Low Temperature Region Research Articles

Reduced sulfur compound formation from a leachate-saturated zone under changing temperature conditions

In the leachate-saturation zone of landfills, sulfate reduction is influenced by temperature and electron donors. This study assessed sulfate reduction behaviors under varied electron donor conditions by establishing multiple temperature variation scenarios based on stable temperature fields within the leachate-saturation zone. The results showed that temperature variations altered the microbial community structure and significantly influenced the sulfate reduction process. A more pronounced effect was observed with a temperature difference of 30 °C compared to one of 10 °C. In addition, sulfate reduction was influenced by the presence of electron donors and acceptors. In the middle and low-temperature regions (35 °C and 25 °C), sulfate reduction reaction of acidic organic matter was more significant, while alcohol and saccharide organic substances were more effective in promoting sulfate reduction at high-temperature regions (55 °C). Notably, a 30 °C temperature difference within the leachate-saturation zone significantly altered the microbial community structure, which influenced the sulfate reduction behavior. In particular, Firmicutes and Synergistota played essential roles in mediating the variance in sulfate reduction efficiency with a 30 °C decrease and 30 °C increase, respectively. The results also revealed that temperature changes within landfills were influenced by leachate migration, therefore, controlling leachate recharge can help prevent secondary risks associated with sulfate reduction processes.

Hot deformation behavior and microstructural evolution of a new type of 7xxx Al alloy

Optimizing the thermal deformation parameters of Al alloys is beneficial for achieving grain refinement, avoiding microscopic defects in materials, and significantly enhancing the mechanical properties of Al alloys. In this study, the hot deformation behavior of a new type of 7xxx Al alloy was investigated through hot compression tests at strain rates of 10−3-1 s−1 and temperatures of 250–420 °C. The constitutive equation was successfully established using the hyperbolic sine form of the Arrhenius equation, accurately describing the flow stress. The hot processing map was obtained by overlaying the power dissipation map and the instability map, determining the optimal hot working parameters to be in the range of 325–373 °C, 0.45–1 s−1. In the safe region, dynamic recovery (DRV) and dynamic recrystallization (DRX) were predominant. The instability in the low-temperature region was attributed to the grain boundary pinning effect caused by grain boundary precipitation, while the instability in the high-temperature region was associated with local shear bands induced by uneven plastic strain. The hot processing map establishes a good connection with the microstructural evolution of the new type of 7xxx Al alloy under different hot deformation parameters.

The effect of Cu-doping to the DLC interlayer on the temperature dependent current-conduction mechanisms and barrier shape of the Schottky devices

The objective of this study is to determine the temperature and voltage-dependent current conduction mechanisms (CCMs) of the Al/Cu-doped DLC/p-Si Schottky device. It is aimed to obtain extensive and detailed data by current-voltage (I–V) measurements taken with 0.3 V voltage steps in the ±4 V voltage range, at 30 K intervals from 80 K to 410 K. Firstly, an examination of the semi-logarithmic I–V curve revealed that the low temperature (LTs, 80 K–170 K), medium temperature (MTs, 200 K–290 K) and high temperature (HTs, 320 K–410 K) regions should be examined separately. The basic parameters of the Schottky device such as the ideality factor (n), reverse saturation current (Io) and zero-biasing potential barrier height (ΦBo) were obtained separately for LTs, MTs and HTs by the Thermionic Emission (TE) theory. The results obtained show that the device deviates from ideality, especially in LTs and HTs, and the n values decrease with increasing temperature, while the ΦBo values increase. The analysis of the presence of other CTMs in the Schottky device revealed that Field Emission (FE) and Thermionic Field Emission (TFE) were effective in LTs and MTs, while FE was effective in HTs. Since it is thought that quantum mechanical CTMs cannot be the cause of such a deviation from ideality due to the interface layer thickness, the existence of Gaussian Distribution originating from lateral barrier inhomogeneity was investigated. As a result, it is concluded that the Multiple Gaussian Distribution (MGD) is dominant in the possible CTMs of the Schottky device.

Two-gap superconducting states of LaRu[formula omitted]Si[formula omitted]

We synthesize high-quality LaRu3Si2 (Tc= 7.5 K) polycrystalline sample and report the superconducting gap anisotropy relative to the temperature dependence of μ0Hc2 and Cel/γTc below Tc. The μ0Hc2 satisfies T-linear dependence until it approaches a low temperature region (T≤0.25Tc), and this behavior may not agree with the WHH theory. Based on T-linear fitting, the μ0Hc2(0) is estimated to be 10.2 T. The Cel/γTc below Tc cannot be expressed by a simple exponential fit. It is considered that although a larger gap (2Δ1/kBTc=3.63) opens at 3 K ≤T≤Tc, low-lying quasiparticle excitations at T≤ 3 K are dominated by a smaller gap (2Δ2/kBTc=2.62). Our experimental results indicate the feasibility of a two-gap superconducting state of LaRu3Si2.

Integrating Polyoxometalate into Dy(III)-based Single-molecule Magnets with Pentagonal Bipyramidal Symmetry.

Polyoxometalates (POMs) with various coordination fashions are versatile ligands for constructing single-ion magnets (SIMs), but enforcing POM-SIMs with a specific geometry remains a synthetic challenge. Herein, we synthesized a POM-cocrystallized DyIII-SIM [Dy(OPPh3)4(H2O)3][PW12O40]·4EtOH (1Dy) and a POM-ligated DyIII-SIM [{Dy(OPPh3)3(H2O)3}{PW12O40}]·Ph3PO·H2O (2Dy) with pentagonal bipyramidal local coordination geometry. Magnetic measurements indicate that 1Dy displays field-induced single-molecule magnet (SMM) behavior and the relaxation is dominated by under-barrier processes. 2Dy exhibits spin-lattice relaxation at a broader temperature region with a reversal barrier over 300 K. Magneto-structural analysis reveals that the enhancement of SMM behavior originated from the equatorial replacement of Ph3PO by POM, which strengthens the axial anisotropy in 2Dy. Luminescent experiments indicate that the characteristic DyIII emissions of 1Dy are covered up by the strong π-π* emission of Ph3PO at low-temperature regions. As for 2Dy, partial DyIII emission persists thanks to the antenna effect between DyIII and POM.

Hydrogen diffusion and hydrogen embrittlement in iron (steel)

This article examines the diffusion of hydrogen (H-diffusion) and the temperature dependences of the diffusion coefficient of hydrogen (DH) in the metal (M)-hydrogen system. The metal used was iron and low-alloy steel. Taking into account experimental data on hydrogen diffusion in the Fe-H and steel-H systems, the main diffusion parameters were calculated and compared. It is shown that the temperature dependences of the hydrogen diffusion coefficient in metal samples in a one-stage reaction under isothermal conditions are described by the Arrhenius equation. For some M-H systems, experimental data show a deviation of the diffusion coefficient from the ideal one calculated using the Arrhenius equation. This discrepancy can be eliminated using the statistical theory of absolute reaction rates. For the temperature range 25–1250 oС, the pre-exponential coefficient and activation energy of hydrogen diffusion in a body-centered cubic (bcc) lattice of iron (α–Fe) were calculated using the Arrhenius equation. These parameters make it possible to describe the dependence of the rate of hydrogen diffusion in a metal on temperature and to predict the behavior of hydrogen diffusion when changing the conditions of the kinetic process (concentration of substances, pressure, structure, composition, etc.). Tabular values of the calculated pre-exponential factor and activation energy of hydrogen diffusion in previously studied iron-based samples are presented. The temperature dependences of the hydrogen diffusion coefficient in a lattice of iron α–Fe can be divided into low-temperature and high-temperature regions. The calculated diffusion parameters of hydrogen in the metal lattice for the low-temperature 25– 800 oC and high-temperature 800–1250 oC regions differ markedly from each other. In addition, these calculated values are significantly influenced by the structure and composition of the metal. We also studied the diffusion of hydrogen in α-iron using ab initio density functional calculations. Molecular dynamics calculations using transition state theory were used. The calculated diffusion coefficient of hydrogen in α-Fe is consistent with previously obtained experimental data. Hydrogen embrittlement (HE) is considered using internal pressure, hydrogen enhanced localized plasticity (HELP) and hydrogen enhanced decohesion embrittlement (HEDE) theories.

Rotational holographic transport from Kerr-Newman-AdS black hole

We consider rotational holographic transport in strongly coupled 2+1-dimensional systems, from the point of view of 3+1-dimensional gravity. We consider the moment of inertia I as a kind of transport coefficient, identified with the moment of inertia of a charged rotating black hole in AdS4 background. In the low-temperature region, we find the behavior of the density I/A with temperature T and angular velocity Ω and find a quadratic behavior for ∂(I/A)/∂Ω with T, in the presence of some charge Q. Published by the American Physical Society 2024

NOx generation in marine dual-fuel engines: Effects of ammonia blending ratio and spark ignition timing

Ammonia application in marine engines can effectively mitigate greenhouse gas emissions. However, engines powered by ammonia produce considerably higher levels of NOx emissions compared to conventional fuel engines. In the present study, a combustion model for the marine dual-fuel engine fueled with natural gas and ammonia has been established using the CONVERGE software. The nitrogen element-tracking method is employed in the engine combustion simulation. This study aims to investigate the effects of ammonia blending ratio (XNH3 = 0% ∼ 50%) and spark ignition timing (SIT = −20 °CA ATDC ∼ −40 °CA ATDC) on the emission characteristics and spatiotemporal distribution of nitrogen-based pollutants under lean-burn and stoichiometric-burn conditions. The results indicate that as the XNH3 increases, total NOx emissions decrease at stoichiometric-burn conditions, while it initially increases and then decreases at lean-burn conditions, reaching a peak of 3760 ppm at XNH3 = 30%. Besides, fuel NO emissions are predominant at lean-burn conditions, whereas at stoichiometric-burn conditions, thermal N*O emissions are predominant. Additionally, as the SIT advances, total NOx emissions initially decrease and then remain unchanged, reaching a minimum at −35 °CA ATDC, and it gradually increases at lean-burn combustions. Furthermore, the spatial distribution of NO at CA50 illustrates that fuel NO is primarily concentrated at the flame front, while thermal N*O predominates in the high-temperature burned region. N2O is observed in the low-temperature region near the cylinder wall during the expansion stroke. Moreover, fuel NO is primarily produced by ammonia's decomposition with OH radicals. There are three dominant reactions for the formation of NO: HNO→NO, NH→NO, and N→NO. The coupling mechanism of carbon and nitrogen elements is achieved by H2CN and HCN radicals.

Development of an ammonia/diesel combustion mechanism for high ammonia energy ratio: Validation of the mechanisms in kinetic simulation and RCCI optical engine simulation

Ammonia blending in diesel is an efficient combustion strategy that overcomes the combustion resistance of ammonia while maintaining high engine adaptability. A smaller and accurate chemical kinetic mechanism is crucial for exploring the application of ammonia/diesel in engine. This study, based on the stepwise validation and optimization mechanisms, developed a novel ammonia/diesel mechanism comprising 130 species and 772 reactions. The mechanism was validated through kinetic verification for ammonia, n-dodecane, diesel and ammonia/diesel fuel. For profound understanding of the low-temperature autoignition chemistry of ammonia/diesel, applying this mechanism construct precise CFD models in RCCI optical engine. The results indicate that this mechanism can accurately capture ignition under high AER, wide working conditions, and low-temperature conditions. In the kinetic analysis, the C–N interaction reaction, particularly C2H4+NH2=C2H3+NH3, plays a crucial role in predicting the IDT of ammonia/diesel. In addition, NH2 undergoes deoxygenation reaction with HO2, converting inactive radicals HO2 into OH active radicals, enhances the reactivity of ammonia/diesel under low-temperature conditions. Applying the mechanism to CFD models, the model accurately predicts the pressure and heat release rate in RCCI optical engine, capturing the phenomenon of the high-temperature flame rapidly spreading towards the low-temperature regions in the cylinder. The research on this mechanism can construct accurate CFD model for optimizing efficient and clean combustion simulations of ammonia/diesel.

Structural, magnetic, optical and electronic properties of Gd2NiIrO6

Polycrystalline Gd2NiIrO6 double perovskite compound was synthesized by the solid-state route. Rietveld refinement of the X-ray diffraction pattern revealed that the compound was crystallized in a monoclinic structure with P21/n space group (IUCr. No. 14). The scanning electron micrograph showed that the grains were spherical and well distributed with an average grain size of around 1 μm. The temperature-dependent magnetic measurements showed magnetic transitions at 165 K and 149 K in the low-temperature region. Below the transition temperatures, weak ferromagnetism was evidenced by field-dependent magnetization measurements. Exchange bias effects were observed which were driven by Dzyaloshinsky–Moriya interactions in the compound. The UV–visible measurement evidenced that the compound had an optical band gap of 1.8 eV. The electronic structure calculations using the DFT + U method revealed that Gd2NiIrO6 compound exhibited a bandgap only when on-site correlations for the d-states were included, and the calculation showed that the AF1 configuration was energetically favourable.

A Monte Carlo study of Magnetic and thermodynamic behaviors of L[formula omitted] structure like quadrangular frustum pyramid nanoisland

Based on the Monte Carlo simulation, research has been conducted on the magnetic and thermodynamic behaviors of a ferrimagnetic mixed-spin (5/2, 1/2) L10 nanoisland with a like quadrangular frustum pyramid structure. We studied the effects of the magneto-crystal anisotropy and exchange coupling on the magnetization, susceptibility, internal energy, and hysteresis loops. The ferrimagnetic system exhibits more abundant magnetic and thermodynamic behavior than the cubic L10 nanoisland. We found eight saturation values of magnetization, five-loop hysteresis loops, and abrupt transitions in the low-temperature region. In addition, the exchange coupling effect of ferrimagnetism also promotes magnetic properties. Interestingly, in this system, the ferromagnetic exchange coupling (Jaa) and external magnetic field (h) linearly depend on the blocking temperature TB. The hysteresis loops of the system have more magnetization steps, which reflects that it has more ground state spin configurations.

Irreversibility in belief dynamics: Unraveling the link to cognitive effort.

The relationship between time irreversibility in neuronal dynamics and cognitive effort is a subject of growing interest in the scientific literature. Although correlations between proxies of both concepts have been experimentally observed, the underlying precise linkage between them remains elusive. Here we investigate the case of learning in decision-making tasks; we do so by introducing a thermodynamically grounded metric-inspired by Landauer's principle-which connects time-irreversible information processing to energy consumption. Equipped with this metric, we investigate the role of macroscopic time-reversal symmetry breaking in belief dynamics for the case of an agent with finite sensitivity while performing a static two-armed bandit task-a standard setup in cognitive neuroscience. To gain insights into the belief dynamics, we analogize it to the dynamics of an active particle subject to state-dependent noise and living in a two-dimensional space. This mapping allows an analytical description of learning-induced biases. We deeply explore the case of Q-learning with forgetting the nonchosen option. In this case, learning-induced risk aversion is formally equivalent to standard thermophoresis, i.e., the net motion towards low-temperature regions. Finally, we quantify the irreversibility of belief dynamics in the steady state for different bandit configurations, sensitivity levels, and exploitative behavior. We found a strong correlation in high-sensitivity learning between heightened irreversibility in belief dynamics and improved decision-making outcomes. Notably, as the task's difficulty increases, a greater degree of irreversibility in belief dynamics becomes necessary for having superior performances; this explicitly unravels a plausible connection between time irreversibility and cognitive effort. In conclusion, our investigation reveals that irreversibility in belief dynamics bridges out-of-equilibrium statistical physics concepts and cognitive neuroscience. In decision-making contexts, this perspective offers insights into the notion of cognitive effort, suggesting a potential mechanism driving the evolution of living systems toward out-of-equilibrium structures.

The Marginal Effect and LSTM Prediction Model under the Chinese Solar Greenhouse Film

The solar greenhouse is a significant agricultural facility in China. It enables the cultivation of crops during periods that do not coincide with the natural growing season, thus alleviating the pressure on the supply of fruits and vegetables during the winter months. The primary rationale behind the necessity of greenhouse cultivation lies in the fact that the temperature conditions conducive to optimal crop growth can be precisely replicated within this controlled environment. However, it is important to acknowledge that a distinct low-temperature area persists under the film during the overwintering period, with the precise delineation of its boundaries and distribution patterns remaining uncertain. In order to investigate the characteristics of the temperature distribution within the marginal region under the solar greenhouse film, experimental studies, CFD simulations, and LSTM prediction models were employed. The results of these studies indicate that, during the overwintering period, a low-temperature region was observed with approximately equal temperatures near the film membrane. The maximum horizontal distance from the south-side bottom corner was 6130 mm, while the minimum height from the ground was 600 mm. The lowest temperature in the low-temperature region was 4 °C, and the maximum observed temperature difference within the same period in different months was 1 °C. Additionally, a region of elevated temperatures was observed under the film. The lowest temperature in this region was 36.7 °C, and the highest temperature point was within the optimal range for crop growth. The CFD numerical simulation results were consistent with the actual observations, and the LSTM prediction model demonstrated high reliability. The findings of this study offer a theoretical foundation for the distribution of high and low temperatures in solar greenhouses. Furthermore, the developed prediction model provides the necessary buffer time for control, thus enhancing the efficiency of greenhouse cultivation.

Low-Temperature Methane Combustion Using Ozone over Coβ Catalyst.

Catalytic methane (CH4) combustion is a promising approach to reducing the release of unburned methane in exhaust gas. Here, we report Co-exchanged β zeolite (Coβ) as an efficient catalyst for CH4 combustion using O3. A series of ion-exchanged β zeolites (Co, Ni, Mn, Fe, and Pd) are subjected to the catalytic test, and Coβ exhibits a superior performance in a low-temperature region (<100 °C). The results of X-ray absorption spectroscopy (XAS) and catalytic tests for Coβ with different Co loadings indicate the isolated Co species is the plausible active site. The reaction mechanism of CH4 combustion over the isolated Co2+ cation is theoretically investigated by the single-component artificial force-induced reaction (SC-AFIR) method to thoroughly search for possible reaction routes. The resulting path toward CO2 formation shows an activation energy of 73 kJ/mol for the rate-determining step and an exothermicity of 1025 kJ/mol, which supports the experimental results. During a long-term catalytic test for 160 h without external heating, the CH4 conversion gradually decreases from 80 to 40%, but the conversion fully recovers after dehydration at 500 °C (0.5 h). The copresence of H2O and CO exhibits a negative impact on the catalytic activity, while NO and SO2 do not markedly change the catalytic activity.

Lithology and elevated temperature impact phoD-harboring bacteria on soil available P enhancing in subtropical forests

Plants are generally limited by soil phosphorus (P) deficiency in forest ecosystems. Soil available P is influenced by lithology, temperature, and soil microbes. However, the interactive effects of these factors on soil P availability in subtropical forests remain unclear. To assess their impacts, we measured soil inorganic and available P fractions and the diversity, composition, and co-occurrence network of phoD-harboring bacteria in two contrasting forest soils (lithosols in karst forests and ferralsols in non-karst forests) in the subtropical regions of southwestern China across six temperature gradients. The present results showed that the complexities in composition and network and the diversity indices of phoD-harboring bacteria were higher in the karst forest soils than those in the non-karst forest soils, with marked differences in composition. In both types of forest soils, the complexities of composition and networks and the diversity indices were higher in the high-temperature regions (mean annual temperature (MAT) > 16 °C) compared to the low-temperature regions (MAT <16 °C). Soil total inorganic and available P contents were lower in the karst forest soils compared to the non-karst forest soils. Soil total available P contents were lower in the high temperature regions than those in the low temperature regions in both forest soils, whereas soil total inorganic P contents were contrary. Variance partitioning analysis showed that soil inorganic and available P fractions were predominantly explained by lithology and its interaction with soil microbes and climate. The present findings demonstrate that soil P availability in subtropical forests of southwestern China is influenced by lithology and temperature, which regulate the diversity, composition, and network connectivity of phoD-harboring bacteria. Furthermore, this study highlights the significance of controlling the composition of phoD-harboring bacteria for mitigating plant P deficiency in karst ecosystems.

A high sensitivity temperature coefficient of the Au/n-Si with (CdTe-PVA) structure based on capacitance/conductance-voltage (C/G-V) measurements in a wide range of temperature

This study focused on revealing the temperature-sensing performance and rudimental electrical-properties of the Au/(CdTe-PVA)/n-Si depending on the temperature via impedance-measurements. The temperature-sensitivity (S) for constant-capacitance drive mode shows two-distinct linear-regions corresponding to low/moderate temperatures. The highest S value was achieved as 15.5 mV/K at 0.60 nF value. Nicollian-Brews and Hill-Coleman methods were applied to determine series-resistance (RS) and density of surface-states (NSS) values. The low RS values and the proper magnitude of NSS demonstrate the high quality and performance of the Au/(CdTe-PVA)/n-Si. Additionally, the electrical parameters obtained from C-2-V plots show almost temperature-independent behavior at moderate temperature regions. The low activation-energy values (Ea) determined via Arrhenius-plot indicate hopping of the trapped electron from trap to trap or conduction band dominates the ac conduction. In conclusion, the variations of electrical-parameters and the high S value consolidate the usability of Au/(CdTe-PVA)/n-Si as a thermal sensor in the low-temperature regions.

IMPROVING THE ACCURACY OF CALCULATING THE SUPER-COMPRESSIBILITY COEFFICIENT OF HELIUM BASED ON STATE EQUATIONS

To date, the Russian gas industry is developing a large number of deposits with a high helium content in the composition of the extracted gas, such as Chayandinskoye, Kovyktinskoye, Yaraktinskoye oil and gas condensate fields. Helium has never before been the object of detailed study during gathering and treatment, but today helium is an important resource that is used in many fields: military industry, medicine, shipbuilding, laser technology, space technology. The high demand for the component of the extracted gas has created requirements for the creation of a technology for separating it from gas. In addition, helium is a «cold» gas due to the weak interaction of its molecules, so it is difficult to model phase equilibrium at extremely low temperatures. As a result, improving the simulation of condensation of a helium mixture is undoubtedly an urgent task of the industry today. The purpose of the study is to increase the accuracy of calculating the thermodynamic properties of helium based on one of the modifications of the Peng-Robinson equation of state for thermobaric conditions corresponding to helium liquefaction processes.As the methods used in this work, a software module for calculating the selection of the Peneloux correction in the Java programming language was implemented. The results are tested on known experimental data, as well as a specialized software product for calculating the thermodynamic properties of fluids.The features of calculating the superconductivity coefficient of helium based on the cubic equation of state are presented. The optimal range of the Peneloux correction for the Peng-Robinson equation of state has been found, as well as an approximation formula that allows us to find the correction in the low temperature region. The results obtained will allow us to calculate the thermodynamic properties of helium with high accuracy. This will allow us to predict the volume of production and condensation of helium from natural gas, which is certainly an important task for the development of the country's economy.

Cover Image, Volume 62, Issue 13

The cover image is based on the Research Article Synthesis and chiroptical properties of β‐1,2‐linked glycopolymers prepared by click polymerization by Misaki Suzuki et al., https://doi.org/10.1002/pol.20230746In the cover image, Yasuhito Koyama and coworkers show the design, synthesis, and folding behaviors of β‐1,2‐linked glycopolymers as a bioconjugate‐based foldamer. The glycopolymers are synthesized via the click polymerization of alkyne‐containing β‐glycosyl azides. The galactose‐based polymer adopts a helically folded structure in ClCH2CH2Cl or THF. It is indicated that the glucose‐based polymer can possibly form the helical folded structure in ClCH2CH2Cl at a low temperature region and adopt a random coil structure at 50 °C. In THF, the glucose‐based polymer does not fold the conformation at all in the observed temperature region. image

Electrical conductivity of copper in the low temperature region of warm dense matter

In this study, electrical conductivity of copper in the low temperature part of a warm dense matter regime is investigated utilizing underwater electrical wire explosion. Specifically, for the vapor/plasma region with a density of ∼0.01 normal density, temperature up to 10 kK, and the liquid–vapor two-phase region below the binodal curve, the electrical conductivity of copper is measured as a function of density and temperature by means of shadowgraph imaging, spectroscopy, and electrical measurements. In this region, anomalous temperature dependence and characteristics originated from a phase transition are found. Based on the careful analysis of experiments and model calculations, it is revealed that bound electrons, in addition to free electrons, contribute significantly to the electrical conductivity in the vapor/plasma region, and that the associated phase transition kinetics play a substantial role in adequately describing the behavior in the liquid–vapor two-phase region. An improved electrical conductivity model emerging from our combined experimental and theoretical study that accounts for the characteristics in the low temperature regime of the warm dense matter is presented.

The comparative study of structural, optoelectronic and thermoelectric properties of Li-based half-Heusler alloys via GGA and meta-GGA functionals

The present work aims to investigate the effects of meta-GGA functionals on the structural, optoelectronic and thermoelectric properties of LiXY(X=Be, Mg, Zn, Cd and Y=N, P, As, Sb, Bi) half-Heusler alloys using density functional theory (DFT) and classical Boltzmann transport theory. The obtained lattice constants of these alloys are in good agreement with the experimental values, exhibiting a slight decrease slightly with meta-GGA functionals compared with GGA-PBE. Band structure calculations demonstrate that the materials exhibit semiconductor character and provide validation for the use of meta-GGA functionals, particularly the r2SCAN and rSCAN, to predict the band gap values of LiXY more accurately. Optical and thermoelectric properties are calculated and discussed in detail. The results reveal that the meta-GGA functionals predict a significant change compared with GGA-PBE in the low energy and temperature region, while in the high energy and temperature regions, all four functionals present almost the same change trends.