Cohesive Energy Research Articles

Diffusion quantum Monte Carlo study on magnesium clusters as large as nanoparticles

Nanoscale magnesium clusters are important potential hydrogen storage materials, and density functional theory (DFT) is mainly used for their theoretical investigation. The results of the coupled-cluster theory at the singles and doubles level with a perturbative treatment of triples [CCSD(T)] were employed previously to choose proper exchange–correlation (XC) functionals in DFT calculations for magnesium clusters, but it is too expensive to be applied to Mgn with n > 7. The diffusion Monte Carlo (DMC) method is employed in this work to study magnesium clusters up to nanosize. The error of atomization energies with DMC using single-determinant-Jastrow (SDJ) trial wavefunctions has been shown to be somewhat larger than that of CCSD(T) for many molecules. However, cohesive energies with DMC using SDJ for Mgn with n ≤ 7 are in excellent agreement with those of CCSD(T) using the aug-cc-pVQZ basis set, with a difference of less than 1 kcal/mol. DMC results are employed to investigate the performance of different XC functionals on magnesium clusters. Our results indicate that the PBE0 functional is the best XC functional for determining the lowest-energy isomer when compared with DMC results, while the RPBE functional is the best XC functional for calculating cohesive energies per atom of these magnesium clusters with a mean absolute error of 0.5 kcal/mol. These XC functionals are expected to provide reasonable results for even larger magnesium clusters.

Research on the Adhesion Properties of Fast-Melting SBS-Modified Asphalt-Aggregate Based on Surface Free Energy Theory.

In order to study the adhesion properties of fast-melting SBS-modified asphalt (SBS-T) at the interface with aggregates, the contact angles of three dosages of SBS-T asphalt with three liquids (distilled water, glycerol, and formamide) were determined by the sessile drop method based on surface free energy theory. The evaluation indexes such as cohesion, asphalt-aggregate adhesion, stripping work and energy ratio of the asphalt were analyzed and the adhesion properties of the asphalt-aggregate system were investigated with the help of micromechanical methods. The results indicate that SBS-T can improve the adhesion properties of the asphalt. Furthermore, as the dosage of the modifier increases, the cohesion work, adhesion work, and energy ratio of the SBS-T asphalt exhibit a similar rise. As the spalling work reduces and the adhesion between asphalt and aggregate improves, it is noteworthy that the SBS-T asphalt-aggregate system exhibits superior adhesion performance compared to the SBS-modified asphalt-aggregate system, despite the same dosage.

Empirical Model of Solvophobic Interactions in Organic Solvents

AbstractAn empirical model was developed to predict organic solvophobic effects using N‐phenylimide molecular balances functionalized with non‐polar alkyl groups. Solution studies and X‐ray crystallography confirmed intramolecular alkyl‐alkyl interactions in their folded conformers. The structural modularity of the balances allowed systematic variation of alkyl group lengths. Control balances were instrumental in isolating weak organic solvophobic effects by eliminating framework solvent‐solute effects. A 19F NMR label enabled analysis across 46 deuterated and non‐deuterated solvent systems. Linear correlations were observed between organic solvophobic effects and solvent cohesive energy density (ced) as well as changes in solvent‐accessible surface areas (SASA). Using these empirical relationships, a model was constructed to predict organic solvophobic interaction energy per unit area for any organic solvent with known ced values. The predicted interaction energies aligned with recent organic solvophobic measurements and literature values for the hydrophobic effect on non‐polar surfaces confirmed the model‘s accuracy and utility.

Empirical Model of Solvophobic Interactions in Organic Solvents.

An empirical model was developed to predict organic solvophobic effects using N-phenylimide molecular balances functionalized with non-polar alkyl groups. Solution studies and X-ray crystallography confirmed intramolecular alkyl-alkyl interactions in their folded conformers. The structural modularity of the balances allowed systematic variation of alkyl group lengths. Control balances were instrumental in isolating weak organic solvophobic effects by eliminating framework solvent-solute effects. A 19 F NMR label enabled analysis across 46 deuterated and non-deuterated solvent systems. Linear correlations were observed between organic solvophobic effects and solvent cohesive energy density (ced) as well as changes in solvent-accessible surface areas (SASA). Using these empirical relationships, a model was constructed to predict organic solvophobic interaction energy per unit area for any organic solvent with known ced values. The predicted interaction energies aligned with recent organic solvophobic measurements and literature values for the hydrophobic effect on non-polar surfaces confirmed the model's accuracy and utility.

Data-driven discovery of ultraincompressible crystals from a universal correlation between bulk modulus and volumetric cohesive energy

Bulk modulus and cohesive energy are two important quantities of condensed matter. From the interatomic energy landscape, we here derived a correlation between the bulk modulus (B) and the volumetric cohesive energy (ρ e), i.e. B = 2(ln2)2 ρ e/9ϵ s 2 = kρ e, where ϵ s and k are the strain-to-failure of interatomic bonds and the factor of proportionality, respectively. By analyzing numerous crystals from first principles calculations, it was shown that this correlation is universally applicable to various crystals including simple substances and compounds. Most interestingly, it was found that ϵ s of crystals with a similar structure are almost a constant, resulting in a linear relationship between B and ρ e. Furthermore, we found that the value of k for any compound can be determined based on the rule of mixtures, i.e. k= ∑x i k i, where x i and k i are the atomic fraction and the factor of proportionality for each element in this compound, respectively. Finally, this correlation was used to predict the bulk moduli for a vast number of crystals with known ρ e in databases. After first principles verification of the top 50 crystals with the highest predicted bulk modulus, 25 ultraincompressible crystals with a bulk modulus greater than 400 GPa that can rival diamond (436 GPa) were discovered.

Enhancement in the optoelectronic and thermoelectric properties of the NaASb (A= Ca, Sr and Ba) Sodium Antimonides via switching from P4/nmm to P62 m symmetry

Structural, opto-electronic and thermoelectric properties of square and butterfly like structured NaASb (A = Ca, Sr and Ba) Sodium Antimonides in tetragonal and hexagonal symmetries (P4/nmm and P62 m) are investigated using of density functional theory (DFT). Structural properties are in good agreement with the reported outcomes. Cohesive energy per atom (−8.233 to −26.1004 for P4/nmm and −8.522 to −28.7306 for P62 m symmetry) and enthalpy of formation per atom (−0.9468 to −2.6800 for P4/nmm and −1.1721 to −2.8034 for P62 m symmetry) for these compounds reveals that these compounds are stable in both P4/nmm and P62 m symmetries and are more stable in P62 m space group as compare to P4/nmm symmetry. Electronic properties show that the transition from indirect to direct band gap nature occurs by replacement of Ca/Sr by Ba in P4/nmm symmetry while P62 m symmetry all the NaASb (A = Ca, Sr and Ba) compounds are direct bandgap semiconductors. The band gap values lie in the range of 0–1.393 in P4/nmm symmetry and 0.542 to 1.547, respectively, in P62 m symmetry. Electrical conductivity also reveals the semiconducting characteristics of these compounds. The study shows that the replacement of Ca by Sr and Ba reduces the band gap and the reduction in bandgap values is greater in P4/nmm symmetry as compared to P62 m. The outcome demonstrates that these compounds NaASb (A = Ca, Sr and Ba) are implicitly active optically in the infrared region and are capable of serving as the primary applicant for optoelectronic devices. Thermoelectric properties like Seebeck coefficient (−138.5 to 154.7 μV/K in P4/nmm, −36.5 to −125.3 μV/K in P62 m at 500 K), Power factor (1.33–3.05 GW/mK2s in P4/nmm, 0.152–0.322 GW/mK2s in P62 m at 500 K) and thermoelectric figure of merit ranges from 0.495 to 0.946 in P4/nmm and 0.016 to 0.260 in P62 m at 500 K shows that these compounds are potential candidates for thermoelectric application in P4/nmm symmetry.

First‐Principles Study of the Effects of C/N/S Doping on the Magnetic and Photocatalytic Properties of a Bilayer Anatase TiO2 (001)

Most studies have theoretically and experimentally investigated the effects of single‐element C/N/S doping on the magnetic and photocatalytic properties of three‐dimensional TiO2. However, only a few comparative studies are available on the magnetic and photocatalytic properties of two‐dimensional anatase TiO2 doped with C, N, or S. Based on the density functional theory framework, generalized gradient approximation + U method of the first principles is used to investigate the effects of doping three nonmetallic elements (C/N/S) on the magnetic and photocatalytic properties of bilayer anatase TiO2. The bilayer Ti24O47N (001) is found to have the lowest formation energy, the largest cohesion energy, is relatively stable, and exhibits magnetic property with a magnetic moment of −1.0 . The holes and electrons of Ti24O47N (001) system have longest carrier lifetime. The ratio of their average effective masses is 1.28, and the carrier separation in this system is good. The system is most favorable for the preparation of H2 and O2 from water decomposition. Within the 420–790 nm wavelength range, the Ti24O47N (001) system shows the strongest absorption spectrum intensity, the most prominent redshift, and the best activity. Thus, the bilayer Ti24O47N (001) system is an optimal photocatalyst.

Influence of the substitution of different functional groups on the gas sensing and light harvesting efficiency of zero-dimensional coronene quantum dot: A first principle DFT study

The present study accounts for the structural and electronic properties of a zero-dimensional coronene quantum dot (QD) and its substituted structures with seven different functional groups. The substitution of functional groups lead to the alteration of the centrosymmetric geometry of the coronene flake and thus, incredible properties were observed for the functionalized QDs. The increment in the band gap after the substitution of the functional groups was responsible for the increase in the chemical stability. The cohesive energy however decreased for the functional QDs. Fourier transform Infrared spectra were traced for all the QDs to confirm the availability of the functional groups and their participation in the chemical reactivity. After the substitution of functional groups, the extremely enhanced light harvesting efficiency of functionalized QDs was obtained. Furthermore, the sensing capability of the functionalized QDs for CO, CO2, and NH3 was also calculated and it was found that C-cyano, C-nitro, C-nitroso, C-pyrrolidine, and C-thionyl QDs have better sensing capabilities for CO2 molecules. C-pyrrolidine had the highest value of light harvesting efficiency of about 96%. This reflects the potential photosensitive candidature of C-pyrrolidine. Therefore, the present study sets a perfect benchmark for designing and fabricating efficient photosensitive materials and gas-sensing devices using the introduced QDs in the near future.

The extracellular polysaccharide determine the physico-chemical surface properties of Microcystis.

Microcystis possesses the capacity to form colonies and blooms in lakes and reservoirs worldwide, causing significant ecological challenges in aquatic ecosystems. However, little is known about the determining factors of physico-chemical surface properties that govern the competitive advantage of Microcystis. Here, The physico-chemical surface properties of Microcystis wesenbergii and Microcystis aeruginosa, including specific surface area (SSA), hydrophobicity, zeta potential, and functional groups were investigated. Additionally, the extracellular polysaccharide (EPS) were analyzed. Laboratory-cultured Microcystis exhibited hydrophilic, a negative zeta potential and negatively charged. Furthermore, no significant relationship was shown between these properties and the cultivation stage. Microcystis wesenbergii exhibited low free energy of cohesion, high surface free energy, high growth rate, and high EPS content during the logarithmic phase. On the other hand, M. aeruginosa displayed lower free energy of cohesion, high surface free energy, high EPS content, and high growth rate during the stationary phase. These characteristics contribute to their respective competitive advantage. Furthermore, the relationship between EPS and surface properties was investigated. The polysaccharide component of EPS primarily influenced the SSA and total surface energy of Microcystis. Likewise, the protein component of EPS influenced hydrophobicity and surface tension. The polysaccharide composition, including glucuronic acid, xylose, and fructose, mainly influenced surface properties. Additionally, hydrophilic groups such as O-H and P-O-P played a crucial role in determining hydrophobicity in Microcystis. This study elucidates that EPS influenced the SSA, hydrophobicity, and surface free energy of Microcystis cells, which in turn impact the formation of Microcystis blooms and the collection.

Ultraviolet enhanced inorganic graphenylene-like ZnMgX2 (X=O, S) for sensitive and reversible detection of toxic formaldehyde at room temperature: A first-principles study

This study investigates the interaction between formaldehyde (HCHO) and newly predicted graphenylene-like ZnMgX2 (X=O, S) monolayers based on first-principles calculations. It was found that the adsorption performance of HCHO molecule on pure ZnMgX2 monolayers was favorable and exothermic in nature, exhibiting no need for the presence of a metal support. Their experimental feasibility was proven through various analyses, including the evaluation of cohesive energy, phonon dispersion and ab initio molecular dynamics (AIMD) simulations. The results of the topological analysis indicate that the examined monolayers are stabilized by the mixed ionic-covalent bond. By systematically analyzing the adsorption energy, charge transfer, band gap, work function and presence of competing gases (H2O, N2, O2 and H2), their detection sensitivity and response times were determined. Under the presence of ultraviolet (UV) irradiation, the ZnMgO2 system demonstrates suitability as an electronic sensor for HCHO detection at room temperature, while ZnMgS2 with its large adsorption energy has the potential to be used for scavenging HCHO. Further investigation into the adsorption of H2O and O2 yields supporting evidence for high selectivity and improved recovery time of HCHO and potential formation of hydroxyl (•OH) and superoxide (O2•−) radicals, thereby establishing favorable conditions for eventual catalytic degradation of HCHO. This study will serve as a theoretical foundation for the development of HCHO gas sensors intended for both small-scale and industrial applications.

Two-dimensional MSi2N4 (M = Ge, Sn, and Pb) monolayers: promising new materials for optoelectronic applications

The recent growth of two-dimensional (2D) layered crystals of MoSi2N4 and WSi2N4 has sparked significant interest due to their outstanding properties and potential applications. This development has paved the way for a new and large family of 2D materials with a general formula of MA 2 Z 4. In this regard, motivated by this exciting family, we propose two structural phases (1T- and 1H-) of MSi2N4 (M = Ge, Sn, and Pb) monolayers and investigate their structural, vibrational, mechanical, electronic and optical properties by using first-principles methods. The two phases have similar cohesive energies, while the 1T structures are found to be more energetically favorable than their 1H counterparts. The analysis of phonon spectra and ab initio molecular dynamics simulations indicate that all the suggested monolayers, except for 1H-GeSi2N4, are dynamically and thermally stable even at elevated temperatures. The elastic stability and mechanical properties of the proposed crystals are examined by calculating their elastic constants (C ij ), in-plane stiffness (), Poisson’s ratio (ν), and ultimate tensile strain (UTS). Remarkably, the considered systems exhibit prominent mechanical features such as substantial in-plane stiffness and high UTS. The calculated electronic band structures reveal that both the 1T- and 1H-MSi2N4 nanosheets are wide-band-gap semiconductors and their energy band gaps span from visible to ultraviolet region of the optical spectrum, suitable for high-performance nanoelectronic device applications. Lastly, the analysis of optical properties shows that the designed systems have isotropic optical spectra, and depending on the type of the system, robust absorption of ultraviolet and visible light (particularly in 1H-PbSi2N4 monolayer) is predicted. Our study not only introduces new members to the family of 2D MA 2 Z 4 crystals but also unveils their intriguing physical properties and suggests them as promising candidates for diverse nanomechanical and optoelectronic applications.

Physical properties of W2GaX (X=C, N, and F) based novel MAX phases; potential materials for applications in advanced electronic and optical devices

This study examines the electronic and optical characteristics of W2GaX (X = C, N, and F) MAX phases using first-principles approach. The cohesive energies of W2GaC, W2GaN, and W2GaF are determined as 7.31, 6.40, and 5.05 eV, respectively, demonstrating excellent agreement with existing literature and confirming their stability. The W-d, Ga-s, and X-p states are symmetrically dispersed across the spin-polarized electronic structures, resulting in a nonmagnetic metallic behavior of W2GaX. Due to their metallic behavior, they reflect more than 60 % of infrared and up to 50 % of visible light. These compounds demonstrate considerable absorption of infrared, visible, and ultraviolet (UV) light, with absorption coefficients of approximately ∼104 cm−1, ∼105 cm−1, and ∼106 cm−1, respectively. The refractive indices of W2GaX MAX phases remain greater than one for incident light energies below 10 eV. Additionally, W2GaC shows the highest optical conductivity among the investigated compounds when exposed to light, making it a promising material for various conduction applications. Our present study sheds light on the optical and electronic properties of W2GaX MAX phases and highlights their potential for applications in advanced electronic and optical devices.

Study on inherent characteristics of asphalt regenerating agents: Insights from density functional theory calculations and molecular dynamics simulations

The asphalt mixtures containing reclaimed asphalt pavement (RAP) are gradually used in pavement. When the RAP content exceeds 25%, the influence of RAP properties on the performance of the asphalt mixture becomes more pronounced. To address this barrier, the incorporation of regenerating agents is adopted to soften RAP asphalt and ensure the performance of the asphalt mixture. Currently, research on the effect of regenerating agents is rapidly advancing, but there remains limited exploration of their inherent characteristics. This study employs advanced tools such as molecular dynamics (MD) simulations and density functional theory (DFT) to investigate the chemical properties and material attributes of regenerating agents. Fourteen common regenerating agents are selected, which can be classified into eight categories (A∼H) based on their structural features. The results reveal that linear alkanes and cycloalkanes are nonpolar surfaces due to their inherent structural characteristics, resulting in larger fraction free volume (FFV) values within the molecular structure. Considering the molecular weight and intermolecular interactions, these components exhibit a higher diffusion coefficient (D) value. In contrast, aromatics with benzene rings experience enhanced polarity and intermolecular interaction due to conjugated electron pairs forming π-π interactions, leading to reduced FFV values and D values. Moreover, the increase in molecular weight of aromatics significantly reduces both intermolecular interactions and D values. The carboxyl group in fatty acids leads to higher polarity, resulting in stronger intermolecular interactions and lower FFV values and D values. However, after esterification, the properties of fatty acid esters show improvement. Glycerol, with its hydroxyl group having the strongest polarity, exhibits a dense arrangement with the highest density and solubility parameters, which may exceed that of asphalt and may not be suitable as a rejuvenator. The investigation reveals that the polarity of regenerating agents is positively correlated with density, cohesive energy density, and solubility parameters.

Ab-initio insights into the structural, elastic, bonding, and thermophysical properties of UHx (x = 1, 2, 3, 5, 6, 7, 8) under pressure: Possible relevance to high-Tc superconductivity

Binary uranium hydrides, UHx (x = 1, 2, 3, 5, 6, 7, 8), with different crystal symmetries are potentially interesting compounds for high-Tc superconductivity and as hydrogen storage systems. In this work we have explored the structural, elastic, mechanical, bonding, and thermophysical properties of these systems under uniform pressure via density functional theory based computations. Most of the results disclosed in this work are novel. From the calculations of the cohesive energy and enthalpy of formation, we have found that the titled compounds are thermodynamically stable. The computed elastic constants at different pressures ensure elastic stability. All the binary hydrides are mechanically anisotropic. Pressure induced brittle-ductile transition takes place under high pressure. The compounds are machinable with the cubic α-UH3-Pm-3n showing very high value of the machinability index. All the compounds are fairly hard with cubic UH8 showing superhard character. The Debye temperatures and acoustic velocities of these compounds are high; the highest value is found for the cubic UH8. This is highly relevant to the predicted high-Tc superconductivity in cubic UH8 under hydrostatic pressure. The melting temperature, Grüneisen parameter, minimal phonon thermal conductivity, and the thermal expansion coefficient of these compounds have also been studied at different pressures. All these parameters show excellent correspondence with the estimated Debye temperature, elastic parameters and bonding characteristics.

Two-dimensional γ-PC3: A novel direct band gap semiconductor with ultrahigh carrier mobility for photovoltaics

Here, we report a novel two-dimensional phosphorus carbide, named γ-PC3, and determine its structural, electronic, transport, and photovoltaic characteristics utilizing density functional theory. γ-PC3 consists of P atom linked benzenes and has an anisotropic orthorhombic crystal structure. It exhibits excellent stability, as confirmed by the cohesive energy (6.38 eV/atom), phonon dispersion (the ultimate strain is as high as 13 %), molecular dynamics simulation, elastic modulus, and strain–stress relationship. The γ-PC3 monolayer has direct band gap (1.13 eV), ultrahigh electron mobility (up to 7.25 × 104 cm2 V−1 s−1 along armchair direction), and high optical absorption coefficient (up to 105 cm−1). By changing the stacking sequence and thickness to multilayer geometries or applying the tensile uniaxial strain to the monolayer geometry, its direct band gap and optical absorption coefficient can be effectively tuned. The γ-PC3/MoS2 heterojunction has a photoelectric conversion efficiency of 15.54 %, which demonstrates that γ-PC3 is a promising semiconductor for photovoltaics.

Exploring novel Zr2GeX (X = C, N, F) MAX phases by first-principles approach

In recent years, there has been a surge of interest in the thermodynamically stable nanolaminate ternary carbides/nitrides known as MAX phases. In this first-principles research work, we focus on the MAX phases with a particular emphasis on Zr2GeX (X = C, N, F) compounds. These novel Zr2GeX compounds exhibited considerable values of cohesive energy, demonstrating stability comparable to well-established MAX compounds. Our calculations for the structural parameters of Zr2GeX agree well with the literature, indicating the reliability of our results. The absorption coefficients for ultraviolet (UV) light are approximately 105/cm and 106/cm, respectively, highlighting their significance for energy harvesting devices. Additionally, these metallic compounds demonstrate impressive reflectivity, reflecting over 50% of infrared and visible light. Similarly, they exhibit the highest refraction for infrared light, with a significant decrease in refraction for visible and UV light. Consequently, the transparency of Zr2GeX compounds diminishes, rendering them opaque against UV light and highly likely to absorb most incident UV radiation. Results presented in this paper highlight the potential applications of Zr2GeX MAX phases for optoelectronic devices due to their exceptional electronic and optical properties.

Theoretical investigation of electronic, energetic, and mechanical properties of polyvinyl alcohol/cellulose composite hydrogel electrolyte

Hydrogels are a new class of electrolytic materials employed in zinc-air batteries due to their significant on the battery's performance. However, the effectiveness of electrolytic hydrogel is affected by factors such as water content, temperature, additives, etc. Using DMol3 and molecular dynamics modeling techniques, this research aimed at investigating the electronic properties, effect of water content, and temperature on the binding energy, cohesive energy, and the mechanical properties of polyvinyl alcohol/cellulose-based composite hydrogel at the molecular level. The electronic optimized structures of the polymeric materials and parameters such as frontier molecular orbitals, band gap and electron density were analyzed. The results revealed that the binding energies of hydrogel polymer composite increased as the number of water molecules in the composite increased up to 60 % after which the binding energy decreased. In addition, the temperature increase led to a decrease in the binding energy of the composite. The cohesive energy density of the composite was highest at 40 % water content while higher temperatures decreased the cohesive energy density of the hydrogel. As the number of water molecules increased from 29 to 256, the tensile modulus increased from 0.707 × 10−3 to 2.821 × 10−3 Gpa; while the bulk modulus (K) increased in the order of K 40 > 50 > 30 > 20 > 10 respectively. These results serve as a theoretical enlightenment and a guide for experimental works in the field of energy conversion and storage devices.

Unveiling the electronic structure and optical properties of two-dimensional TMDCs: first-principles study

Transition metal dichalcogenide (TMDC) materials are considered extremely efficient materials with significant applications in photovoltaics and optoelectronics. Here, the electronic structure and optoelectronic features of new transition metal-containing dichalcogenides are studied using state-of-the-art density functional theoretical calculations. For the analysis of the electronic band structures, we employed a modified Becke-Johnson potential. According to the band structure analysis, Platinum-based dichalcogenides possess an indirect band profile, having the valence band maximum and the conduction band minimum situated at discrete symmetry regions. At the same time, the zirconium-based materials have a direct type band structure at the same Γ-point. We calculated cohesive energies and formation energies to assess the stability of these materials. The substantial optical parameters such as the two parts of the dielectric constant, absorption coefficients, energy loss functions, reflectivity spectra, refractive index, real optical conductivity spectra, spectra, and the extinction coefficients, are calculated. These findings provide insight into potential applications in optoelectronic devices. The calculated band gaps and refractive index revealed an inverse relationship. This research aims to make a significant contribution to the advancement of various and possibly gainful semiconducting technologies, as well as their practical applications.

Optoelectronic and thermoelectric properties of spinel chalcogenides HgLa2X4 (X=S and Se): A first-principles study

We investigated spinel chalcogenides HgLa2(S/Se)4 by using density function theory, and scrutinized the structural, optical, electrical, mechanical and thermoelectric transport characteristics of HgLa2(S/Se)4 spinel chalcogenides. The enthalpy of formation, energy of cohesion, and energy volume optimum plots were used to obtain the stability as well as the perfect ground state of these materials. The ductility of these materials was the best illustrated with the help of Poisson's and Pugh's ratios. The band gap results were obtained using Trans and Blaha modified Becke-Johanson potential (TB-mBJ). Both the materials present semi-conducting nature with direct band gap equal to 1.449 and 0.892 eV respectively for HgLa2S4 and HgLa2Se4. Calculations were also made for optical characteristics with the values of dielectric function, absorption coefficient, optical conductivity, reflectivity, and refractive indices. According to the findings, both of these materials are suitable for infrared optoelectronic applications. These materials were found to have promising optoelectronic and thermoelectric applications after their optical properties and transport aspects were evaluated. Despite tiny levels of temperature conductivities, substantial amounts of power conductivities, the figure of merit (more than unity), as well as Seebeck coefficients all point to the potential use of both the materials in thermoelectric power generators.

Strong Thermo-tolerant Silicone-Modified Waterborne Polyurethane/Polyimide Pressure-Sensitive Adhesive.

A waterborne polyurethane pressure-sensitive adhesive (WPUPSA) has the advantages of low pollution and good viscoelasticity. However, its poor thermo-tolerance limits its application in the field of high temperatures. Hence, a novel silicone-modified strong thermo-tolerant waterborne polyurethane/polyimide pressure-sensitive adhesive is developed as a way to remedy this problem. The single-chain structure of waterborne polyurethane (WPU) is transformed into a network structure by introducing the three-position network structure to increase the cohesive energy and heat resistance of the WPUPSA. Meanwhile, the primary chain of waterborne polyurethane (WPU) is modified by the reaction between pyromellitic dianhydride (PMDA) and isophorone diisocyanate (IPDI) to include an imide ring and a benzene ring with more stable structures and heat resistance. Characterization results of the prepared WPUPSA show that the thermo-tolerance index of the WPUPSA increases by 15.2% and the room temperature 180° peel strength and shear resistance of the WPUPSA increase by 80.9 and 231.8%, respectively. Meanwhile, the temperature corresponding to the maximum thermal decomposition rate of the samples is improved. More importantly, at 80 and 100 °C, the 180° peel strength and shear resistance of the modified samples are stronger than those of the unmodified samples. In addition, the energy storage modulus of WPUPSAs is also greater than the loss and increases with the increase of the frequency. Viscoelasticity dominates in the samples. This will provide new insight for the development of WPUPSAs in the field of high-temperature resistance.