure, akin to other ANbO4 materials. Rietveld analysis of the variable temperature data allowed for the determination of accurate unit cell parameters and atomic coordinates, as well as revealing a reversible phase transition around ∼750 °C. The Nb-O bond distances display anomalous behavior, with a discontinuity in the longer Nb-O(1') distance coinciding with the phase transition suggestive of a reconstructive phase transition. Mode analysis identified the Γ2+ mode as the primary mode that drives the phase transition; this is linearly coupled to the induced spontaneous strain within the monoclinic fergusonite-type structure. Analysis of the temperature dependence of the Nb(z) positional parameter, as well as of the ϵ1-ϵ2 and ϵ6 strain parameters, showed that the phase transition is not strictly second order, with the critical exponent β ≠ 1/2. This study demonstrates the complex structural features of mixed cation metal oxides at elevated temperatures.

Diffusion and structure of propylene carbonate-metal salt electrolyte solutions for post-lithium-ion batteries: From experiment to simulation.

The diffusion of cations in organic solvent solutions is important for the performance of metal-ion batteries. In this article, pulsed field gradient nuclear magnetic resonance experiments and fully atomistic molecular dynamic simulations were employed to study the temperature-dependent diffusive behavior of various liquid electrolytes representing 1M propylene carbonate solutions of metal salts with bis(trifluoromethylsulfonyl)imide (TFSI-) or hexafluorophosphate (PF6-) anions commonly used in lithium-ion batteries and beyond. The experimental studies revealed the temperature dependence of the diffusion coefficients for the propylene carbonate (PC) solvent and for the anions following an Arrhenius type of behavior. It was observed that the PC molecules are the faster species. For the monovalent cations (Li+, Na+, K+), the PC solvent diffusion was enhanced as the cation size increased, while for the divalent cations (Mg2+, Ca2+, Sr2+, Ba2+), the opposite trend was observed, i.e., the diffusion coefficients decreased as the cation size increased. The anion diffusion in LiTFSI and NaTFSI solutions was found to be similar, while in electrolytes with divalent cations, a decrease in anion diffusion with increasing cation size was observed. It was shown that non-polarizable charge-scaled force fields could correspond perfectly to the experimental values of the anion and PC solvent diffusion coefficients in salt solutions of both monovalent (Li+, Na+, K+) and divalent (Mg2+, Ca2+, Sr2+, Ba2+) cations at a range of operational temperatures. Finally, after calculating the radial distribution functions between cations, anions, and solvent molecules, the increase in the PC diffusion coefficient established with the increase in cation size for monovalent cations was clearly explained by the large hydration shell of small Li+ cations, due to their strong interaction with the PC solvent. In solutions with larger monovalent cations, such as Na+, and with a smaller solvation shell of PC, the PC diffusion is faster due to more liberated solvent molecules. In the salt solutions with divalent cations, both the anion and the PC diffusion coefficients decreased as the cation size increased due to an enhanced cation-anion coordination, which was accompanied by an increase in the amount of PC in the cation solvation shell due to the presence of anions.

Governing of the piezoelectric effect by external fields and strains

Piezoelectricity in quantum rare-earth metallic boron oxides with the coupling between magnetic, electric and elastic subsystem is studied theoretically. It is proved that the change of piezoelectric modules of the considered crystals are proportional to components of the quadrupole susceptibility, which determines the external magnetic and electric fields, strain and temperature dependences of that change. We show why holmium compounds manifest the strongest renormalization among other rare-earth ions in this family of crystals. The reason is in the structure of the low energy term of the electron configuration, depending on spins and orbital moments of 4f electrons.

Elevation-dependent biases of raw and bias-adjusted EURO-CORDEX regional climate models in the European Alps

AbstractData from the EURO-CORDEX ensemble of regional climate model simulations and the CORDEX-Adjust dataset were evaluated over the European Alps using multiple gridded observational datasets. Biases, which are here defined as the difference between models and observations, were assessed as a function of the elevation for different climate indices that span average and extreme conditions. Moreover, we assessed the impact of different observational datasets on the evaluation, including E-OBS, APGD, and high-resolution national datasets. Furthermore, we assessed the bi-variate dependency of temperature and precipitation biases, their temporal evolution, and the impact of different bias adjustment methods and bias adjustment reference datasets. Biases in seasonal temperature, seasonal precipitation, and wet-day frequency were found to increase with elevation. Differences in temporal trends between RCMs and observations caused a temporal dependency of biases, which could be removed by detrending both observations and RCMs. The choice of the reference observation datasets used for bias adjustment turned out to be more relevant than the choice of the bias adjustment method itself. Consequently, climate change assessments in mountain regions need to pay particular attention to the choice of observational dataset and, furthermore, to the elevation dependence of biases and the increasing observational uncertainty with elevation in order to provide robust information on future climate.

Comparison of Machine Learning Approaches for Prediction of the Equivalent Alkane Carbon Number for Microemulsions Based on Molecular Properties.

The chemical properties of oils are vital in the design of microemulsion systems. The hydrophilic-lipophilic difference equation used to predict microemulsions' phase behavior expresses the oils' physiochemical properties as the equivalent alkane carbon number (EACN). The experimental determination of EACN requires knowledge of the temperature dependence of the microemulsion system and the effects of different surfactant concentrations. Thus, the experimental determination is time-intensive and tedious, requiring days to months for proper separations. Furthermore, the experiments require high purity of chemicals because microemulsions are sensitive to impurities. Our work focuses on the quick and reliable predictions of the EACN with machine learning (ML) models. Due to the immaturity of ML chemical predictions, we compare three graph neural networks (GNNs) and a gradient-boosted tree algorithm, known as XGBoost. The GNNs use the molecular structures represented as simplified molecular-input line-entry system (SMILES) codes for the initial input, which allows us to assess whether geometry optimization is necessary for reliable results. The XGBoost model also begins with the SMILES representations of the molecules but uses molecular descriptors instead of geometry optimizations. The best model tested (crystal graph convolutional neural network with Merck molecular force field-94) has an error of 1.15 EACN units of the true EACN for unknown data with the errors skewed toward zero and an R2 score of 0.9.

Cold Recycling Technology for Airfield Pavement Rehabilitation Practices

Cold recycling technology has recently achieved significant success in highway maintenance and construction applications. In this study, the potential of incorporating emulsion-based cold recycled layers into airfield pavement design is explored. The permanent deformation resistance of cold recycled (CR) mixtures was characterized under various stress states and loading conditions to provide a realistic representation of the loads induced by aircraft tires on typical airfield pavement structures. Finite element modeling simulations of several airfield structures incorporating a CR layer were leveraged to derive the triaxial stress states induced by the moving load of various aircraft tires on the CR layer. A mix design was developed using a common approach. The simulated stress states were then projected and applied to the developed mix design in triaxial compression repeated load permanent deformation experiments. The influence of time and temperature dependence of the material on permanent deformation was also studied. The experiment highlighted the sensitivity of the mixture to tire pressure, surface layer thickness, vehicle speed, and temperature. The results indicate that the selection of cold recycling applications for airfield pavement should account for the unique site-specific conditions and the structural composition of the pavement where the CR layer will be incorporated. The evident viscoplastic characteristics in CR mixtures in the triaxial repeated load experiments highlighted the importance of considering them in the structural design of the CR layer.

Differing temperature dependencies of functional homologs zebrafish Abcb4 and human ABCB1

The ATP binding cassette (ABC) transporters human ABCB1 and zebrafish (Danio rerio) Abcb4 are functionally homologous multixenobiotic/multidrug (MXR/MDR) efflux transporters that confer the efflux of a broad range of diverse chemical compounds from the cell. As ATPases, the transporters utilize the energy released by ATP cleavage for protein conformation changes and concomitant active transport of substrate compounds. The temperatures, at which human ABCB1 and zebrafish Abcb4 need to function, can substantially differ: Whereas the ambient temperature of human ABCB1, which is that of the human body, is constant, zebrafish Abcb4 has to be active in a wider temperature range as the body temperature of zebrafish can considerably vary, depending on the ambient water temperature (18°C–40°C). Here, we examined the effect of temperature on the ATPase activities of recombinant human ABCB1 and zebrafish Abcb4 generated with the baculovirus expression system. Incubation temperatures for enzyme reactions were set to 37°C and 27°C, corresponding to the human body temperature and the cultivation temperature of zebrafish in our lab, respectively. For stimulation and inhibition of zebrafish Abcb4 and human ABCB1 ATPase activities verapamil and cyclosporin A were added at different concentrations and 50% effect concentrations (EC50) were determined. The different temperatures had a stronger effect on the human ABCB1 than on the zebrafish Abcb4 ATPase: Differences between EC50 values for verapamil at 37°C and 27°C, respectively, were 1.8-fold for human ABCB1 but only 1.2-fold for zebrafish Abcb4. Activation energies (Ea) of basal and verapamil-stimulated ATPases, calculated based on the Arrhenius equation, were 2-fold (basal) and 1.5-fold (verapamil-stimulated) higher for human ABCB1 than for zebrafish Abcb4. The differences between zebrafish Abcb4 and human ABCB1 ATPases in temperature sensitivity and activation energy could be important for the comparison of the functional properties of the two transporter proteins in the context of pharmaco-/toxicokinetics. Related to this, our finding that at equal reaction conditions the zebrafish Abcb4 ATPase activity tended to be generally higher than that of human ABCB1 may also be important, as this may point to a higher substrate compound transport rate of Abcb4.

Exploring Green Fluorescent Protein Brownian Motion: Temperature and Concentration Dependencies Through Luminescence Thermometry

AbstractLuminescent nanothermometry emerges as a powerful tool for studying protein dynamics. This technique was employed to perform the first measurement of the temperature dependence of protein Brownian velocity, showcasing the illustrative example of enhanced green fluorescent protein (EGFP) across physiologically relevant temperatures (30−50 °C) and concentrations (40, 60, and 80 × 10−3 kg m−3). EGFP exhibited a concentration‐dependent decrease in Brownian velocity, from (1.47 ± 0.09) × 10−3 m s−1 to (0.35 ± 0.01) × 10−3 m s−1, at 30 °C, mimicking crowded cellular environments. Notably, the protein Brownian velocity increased linearly with temperature. These results demonstrate the suitability of concentrated suspensions for modeling intracellular crowding and validate luminescent nanothermometry for protein Brownian motion studies. Furthermore, the observed linear relationship between the logarithm of the protein Brownian velocity and concentration indicates that EGFP motion is not primarily driven by diffusion, but more of a ballistic transport.

Effects of hydrostatic pressure, temperature, and position-dependent mass on the nonlinear optical properties of triple delta-doped GaAs quantum well

In this study, we thoroughly investigate the impacts of hydrostatic pressure, temperature, and position-dependent mass (PDM) on the nonlinear optical properties of asymmetric triple δ-doped GaAs quantum wells. Our analysis covers total optical absorption coefficients, relative refractive index changes, nonlinear optical rectification, second harmonic generation, and third harmonic generation. Initially, we employ PDM to solve the time-independent Schrödinger equation using the diagonalization method under effective mass and parabolic band approaches, considering pressure and temperature dependencies. Utilizing the first four energy eigenvalues and eigenfunctions, we apply the compact density matrix method to compute the system’s nonlinear optical properties numerically. The results indicate a shift in optical property peak positions toward lower (higher) energy spectra with increasing hydrostatic pressure (temperature). Furthermore, the influence of PDM shifts the system’s optical properties toward the higher energy spectrum, resembling the effect of temperature. From an experimental and theoretical perspective, one of the topics that researchers work on most is GaAs-based δ-doped systems (δ-doped heterojunction bipolar transistors, δ-doped field effect transistors, δ-multiple independent gate field effect transistors, etc.). We believe these findings will provide valuable insights for the researchers involved in GaAs-based δ-doped optoelectronic device design.

Superconductivity investigation of (Bi,Pb)-2223 added with different nanoferrites and their composites

Abstract In this study, the impact of different types of nanoferrites additions of Zn0.5Ni0.5Fe2O4 and Ba0.4Sr0.4Ca0.2Fe12O19 nanoparticles and their nanocomposite of (Zn0.5Ni0.5Fe2O4)0.5 (Ba0.4Sr0.4Ca0.2Fe12O19)0.5 on the structural and normal state resistivity of Bi1.6Pb0.4Sr2Ca2Cu3O10, ((Bi,Pb)-2223) superconducting phase were systematically investigated. The samples were synthesised using high purity oxide powders via a solid-state reaction approach. Based on the Rietveld analysis of X-ray diffraction (XRD) data, the tetragonal structure of (Bi,Pb)-2223 was established to be the predominant phase for all composite samples of the three nano-additions' contents. However, a little change to the lattice parameters (a and c) was obtained. Furthermore, the small amounts (0.04 wt. %) of Ba0.4Sr0.4Ca0.2Fe12O19 and (Zn0.5Ni0.5Fe2O4)0.5(Ba0.4Sr0.4Ca0.2Fe12O19)0.5 improved the development of the (Bi,Pb)-2223 phase. The volume fraction of the (Bi,Pb)-2223 phase increased from 86.47 % to 88.73 % and 88.69 %, respectively. Then, it declined to 74.25 % and 71.48 % upon rising x to 0.40 wt. %, respectively, as well as for Zn0.5Ni0.5Fe2O4 nanoparticles up to 0.40 wt.%. SEM images verify the host superconducting matrix's granular structure for all three nanoadditions up to 0.40 wt.%. The existence of three nano additions in the host superconductor matrix is verified by employing energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analysis. The measurements for the resistivity dependency of temperature presented that, as compared to the pure sample (Tc = 108.67 K), the nano-(Zn0.5Ni0.5Fe2O4)xadded in the (Bi,Pb)-2223 phase exhibits more negative impact than it is with the other two additions.In contrast, the nano-(Ba0.4Sr0.4Ca0.2Fe12O19)x has the highest value of TC with a value of 110.95 K at x = 0.04 wt.%. Furthermore, the superconducting transition width (∆Tc) improved for all composite samples except for the sample at x = 0.04 wt.%, for Ba0.4Sr0.4Ca0.2Fe12O19 and (Zn0.5Ni0.5Fe2O4)0.5 (Ba0.4Sr0.4 Ca0.2Fe12O19)0.5 which showed the sharpest transition width. This suggests that their addition is anticipated to act as artificial pinning centers and strengthen the coupling between the grains in the (Bi,Pb)-2223 ceramic.&amp;#xD;

Electrical conductivity of stevia rebaudiana-surfactant mixture aqueous solution: Roles of temperature and sugar substitute concentration

The investigation of stevia-surfactant systems is of significant importance for the extraction process of steviol molecules as well as for the formulation of food products. The present study investigates the electrical conductivity of aqueous solutions containing a sugar substitute and surfactant over a temperature range of 25–50 °C. The sugar-substitute, Stevia Rebaudiana, concentration Cs (g/mL), is ranged from 0.047 to 0.6. The surfactant, Sodium bis(2-ethylhexyl) sulfosuccinate (AOT), has a concentration range of 1.4 ≤CAOT (g/L)≤ 6. The degree of ionization in ionic micelles, α, is determined by examining the conductivity of AOT in Stevia-free water, where complete micelle dissociation is observed. In the presence of Stevia Rebaudiana, a significant exponential decay in system conductivity with respect to the concentration of the sugar substitute is observed. Empirical equations were introduced to describe this behavior. The temperature dependence of conductivity is modeled using an Arrhenius equation. We postulate the formation of pseudo-micelles arising from interactions between the sugar substitute and surfactant, characterized by an effective degree of ionization in ionic micelles, αe.

Weak localization and magnetoresistance phenomena of hydrogen-annealed WO3 films

We explore the electronic transport properties of hydrogenated epitaxial WO3 films. Ionized hydrogen not only generates an electron carrier but also acts as an impurity center, providing a useful approach to investigate a macroscopic quantum transport phenomenon of weak localization. Temperature dependent-resistivity and anomalous magnetoresistance results are analyzed based on Mott's variable range hopping and weak localization. From the model studies, the phase coherence length is estimated to have a temperature dependence of T −1.6 and is determined to vary from ∼22 nm at 80 K to ∼180 nm at 20 K. The length at 20 K is of a similar order of magnitude of film thickness, which requires a dimensional crossover between three-dimensional and two-dimensional localization.

Studies on temperature dependent volume compression of nanomaterials with varying shape and size using suitable equation of state

Simple theoretical equation of state has been derived to study the dependency of size, shape and temperature of the nanostructures. Qi and Wang model of equation of state (EoS) is extended to study the size and shape dependent compression ratio for Se nanoparticle. The compression ratio (V/V0) increases with temperature across nanoparticles of various sizes. The computed data for volume compression ratio are compared with available experimental data and found in good agreement. A good agreement between theoretically calculated and experimental result proves the usefulness of the model to study the thermal properties of nanoparticles.

Invited Article: The oxidation kinetics and mechanisms observed during ultra-high temperature oxidation of (HfZrTiTaNb)C and (HfZrTiTaNb)B2

Ultra-high temperature ceramics (UHTCs), most notably transition metal carbides and borides, exhibit melting temperatures exceeding 3000 °C, making them appropriate candidates to withstand the extreme temperatures (∼2000 °C) expected to occur at the leading edges of hypersonic vehicles. However, their propensity to react rapidly with oxygen limits their sustained application. The high entropy paradigm enables the exploration of novel UHTC compositions that may improve on the oxidation resistance of conventional refractory mono-carbides and -diborides. The oxidation kinetics of candidate high entropy group IV + V (HfZrTiTaNb)C and (HfZrTiTaNb)B2 materials were evaluated at 1500–1800 °C using Joule heating in one atmosphere 0.1%–1% oxygen/argon gas mixtures for times up to 15 min. Possible mechanisms based on the resulting complex time, temperature, and oxygen partial pressure dependencies are discussed. The carbides formed porous and intergranular oxides. Oxidation resistance was improved upon a continuous external scale formation. The diborides formed dense external scales and exhibited better oxidation resistance compared to the carbides. This improvement was attributed to the formation of liquid boria. Both compositions showed an unexpected reduction in material consumption at 1800 °C for all times tested, compared to results at lower temperatures. An in-depth analysis of the composition and morphology of the oxide scale and sub-surface regions for specimens tested at 1800 °C revealed that the formation of denser group IV-rich (Hf, Zr, Ti) oxides mitigated the formation of the otherwise detrimental liquid-forming group V (Ta, Nb) oxides, leading to the improved oxidation resistance.

Temperature retrieval of near space with the combined use of O2(a1Δg) and O2(b1∑+ g) dayglow emissions under self-absorption effect correction

Atmospheric temperature information in the near space is of great academic significance and engineering value to support the development and utilization of the near space. Based on the theory of O2 molecular dayglow spectroscopy and the mechanism of atmospheric radiative transfer, a method is proposed for the joint retrieval of temperature profiles in the near space using O2(a1Δg) and O2(b1∑+g) bands dayglow spectroscopy signal with the self-absorption effect. First, the temperature dependence of O2(a1Δg) and O2(b1∑+g) bands dayglow is investigated, and the influence of the self-absorption effect on the radiative transfer characteristics is analyzed in the limb-view mode. Then, with the use of the onion peeling algorithm, the dayglow emission spectra signals of the O2(a1Δg) and O2(b1∑+g) bands measured by the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) in the limb-viewing mode were processed, and combined with optimization algorithms, the temperature profiles from 35 km to 120 km is successfully retrieved. Finally, the accuracy and reliability of the self-absorption effect correction as well as the joint temperature retrieval were verified by comparing with temperature product data from remote sensing satellites such as Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), Atmospheric Chemistry Experiment Fourier-Transform Spectrometer (ACE-FTS), and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The error analysis shows that the temperature retrieval error after correction for the self-absorption effect is about 3 K minimum and 20 K maximum.

Atmospheric chemistry of CF3CHFCF2OCH3 (HFE-356mec3) and CHF2CHFOCF3 (HFE-236ea1) initiated by OH and Cl and their contribution to global warming.

The kinetic study of the gas-phase reactions of hydroxyl (OH) radicals and chlorine (Cl) atoms with CF3CHFCF2OCH3 (HFE-356mec3) and CHF2CHFOCF3 (HFE-236ea1) was performed by the pulsed laser photolysis/laser-induced fluorescence technique and a relative method by using Fourier Transform infrared (FTIR) spectroscopy as detection technique. The temperature dependences of the OH-rate coefficients (kOH(T) in cm3s-1) between 263 and 353K are well described by the following expressions: 9.93 × 10-13exp{-(988 ± 35)/T}for HFE-356mec3 and 4.75 × 10-13exp{-(1285 ± 22)/T} for HFE-236ea1. Under NOx-free conditions, the rate coefficients kCl at 298K and 1013mbar (760Torr) of air were determined to be (2.30 ± 1.08) × 10-13 cm3s-1and (1.19 ± 0.10) × 10-15 cm3s-1, for HFE-356mec3 and HFE-236ea1, respectively. Additionally, the relative kinetic study of the Cl + CH2ClCHCl2 reaction was investigated at 298K, as it was used as a reference reaction in the kinetic study of the Cl-reaction with HFE-356mec3 and discrepant rate coefficients were found in the literature. The global atmospheric lifetimes were estimated relative to CH3CCl3 at the tropospheric mean temperature (272K) as 1.4 and 8.6years for HFE-356mec3 and HFE-236ea1, respectively. These values combined with the radiative efficiencies for HFE-356mec3 and HFE-236ea1 derived from the measured IR absorption cross sections(0.27 and 0.41 W m-2 ppv-1) yield global warming potentials at a 100-yrs time horizon of 143 and 1473, respectively. The contribution of HFE-356mec3 and HFE-236ea1 to global warming of the atmosphere would be large if they become widespread increasing their atmospheric concentration.

Ultralow Thermal Conductivity in Vacancy-Ordered Halide Perovskite Cs3Bi2Br9 with Strong Anharmonicity and Wave-Like Tunneling of Low-Energy Phonons.

Halide perovskites are of great interest due to their exceptional optical and optoelectronic properties. However, thermal conductivity of many halide perovskites remains unexplored. In this study, an ultralow lattice thermal conductivity κL (0.24W m-1 K-1 at 300 K) is reported and its weak temperature dependence (≈T-0.27) in an all-inorganic vacancy-ordered halide perovskite, Cs3Bi2Br9. The intrinsically ultralow κL can be attributed to the soft low-lying phonon modes with strong anharmonicity, which have been revealed by combining experimental heat capacity and Raman spectroscopy measurements, and first-principles calculations. It is shown that the highly anharmonic phonons originate from the Bi 6s2 lone pair expression with antibonding states of Bi 6s and Br 4p orbitals driven by the dynamic BiBr6 octahedral distortion. Theoretical calculations reveal that these low-energy phonons are mostly contributed by large Br motions induced dynamic distortion of BiBr6 octahedra and large Cs rattling motions, verified by the synchrotron X-ray pair distribution function analysis. In addition, the weak temperature dependence of κL can be traced to the wave-like tunneling of phonons, induced by the low-lying phonon modes. This work reveals the strong anharmonicity and wave-like tunneling of low-energy phonons for designing efficient vacancy-ordered halide perovskites with intrinsically low κL.