Critical Point Analysis Research Articles

ANALYSIS OF INDUSTRIAL FOOD PRODUCTION SYSTEMS TO ENSURE FOOD SAFETY AND QUALITY

To ensure the economic security of the country, it is necessary to ensure the safe production and processing of food products. This article reflects the analysis of hazards and critical control points (HACCP), as well as the analysis of the Food Safety Management System based on ST RK ISO 22000/ISO 22000. Food safety and quality assurance systems are essential to reduce risks and ensure compliance with the strictest standards. HACCP plays an important role in the food safety management system based on ISO 22000/ISO 22000 standards in the Republic of Kazakhstan, helping companies identify, assess and manage food-related hazards during their production, processing and distribution. An analysis of existing food production systems will identify opportunities for the development of more effective and comprehensive food safety and quality assurance systems. These improved systems will be vital to meet the growing needs and expectations of consumers, as well as to ensure safe and high-quality food products for future generations. By introducing HACCP and SMBPP at enterprises based on ISO 22000/ISO 22000 ST RK, food manufacturers can improve the safety and quality of their products.

Development of rational compositions for multicomponent juices based on melon crops

This study objects are juices from melon, watermelon, and pumpkin, as well as additives from apples, plums, pears, bell peppers, beets, carrots, aloe, melissa, and nettle. The problem addressed is minimizing melon crop losses. The research relevance stems from the need to reduce these losses. The development of multicomponent juices is aimed at the more efficient utilization of melon crops, contributing to the minimization of crop losses. Optimal component proportions were determined using sensory evaluation of organoleptic characteristics on a 5-point scale. The results showed that juice compositions with optimal component proportions have high organoleptic qualities and functional orientation. For melon juice, the optimal ratio was as follows: melon juice – 55 %, apple juice – 30 %, green bell pepper juice – 10 %, aloe juice – 5 %. For watermelon juice: watermelon juice – 65 %, plum juice – 25 %, beet juice – 5 %, melissa juice – 5 %. For pumpkin juice: pumpkin juice – 60 %, pear juice – 20 %, carrot juice – 15 %, nettle juice – 5 %. Critical control point (CCP) analysis was conducted at each production stage, from raw material acceptance to packaging and storage of the final product. This analysis identified potential risks and established control measures to minimize them. Developing multicomponent juices based on melon crops with plant-based enriching additives allows the creation of products with high organoleptic qualities and functional orientation, contributing to efficient use of melon crops and reducing crop losses. Implementing the HACCP system at all production stages ensures product safety and high quality. This research offers a practical approach for the food industry to produce high-quality, functional beverages that maximize crop yields and ensure consumer safety

In Situ Annealing Effect on Thermally Co-Evaporated CsPbI2Br Thin Films Studied via Spectroscopic Ellipsometry.

All-inorganic cesium lead halide perovskites possess excellent thermal stability, a feature that renders them highly favorable for optoelectronic applications with an elevated thermal budget. Employing a coevaporation approach for their deposition holds promise for manufacturing at an industrial level, owing to improvements in device scalability and reproducibility. For unlocking the full potential of vacuum-evaporated perovskite thin films, it is crucial to delve deeper into their crystallization process, which, as a solid-state reaction, has been less investigated compared to the crystallization process of, most commonly used, solution-based methods. In this work, we employ spectroscopic ellipsometry, a nondestructive, high speed, and high accuracy characterization method, to study the real time annealing effect on thermally coevaporated CsPbI2Br thin films in a temperature range between 25 and 300 °C. We achieve this by developing a singular dynamic model that can be fitted in real time as a function of temperature, providing insights into how thermal annealing influences the perovskite film's morphology and optical constants. Based on the latter, we derive the temperature dependence of the thermo-optic coefficient and Urbach energy as well as analyze the interband transition energies via critical point analysis. We demonstrate that the γ- to β-phase transition can be identified through a pronounced shift in the bandgap energy, whereas the β- to α-phase transition can be discerned by a sharp increase in the film's roughness. We corroborate the obtained fit results with additional in- and ex situ measurements, such as in situ grazing incidence wide-angle X-ray scattering, atomic force microscopy, reflectance/transmittance, and profilometry.

β-d-Glucopyranose – Silver+ (1:1) complex assisted aromaticity involving electron deficient X3 (X=Be, Mg) core

Seeing the frontier molecular orbitals (FMO) picture of β-d-glucopyranose–silver+ (1:1) complex ([Ag(C6H12O6)]+) reported in a recent article (Mondal, 2024) [53], we used the FMO based approach to obtain inverted sandwich like organometallic complex comprising X3 (X=Be, Mg) core, in silico. Thermodynamic feasibility of obtaining [(C6H12O6)Ag-X3-Ag(C6H12O6)] (X=Be, Mg) complexes are explored. Conceptual density functional theory (CDFT) based reactivity descriptors guide to ascertain the stability order of such complexes. By the help of natural bond orbital analysis, Wiberg bond indices (WBI), bond critical point analysis, electron density descriptors, and gradient isosurface between selected contacts, the nature of interaction between the X3 core and Ag metals are studied. FMO of the complexes further help in ascertaining the nature of binding. Energy decomposition analysis marks the interaction between X3 and Ag metals in [(C6H12O6)Ag-X3-Ag(C6H12O6)] (X=Be, Mg) as partially covalent. Negative values of nucleus independent chemical shift (NICS) at the triangular ring (X3) centres [NICS(0)] indicate aromatic property.

In-plane and out-of-plane anisotropy in the optical and dielectric properties of YBa2Cu3O7-x superconducting film

YBa2Cu3O7-x (YBCO) is a crucial aspect of research in the field of superconducting applications, where its high anisotropy is generally undesirable in strong power transmission. However, from a dialectical perspective, a thorough investigation of material anisotropy can offer an additional degree of freedom to tune potential properties and design innovative devices. This work employed pulsed laser deposition to fabricate a high-quality YBCO thin film (Tc = 89 K) and used the Mueller matrix spectroscopic ellipsometer (MMSE) to determine the complete dielectric tensor of the YBCO film across the ultraviolet to near-infrared spectrum (245–1000 nm), enabling a comprehensive, quantitative study of the optical anisotropy of YBCO. It provided optical constants and dielectric function spectra for different axes. We found that YBCO exhibits birefringence and dichroism both in-plane and out-of-plane. By combining standard critical point (SCP) analysis and first-principles calculations, we identified specific interband transitions related to SCP in the YBCO dielectric spectra, revealing the physical essence of anisotropic optical transitions from a quantum mechanical standpoint. Temperature-dependent studies of the transitions and optical constants were conducted. The work fills a partial void in the optical parameters of the anisotropy of YBCO and holds relevance for understanding the origins of copper-based high-temperature superconductivity.

Adsorption and dissociation of NO on gold–palladium alloy clusters: A density functional theory study

Alloy nanoclusters often exhibit distinctive and exceptional performance, making them especially appealing as catalysts. In this study, the adsorption and dissociation of NO on AumPdn (m + n = 8) clusters was studied using density functional theory (DFT). The most stable structures of AumPdn (m + n = 8) clusters were reported by the CALYPSO search screening program and DFT geometric optimization. The binding energy and bond critical point (BCP) analysis show that alloying could lead to a more compact structure and relatively stronger stability. Molecular electrostatic potential (MESP) analysis revealed that the optimal site for the adsorption of the NO molecule on AumPdn (m + n = 8) clusters was at the top site, with Pd atoms being the preferred choice. Projected density of states (PDOS) calculations demonstrate that the d-band center of the Au5Pd3 cluster was closest to the Fermi level, enhancing the interaction between the cluster surface and adsorbed molecules. The activation energy of NO dissociation on the Au5Pd3 surface is the lowest at 0.48 eV. These findings indicate that the Au5Pd3 nano-alloy cluster shows promise as an effective catalyst in the direct transformation of NO into non-toxic substances.

Risk analysis of critical control points of Staphylococcus aureus in layer farms and chicken egg distributors.

Microbiological criteria play a role in verifying the critical control points (CCP), which become part of the hazard analysis, and the CCP system that guarantees quality, considering possible danger points or stages in the food production chain. Studies about Staphylococcus aureus in chicken eggs more extensively discuss the path, source, and level of prevalence of contamination at the final distributor or consumer. Therefore, this study investigates CCP contamination of S. aureus in chicken eggs and their potential consumption, which could endanger human health from the layer farm until the final distributor. This study is critical in health, public health, and veterinary medicine for preventing and controlling consumers' security. This study done for CCP on the chain distribution of chicken eggs starts with preparing production and distribution process flow diagrams for livestock, agents/wholesalers, and retailers. Confirmation of operational production in the field/location study is based on the flow chart that has been arranged, identifying all potential dangers associated with each stage and analyzing potential risks considering every action for controlling identified hazards. The next step involves pinpointing the CCP to counteract the identified threat. An application tree decision defines the CCP, and the logical and final approach is the determination limit critical to the CCP. Analysis results in the determination of CCP contamination of S. aureus, indicating that chicken eggs, personal hands (farm workers, wholesalers, and retailers), shelf eggs, and feces are CCP on farms.

Determining Critical Points in Fish Distribution and Calculation of Income UD. Sumber Rezeki Laut, Tuban Regency

This study aims to evaluate the fish distribution activities in UD. Sumber Rezeki Laut, alongside the fish handling during distribution, and critical points of fish quality decline during distribution. This research uses descriptive analysis, critical point analysis, organoleptic tests, and income analysis. Distribution handling is divided into two types, namely direct distribution handling and indirect distribution handling. The most important handling of both types of distribution includes maintaining the right temperature during the process, transferring fish to UD. Sumber Rezeki Laut, changing fish containers, cleaning and soaking fish, and distributing fish to Balekambang Market. However, the long travel distance required to distribute the fishes has the potential to reduce the quality of the fish, as evidenced by the decrease in fish quality observed during the distribution trials. Organoleptic test results showed that the quality of the fish decreased from when it was purchased until it reached the wholesaler. Meanwhile, when calculating distribution costs, the highest result for direct distribution was IDR1,335,987, and the lowest was IDR372,995. The highest income from indirect distribution was IDR1,544,001, while the lowest was IDR399,993. To ensure good fish quality, UD. Sumber Rezeki Laut needs to improve its human resource capabilities to become more efficient and produce quality products for consumers.

Dielectric function and interband critical points of compressively strained ferroelectric K0.85Na0.15NbO3 thin film with monoclinic and orthorhombic symmetry

The dielectric function and interband critical points of compressively strained ferroelectric K0.85Na0.15NbO3 thin film grown by metal-organic vapor phase epitaxy (MOVPE) are studied in broad spectral and temperature ranges by spectroscopic ellipsometry (SE). The temperature dependence of the measured pseudodielectric functions is strongly affected by a structural phase transition from the monoclinic Mc-phase to the orthorhombic c-phase at about 428 K. Using a parametric optical constant model, the corresponding dielectric functions as well as the interband optical transitions of the film are determined in the spectral range of 0.73–6.00 eV. Standard critical point (SCP) analysis of the 2nd derivatives of the dielectric functions identified three and four critical points for monoclinic and orthorhombic symmetries, respectively. A systematic redshift of the threshold energies with increasing temperatures was observed.

An analogue on/off state-switching control method suitable for inverter-based air conditioner load cluster participating in demand response

With the significant trend towards variable frequency in heating ventilating and air-conditioner (HVAC) loads, the inverter-based air conditioner load (IACL) clusters are poised to become the mainstay in participating in demand response (DR). During the process of DR, once the indoor temperature exceeds the comfort constraint, HVAC load must be forced to exit DR, which brings correlation to the behaviour of the preceding and following periods, making cluster optimization modelling and solution difficult. In order to solve the problems, this paper proposes an analogue ON/OFF state-switching (AOSS) control method suitable for IACL cluster participating in DR. Firstly, the critical working point corresponding to the comfort constraint is analysed for eliminating the temporal coupling for IACL. Then, an AOSS control method is proposed based on the critical point analysis. The feasibility of the proposed AOSS control is validated by the experimental results, with the Hisense KFR-75W/T08SBp-A2 inverter-based air conditioning DR experimental platform. Furthermore, by using the proposed AOSS control, a day-ahead scheduling model is constructed, and, the traditional state-queuing (SQ) model is transplanted to the IACL cluster for short-term power control. And the case studies verified the effectiveness and applicability of the day-ahead scheduling model and the transplanted SQ model.

Density functional study of the electronic, bonding, elastic and infrared properties of tetragonal H2O2 ice

Hydrogen peroxide is one of the most important commercially used oxidant and exists widely in the environment. It crystallizes in a tetragonal phase via hydrogen bond at around −0.89 °C. However, many of its fundamental properties are still not well studied. To investigate systems containing hydrogen bond, van der Waals correction must be considered. In this work, we tested a series of local and non-local van der Waals corrections within the frame of density functional theory. The optPBE-vdW and the vdW-DF-CX functionals are found to be the best ones based on the relaxed lattice parameters. Then the electronic, bonding, elastic, infrared, piezoelectric and dielectric properties are studied and discussed. The results reveal that tetragonal H2O2 is an indirect band gap insulator. Bond critical point analysis, reduced density gradient analysis and crystal orbital Hamilton population analysis uncover that the H-O···H bonds are moderate hydrogen bonds, which contribute most to the formation of the crystal. The interactions between the O atoms of neighbouring H2O2 molecules also have a bit contribution. Elastic stability of tetragonal H2O2 is confirmed and its elastic anisotropy is illustrated by directional bulk and shear moduli. The vibrational modes at the Brillouin zone center are assigned, and their frequencies and eigen-displacements are calculated. Additionally, its infrared spectrum is simulated. Its Born effective charges, piezoelectric and dielectric coefficients are also obtained and discussed.

Thermodynamic analysis of anomalous region, critical point, and transition from subcritical to supercritical states: Application to van der Waals and five real fluids

All fluids exhibit large property-variations near the critical point in a region identified as the anomalous state. The anomaly starts in the liquid and extends well into the supercritical state, which can be identified thermodynamically using the Gibbs free energy (g). The specific heat, isobaric expansion, and isothermal compressibility parameters governing the transitions are: (cp/T), (vβ), and (vκ), rather cp, β, and κ. They are essentially the second-order derivatives of g and have two extrema (minimum, maximum); only maxima reported ever. When applied to the van der Waals fluid, these extrema exhibit closed loops on the phase-diagram to satisfy d3g = 0 and map the anomalous region. The predicted liquid-like to gas-like transitions are related to the ridges reported earlier, and the Widom delta falls between these loops. Evidently, in the anomalous region, both the liquid and the supercritical fluid need to be treated differently. Beyond the anomalous states, the supercritical fluids show monotonic, gradual changes in their properties. The analysis for argon, methane, nitrogen, carbon dioxide, and water validates the thermodynamic model, supports the stated observations, and identifies their delimiting pressures and temperatures for the anomalous states. It also demonstrates the applicability of the law of corresponding states. Notably, the critical point is a state where d3g = 0, the anomaly in the fluid's properties/behavior is maximal, and the governing parameters approach infinity. Also the following are presented: (a) the trajectory of the liquid–vapor line toward the melt-solid boundary and (b) a modified phase diagram (for water) exhibiting the anomalous region.

A unified friction factor formulation: Bridging laminar and turbulent friction factor with critical points analysis

The friction factor is widely recognized as a pivotal parameter in the analysis of fluid–boundary interactions; however, a comprehensive grasp of friction mechanics remains elusive. This investigation revisits measurements from the benchmark Nikuradse measurements, furnishing indirect evidence of two critical points in pipe turbulence. It underscores that friction factors within laminar and turbulent regimes are intimately interconnected, bearing significant relations to subcritical and critical phenomena. The two critical points directing the laminar–turbulent transition consist of a standard non-equilibrium phase transition and a fully matured turbulent regime, accompanied by an extensive crossover to its asymptotic scaling. Relying on a mathematical model, the scaled friction factor for rough pipes converges into a unified curve. New formula of friction factor of pipe flow is derived, and it was illustrated that it can be derived as a geometric weighted parameter, bridging the laminar and turbulent friction factors. Conclusively, the proffered model was juxtaposed with pipe experimental data from the antecedent study and more contemporaneous transitional pipe data to authenticate the aptness of the suggested model, and it united the friction factor in all three regimes.

Unravelling ionic liquid solvent effects for a non-polar Cope rearrangement reaction.

The impact of ionic liquids (ILs) on polar reactions is well recognised, however the impact of ILs on non-polar reactions is less well understood or explored. Pericyclic Cope rearrangements are highly concerted, exhibit minimal charge localisation and pass through an uncharged but well-defined transition state, and thus provide a good mechanism for exploring the impact of IL polarizability on chemical reactivity. Recently, a 10× rate enhancement has been observed for the Cope rearrangement of 3-phenyl-1,5-hexadiene in the IL 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [C4C1im][NTf2] compared to benzene. In this work we undertake a DFT based computational study (B3LYP-D3BJ/6-311+G(d,p) and M06-2X-D3/6-311+G(d,p)) of the Cope rearrangement of 3-phenyl-1,5-hexadiene and 3-propyl-hexa-1,5-diene in molecular solvents (acetonitrile, benzene and ethanol) and the IL [C4C1im][NTf2] using the SMD solvation model. The impact of benzene and [C4C1im][NTf2] on the Cope rearrangement of 3-phenyl-1,5-hexadiene is studied in more detail and we provide insight into the reason for the rate enhancement in an IL. The volume of activation is evaluated and the potential impact of 'solvent pressure' is discussed. We identify two potential mechanisms for volume effects to contribute to the rate enhancement. Solvent association energies are evaluated at the DLNPO-CCSD(T) level. Specific solvent interactions are explored through atomic partial charge, molecular orbital and bond critical point analysis, as well as via non-colvalent interaction (NCI) plots, electrostatic potential (ESP) differences and density difference Δρ(r) plots. We find that the cation and anion together form an extensive van der Waals pocket in-which the transition state (TS) sits. Electron density within the TS is anisotropically polarised via a 'push-pull' effect due to the dual cation-anion nature of the IL, stabilising the TS relative to benzene. We also provide experimental evidence that these effects are generalisable to other ILs. Overall, our aim is to provide a deeper moleuclar level understanding of the impact of ILs on non-polar reactions.

Temperature‐Dependent Excitonic Band Gap in Lead‐Free Bismuth Halide Low‐Dimensional Perovskite Single Crystals

AbstractIn this study, the optical behavior of lead‐free Bi‐based low‐dimensional perovskite single crystals (Cs3Bi2Cl9, Cs3Bi2Br9, Cs3Bi2I9, and MA3Bi2I9) is investigated by spectroscopic ellipsometry, supported by X‐ray diffraction and density functional theory calculations. All materials exhibit a strong excitonic peak resulting from photogenerated electron–hole Coulomb interactions, whereas the threshold of continuous absorption is found at higher energies. The resonances of the excitonic and continuous bands, along with exciton binding energies, are extracted through Critical Point Analysis of the ellipsometric data over a wide temperature range (from −90 °C to 90 °C), revealing subtle variations in the optical characteristics for each single crystal. These materials can be applied in optoelectronics as photodetectors because of their high stability and lower toxicity compared to their Pb‐based perovskites.

Food safety and the approach of the Human Milk Collection Center at the Hospital Zonal General de Agudos “Prof. Dr. Ramón Carrillo”

Introduction: Human milk banks are vital institutions for maternal and child health, promoting breastfeeding and neonatal care by processing and distributing donated breast milk. These banks contribute significantly to public and neonatal health by reducing medical complications and associated costs. In addition, they support maternal and child health policies, improving the quality of life of infants and reducing infant mortality. They are also fundamental for medical research on breast milk and its impact on infant health.Objective: To describe the implementation of a Critical Control Point analysis plan to ensure safe handling and increased volume of raw human milk.Methods: An observational and descriptive study was conducted in the milk bank, observing and documenting daily procedures and interviewing personnel. Internal documents were analyzed and a qualitative approach was applied to identify patterns and good practices.Results: Preventive and precautionary measures were implemented to ensure food safety, including Good Manufacturing Practices (GMP) and Standard Operating Procedures for Cleaning and Disinfection (SSOP). Critical points such as personnel hygiene and storage temperature were controlled. Traceability from donor to recipient was maintained, ensuring that raw and pasteurized milk was properly labeled. A health services network was established with the HIGA San Martin de La Plata Milk Bank to distribute pasteurized milk equitably.Conclusions: The HIGA Prof. Dr. Ramon Carrillo HIGA milk bank has been successful in maintaining food security and increasing the availability of raw and pasteurized human milk. Despite challenges such as a building renovation, a rigorous control of critical points has been maintained. Cooperation with the HIGA San Martin Milk Bank has facilitated the equitable distribution of pasteurized milk. This report highlights the success in ensuring food security and access to breast milk for the most vulnerable newborns.

Quantitatively Exploring Giant Optical Anisotropy of Quasi-One-Dimensional Ta2NiS5.

Optical anisotropy offers a heightened degree of flexibility in shaping optical properties and designing cutting-edge devices. Quasi-one-dimensional Ta2NiS5, with giant optical anisotropy, has been used in the development of new lasers and sensors. In this research endeavor, we successfully acquired the complete dielectric tensor of Ta2NiS5, utilizing the advanced technique of Mueller matrix spectroscopic ellipsometry, enabling a rigorous quantitative assessment of its optical anisotropy. The results indicate that Ta2NiS5 demonstrates giant birefringence and dichroism, with Δnmax = 1.54 and Δkmax = 1.80. This pursuit also delves into the fundamental underpinnings of this optical anisotropy, drawing upon a fusion of first-principles calculations and critical points analysis. The anisotropy of Ta2NiS5 arises from differences in optical transitions in different directions and is shown to be due to van Hove singularities without exciton effects. Its giant optical anisotropy is expected to be useful in the design of novel optical devices, and the revelation of the physical mechanism facilitates the modulation of its optical properties.

Edukasi Titik Kritis Kehalalan Produk Pangan, Kosmetik, dan Obat-Obatan Menggunakan Flowchart pada Siswa Sekolah Menengah Analis Kimia (SMAKPA) Padang

Halal products are crucial for consumers. In Islam, halal and wholesome food consumption is vital for maintaining physical and spiritual well-being. The Indonesian government mandates halal product certification by Law No. 33 of 2014 on Halal Product Assurance. The critical points in determining the halal status of a product refer to processes or ingredients in its production that may potentially involve, contain, or mix with haram substances. Nevertheless, many students lack a clear understanding of halal and haram principles. This knowledge is essential to help students avoid using forbidden ingredients in Islamic teachings. Padang Chemical Analyst High School (SMAKPA) students are the targets of this service because vocational school students must have work-ready skills. Before the education session, a pre-test was conducted to assess the student's understanding of the material presentation. Education was delivered using a flowchart to enhance engagement and comprehension. The content encompasses the concepts of halal and haram in Islam, the responsible parties for halal certification, halal logos, and the analysis of critical points in the halal status of food, cosmetics, and medications. Following the material presentation, a post-test was administered, followed by a question and answer session to evaluate the students' understanding. Pre-tests and post-tests were employed to assess student comprehension, with pre-test scores averaging 99 and post-test scores at 99.5. Through this educational initiative, students gain a comprehensive understanding of the Critical Points of Halal Status in Food, Cosmetics, and Medications using a flowchart

Stability of lithium boron carbides with defective chains and a new phase from strain-induced phase transition

The new chain structures of the main o-LiB13C2 crystal with (C-B-C) chain are proposed to obtain new structures. The structural, mechanical, electronic, and dynamic properties of the newly designed structures with the B12(X-Y-X) and B12(X-X) (X and Y = B, C, and N) formulae are investigated by the first principles of density functional theory (DFT), and detailed comparisons with the main crystal between the stable and unstable structures are given. It is found that the structures with (N-C-N), (C-Va-C), and (N-Va-N) chains meet the thermodynamic, mechanical, and dynamic stability conditions. The tensile strengths of the stable structures are examined, and it is observed that the (N-C-N) chain system underwent a phase change and turned into a new stable structure that has an (N-Li-N) chain and different bonding geometry and characteristics in interstitial space between the B12 icosahedra. A detailed geometry analysis utilizing the selected bond lengths, volume and surface area of B12 icosahedron is offered. The partial density of states, charge and critical point analysis, electron density differences are presented to clarify the bonding situations of the structures. The Bader charges of B12 icosahedra in the stable structures have positive, in contrast to Wade’s rule. The existence of the chain in the B12(X-Y-X) and B12(X-X) compounds affects the charging behavior of B12 icosahedron due to the different asymmetrical charge densities. The mechanical properties and their anisotropies are calculated for different lattice directions and visualized through 2D and 3D graphs. Based on the actual bonding characteristics, the bond resistance model with Phillips ionicity and Mulliken bond overlap populations, the bond electronegativity model, and the bond valence model, the hardnesses of the stable structures are calculated by each model. It is found that the stable structures have hardnesses spanning a wide range of 8–35 GPa due to the different models. The origin and dynamic instability of the unstable structures are examined. It is concluded that the existence of Li atoms and different chains, which include the different electronegativity of atoms within the structure, have essential roles in charge transfers, chain geometries, vibrational behavior, and then the stability of the structures.

Enhancement of nonlinear optical properties of nanocarbon cluster C60 by aluminum doping

AbstractThe search for good nonlinear optical (NLO) materials is of utmost importance in laser technology and optical information science, making it a popular research topic in materials science. It is reported that the introduction of alkali metal Li can enhance the NLO properties of nanocarbon materials. Here, metal Al, which exhibits similar electron transfer characteristics to Li, was used for the first time to enhance the NLO properties of nanocarbon cluster C60, which possesses a large delocalized π structure and the highest yield in the fullerene family. Density functional theory calculations in combination with Boltzmann distribution showed that the most thermodynamically stable Al@Ih(1812)‐C60 exhibited good second‐order NLO properties, which originated from the noncentrosymmetry geometry and one extra delocalized electron on Ih(1812)‐C60 from the 3p shell of inner Al. Density of state analysis indicated that the molecular orbitals of Al@Ih(1812)‐C60 were primarily formed by Ih(1812)‐C60 with minimal Al participation, and the presence of Al always resulted in an antibonding orbital effect. Bond critical point and electron localization function analyses indicated almost no covalent interaction between Al and Ih(1812)‐C60. Exohedral functionalization was employed to further stabilize Al@Ih(1812)‐C60 with radical character, and the infrared spectrum was also analyzed in detail. This study has promising implications for expanding the potential applications of fullerenes in optical devices.