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We propose a novel 2D material based on silicon haeckelite (Hck), whose structure contains a silicon atom arranged in a periodic pattern of pentagons and heptagons. Stacking the two layers gives rise to a planar geometry of the layers that compose it. This new structure presents a semiconductor character with a band gap of 0.17 eV. Furthermore, we studied CO2 reduction using molecular hydrogen to form formic acid, carbon monoxide, formaldehyde, methanol, and methane. All these have been studied theoretically at the Grimme D3BJ corrected TPSS/def2-SVP level. A massive biflake containing 132 Si atoms was used to model the Hck surface. According to the results, CO2 capture with Hck is a spontaneous step; in contrast, the same process for silicene mono- and bi-flakes studied previously was endergonic. After the capture of CO2, the addition of H2 to the substrate passes through an intermediate containing a Si–H bond. The formation of Si–H intermediates is the origin of the catalytic effect, facilitating H2 dissociation and acting as the hydrogen atom donor for the substrate. These intermediates are transformed by adding hydrogen atoms and losing water molecules, producing formic acid and formaldehyde as the most probable products, with rate-controlling steps of 29.2 and 27 kcal mol−1, whose values were less than those exhibited by the silicene biflake. This means that the silicon haeckelite biflake presents better catalytic activity than the silicene biflake. The results show that the novel 2D silicon hackelite material has remarkable potential for CO2 capture and reduction. The theoretical analysis of this innovative 2D structure provides valuable insights into the potential applications of silicene-based materials. [ABSTRACT FROM AUTHOR]

The use of renewable energy sources to reduce carbon dioxide (CO2) emissions has gained significant attention in recent years. The catalytic reduction of CO2 into value-added products is a promising approach to achieve this goal, and silicene biflakes (2Si) have been identified as potential candidates for this task. In this study, we explored the catalytic activity of these structures using density functional theory calculations. Our results show that the reaction pathway involves the adsorption of CO2 onto the silicene surface, followed by the addition of hydrogen molecules to form products such as formic acid, methanol, methane, carbon monoxide, and formaldehyde. Our proposed mechanism indicates that silicene biflakes exhibit a higher affinity for CO2 than single-layer silicon. We also found that the hydrogenation with H2 occurs by adding one hydrogen atom to the absorbed CO2 and another to the surface of 2Si. Intermediate species are reduced by systematically adding hydrogen atoms and removing water molecules, forming formic acid as the most probable product. The rate-controlling step for this reaction has an energy of 32.9 kcal mol−1. In contrast, the process without a catalyst shows an energy of 74.6 kcal mol−1, suggesting that the silicon bilayer is a structure with outstanding potential to capture and reduce CO2. Our study provides important insights into the fundamental mechanisms underlying the silicene-mediated CO2 reduction and could facilitate the development of more efficient catalysts for this process. [ABSTRACT FROM AUTHOR]

From density functional theory calculations, we elucidated the reaction mechanism of CO2 reduction on silicene nanoflakes. According to the results, silicene monoflakes present a notable catalytic activity for the hydrogenation of CO2. The most probable energetically favorable reaction pathway is formic acid and formaldehyde production, with energy barriers ranging between 16 and 24.1 kcal/mol. At the same time, transforming carbon dioxide to methanol, carbon monoxide, and methane requires higher activation energies. This theoretical perspective provides significant insights into silicene‐based materials and their potential applications as CO2 conversion to fuel and value‐added chemicals. [ABSTRACT FROM AUTHOR]

Introduction: The Unequal Area Facility Layout Problem (UA-FLP), is a problem of combinatory optimization no lineal, well known for looking for the best ordination of stations work that possess areas and/or distinct dimensions; recent studios show approximate methods, like metaheuristics, to resolve this type of problems, or in his defect show innovation in the modelacion mathematical of the same, fits to highlight that the effect of the decoders like variable of the problem had not been analyzed until this moment. Objective: Determine if it existed significant difference in the quality of the solution offered by each one of the combinations Metaheuristic-Decoder. Method: They proposed two metaheuristics, a Basic genetic algorithm and an algorithm called N2, to the equal that two decoders, the Decoder in spiral and the Decoder in blower, later realized a simple experiment whose experimental factor was the combination Metaheuristic-Decoder and the dependent variable was the objective function of the problem analyzed. Results: The experimental design showed that the combination, metaheuristic N2 and Decoder in spiral offer better quality results. Conclusions: It exists significant difference in the combination Metaheuristic- Decoder; in specific can affirm that for the problem in question, the metaheuristic N2 is more efficient than the Basic Genetic Algorithm, added to this, also can conclude that the decoders have big influence on the hour to resolve an UA-FLP. [ABSTRACT FROM AUTHOR]

Weinvestigate the electronic structure and noncovalent interactionswithin cation–radical complexes that are relevant in the electronimpact mass spectrometry of N-(2-furylmethyl)anilines,4-R–C6H4–NH–CH2–C4H3O with (R = −H, −OCH3, −CH3, −F, −Cl, −Br).In particular, we consider the reactive intermediates that precedethe final products of two previously suggested dissociation pathwaysfor these systems, i.e., (i) a direct cleavage of the NH–CH2bond and (ii) an isomerization/fragmentation mechanism. Thestudy is performed by means of correlated calculations (UCCSD andUMP2) together with density functionals (UM06 an UM06-2x) along withthe triple-ζ quality basis set 6-311++G(2d,2p). In addition,we carried out a topological analysis of the electron density in accordancewith the quantum theory of atoms in molecules (QTAIM) together withthe examination of the noncovalent interaction (NCI) index. In contrastwith previous studies based on the UB3LYP approximation, we coulddetermine the transition states associated with both fragmentationpathways. The Rice–Ramsperger–Kassel–Marcus theory,used to determine the relative importance of these dissociation mechanisms,indicates that whereas the direct cleavage and the isomerization/fragmentationreaction routes have similar constant rates at low energy, the formerprevails when the energy of the system is increased. The QTAIM analysisreveals that the charge of the cation–radical complex is mainlylocated on either a furfuryl (direct cleavage mechanism) or a pyrylium(isomerization/fragmentation pathway) ion and that these units interactwith a neutral radical aniline moiety. The localization of the positivecharge in either a furfuryl or pyrylium cation is in agreement withthe preminecence of the m/z= 81fragment in the mass spectrometry of N-(2-furylmethyl)anilines.Moreover, the QTAIM properties indicate that the α unpairedelectron of the system is principally distributed over the nitrogenand the orthoand paracarbon atomswith respect to the −NH group in the R–C6H4–NH unit. The investigation of the NCI indexand the intermolecular bond critical points and bond paths gives anaccount of the NCIs linking the radical cation clusters under consideration.Finally, we found correlations which indicate that the concentrationof the m/z= 81 fragment in a massspectrum is reduced with the interaction energy of the radical complexfrom which it is originated. Altogether, this work shows how the combinationof suitable electronic structure calculations along with post wavefunction analyses can yield important insights about the formationand properties of cation–radical complexes relevant in massspectrometry. [ABSTRACT FROM AUTHOR]

The energy-dependent branching ratios of the complementaryfragmentions [C5H5O]+and [HC6H4NH]+([M – C5H5O]+), originating from the N-(2-furylmethyl)anilinemolecular ion, [HC6H4NH–C5H5O]+•, were obtained from Rice–Ramsperger–Kassel–Marcus(RRKM) rate calculations based on density functional theory (DFT)energy profiles. The UB3LYP/6-311G+(3df,2p)//UB3LYP/6-31G(d) levelof theory was used to model the competitive reaction mechanisms bywhich the molecular ion can be fragmented. Initially, eight pairsof products were taken into account, corresponding to the combinationof two isomeric structures for each fragment ion and the concomitantradicals, which can be formed by direct dissociations or through someisomerization-fragmentation pathways. A great deal of the obtainedpathways was discarded by looking over the kinetic barrier heightsand the individual RRKM rate coefficients calculated for all the steps.This way, the potential energy profiles were simplified to only threereaction channels, two pathways to [C5H5O]+and one to [M – C5H5O]+. The pre-equilibrium and steady-state approximations were then appliedto different regions of the remaining potential energy profiles, allowingthe branching ratios of the complementary fragment ions to be easilycalculated and discriminated among the three rival processes. Accordingto these results, the major fragment ion in the ion source is [C5H5O]+, which is produced as a mixtureof two structures, the furfuryl and pyrylium cations, one formed bya direct C–N bond cleavage and the other through an isomerization-fragmentationchannel. In turn, the direct fragmentation is the only mechanism toproduce [M – C5H5O]+. To confrontthese results with the available experimental information, the modelwas broadened out to the 4-substituted analogues [4-R–C6H4NH–C5H5O]+•in which R = F, Br, Cl, CH3, and OCH3, findingexcellent correlations of the calculated branching ratios and therelative abundances in the electron ionization mass spectra. [ABSTRACT FROM AUTHOR]

We propose a novel 2D material based on silicon haeckelite (Hck), whose structure contains a silicon atom arranged in a periodic pattern of pentagons and heptagons. Stacking the two layers gives rise to a planar geometry of the layers that compose it. This new structure presents a semiconductor character with a band gap of 0.17 eV. Furthermore, we studied CO 2 reduction using molecular hydrogen to form formic acid, carbon monoxide, formaldehyde, methanol, and methane. All these have been studied theoretically at the Grimme D3BJ corrected TPSS/def2-SVP level. A massive biflake containing 132 Si atoms was used to model the Hck surface. According to the results, CO 2 capture with Hck is a spontaneous step; in contrast, the same process for silicene mono- and bi-flakes studied previously was endergonic. After the capture of CO 2 , the addition of H 2 to the substrate passes through an intermediate containing a Si-H bond. The formation of Si-H intermediates is the origin of the catalytic effect, facilitating H 2 dissociation and acting as the hydrogen atom donor for the substrate. These intermediates are transformed by adding hydrogen atoms and losing water molecules, producing formic acid and formaldehyde as the most probable products, with rate-controlling steps of 29.2 and 27 kcal mol -1 , whose values were less than those exhibited by the silicene biflake. This means that the silicon haeckelite biflake presents better catalytic activity than the silicene biflake. The results show that the novel 2D silicon hackelite material has remarkable potential for CO 2 capture and reduction. The theoretical analysis of this innovative 2D structure provides valuable insights into the potential applications of silicene-based materials.

The use of renewable energy sources to reduce carbon dioxide (CO 2 ) emissions has gained significant attention in recent years. The catalytic reduction of CO 2 into value-added products is a promising approach to achieve this goal, and silicene biflakes (2Si) have been identified as potential candidates for this task. In this study, we explored the catalytic activity of these structures using density functional theory calculations. Our results show that the reaction pathway involves the adsorption of CO 2 onto the silicene surface, followed by the addition of hydrogen molecules to form products such as formic acid, methanol, methane, carbon monoxide, and formaldehyde. Our proposed mechanism indicates that silicene biflakes exhibit a higher affinity for CO 2 than single-layer silicon. We also found that the hydrogenation with H 2 occurs by adding one hydrogen atom to the absorbed CO 2 and another to the surface of 2Si. Intermediate species are reduced by systematically adding hydrogen atoms and removing water molecules, forming formic acid as the most probable product. The rate-controlling step for this reaction has an energy of 32.9 kcal mol -1 . In contrast, the process without a catalyst shows an energy of 74.6 kcal mol -1 , suggesting that the silicon bilayer is a structure with outstanding potential to capture and reduce CO 2 . Our study provides important insights into the fundamental mechanisms underlying the silicene-mediated CO 2 reduction and could facilitate the development of more efficient catalysts for this process.