Search

This work presents a systematic Raman scattering study and first-principles calculations for the EuB(6) system. Evidence for the presence of an incipient (∼1 × 10(-4) Å) tetragonal symmetry break of its crystalline structure was found. Forbidden Raman modes at ω(fRm(1))∼1170 cm(-1), ω(fRm(2))∼1400 cm(-1), and ω(fRm(3))∼1500  cm(-1) were observed. The tetragonal symmetry of ω(fRm(2)) and ω(fRm(3)) together with spin-polarized first-principles simulations of the structural and magnetic properties fully support such a break of symmetry. Our data and calculations explain the occurrence of ferromagnetism in Eu hexaborides, previously reported.

One class of the Ziegler-Natta catalysts (ZNC) - the TiCl 4 /MgCl 2 having triethyl aluminum (AlEt 3 ), has been widely utilized during ethylene polymerization. Although the Ti species plays the role of a major active site, an increase of Ti species does not always improve the activity of ZNC. Herein, investigations of experiments and density functional theory (DFT) elucidate this inverse effect of the increased amount of TiCl 4 deposition in ZNC because of the pretreatment process. However, the activity of ZNC on pretreated MgCl 2 dropped to 60% of the unpretreated one. The DFT demonstrates that the pretreatment strengthened the interaction between TiCl 4 and ZNC, especially on the (104) surface, forming the TiCl 4 -TiCl 4 cluster. The existence of this TiCl 4 -TiCl 4 cluster found on the ZNC (104) surface weakens the adsorption of the first AlEt 3 molecule and obstructs further alkylation process, making another Ti site of the alkylated TiCl 4 -TiCl 4 cluster inactive. However, the difficult formation of the TiCl4-TiCl4 cluster found on the ZNC (110) is an important key point that enables the activation of all adsorbed TiCl 4 on this surface by facilitating the alkylation process. Moreover, the existence of the MgCl 2 (110) surface prevents the formation of the TiCl 4 -TiCl 4 cluster significantly. Hence, it is suggested that the existence of the (110) plane on ZNC plays a key role in controlling the performance of the ZNC, especially the stability via the prevention of deactivation caused by the clustering of TiCl 4 ., (© 2024. The Author(s).)

The cubic α-CsPbI 3 phase stands out as one of the most promising perovskite compounds for solar cell applications due to its suitable electronic band gap of 1.7 eV. However, it exhibits structural instability under operational conditions, often transforming into the hexagonal non-perovskite δ-CsPbI 3 phase, which is unsuitable for solar cell applications because of the large band gap (e.g., ∼2.9 eV). Thus, there is growing interest in identifying possible mechanisms for increasing the stability of the cubic α-CsPbI 3 phase. Here, we report a theoretical investigation, based on density functional theory calculations, of the surface passivation of the α-, γ-, and δ-CsPbI 3 (100) surfaces using the C 6 H 4 (NH 3 ) 2 [ p -phenylenediamine (PPD)] and Cs species as passivation agents. Our calculations and analyses corroborate recent experimental findings, showing that PPD passivation effectively stabilizes the cubic α-CsPbI 3 perovskite against the cubic-to-hexagonal phase transition. The PPD molecule exhibits covalent-dominating bonds with the substrate, which makes it more resistant to distortion than the ionic bonds dominant in perovskite bulks. By contrasting these results with the natural Cs passivation, we highlight the superior stability of the PPD passivation, as evidenced by the negative surface formation energies, unlike the positive values observed for the Cs passivation. This disparity is due to the covalent characteristics of the molecule/surface interaction of PPD, as opposed to the purely ionic interaction seen with the Cs passivation. Notably, the PPD passivation maintains the optoelectronic properties of the perovskites because the electronic states derived from the PPD molecules are localized far from the band gap region, which is crucial for optoelectronic applications.

Two-dimensional (2D) Janus structures offer a unique range of properties as a result of their symmetry breaking, resulting from the distinct chemical composition on each side of the monolayers. Here, we report a theoretical investigation of 2D Janus Q ' A ' AQ P 3 m 1 monochalcogenides from group IV ( A and A ' = Ge and Sn; Q , Q ' = S and Se) and 2D non-Janus QAAQ P 3̅ m 1 counterparts. Our theoretical framework is based on density functional theory calculations combined with maximally localized Wannier functions and tight-binding parametrization to evaluate the excitonic properties. The phonon band structures exhibit exclusively real (nonimaginary) branches for all materials. Particularly, SeGeSnS has greater energetic stability than its non-Janus counterparts, representing an outstanding energetic stability among the investigated materials. However, SGeSnS and SGeSnSe have higher formation energies than the already synthesized MoSSe, making them more challenging to grow than the other investigated structures. The electronic structure analysis demonstrates that materials with Janus structures exhibit band gaps wider than those of their non-Janus counterparts, with the absolute value of the band gap predominantly determined by the core rather than the surface composition. Moreover, exciton binding energies range from 0.20 to 0.37 eV, reducing band gap values in the range of 21% to 32%. Thus, excitonic effects influence the optoelectronic properties more than the point-inversion symmetry breaking inherent in the Janus structures; however, both features are necessary to enhance the interaction between the materials and sunlight. We also found anisotropic behavior of the absorption coefficient, which was attributed to the inherent structural asymmetry of the Janus materials., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Purpose: To investigate the discordance in sarcoma diagnoses between nonspecialized institutions following revision by dedicated sarcoma pathologists at a reference center in Brazil and the relevance of molecular pathology in this context., Methods: We conducted a retrospective analysis of sarcoma samples initially analyzed at outside laboratories and subsequently reviewed by two specialized pathologists between January 2014 and December 2020. After obtaining demographic and tumor characteristics, pathology results were matched and classified as complete discordance (CD; benign v malignant, sarcoma v other malignancies), partial concordance (similar diagnosis of connective tumor, but different grade/histological subtype/differentiation), and complete concordance (CC). The concordance for histology or grade, and the role of molecular assessments supporting the diagnosis were also independently determined. Statistical analyses were conducted through the kappa coefficient of agreement and adherence by χ 2 test, χ 2 test by Person, and Fisher exact test., Results: In total, 197 cases were included, with samples obtained predominately from male patients (57.9%) and localized/primary tumors (86.8%). Following revision, the most frequent final diagnoses were undifferentiated pleomorphic sarcoma (17.8%), well-differentiated/dedifferentiated liposarcoma (8.6%), and leiomyosarcoma (7.6%). CD was found in 13.2%, partial discordance in 45.2%, and CC in 41.6% of reviews ( P < .001). We found a concordance for histology or grade of 53.5% ( P < .001) and 51.8% ( P < .001), respectively. Molecular assessments, comprising next-generation sequencing panels (79.5%) and fluorescent in situ hybridization (20.5%), were performed in 44 (22.3%) cases, with findings classified as of diagnostic relevance in 31.8%., Conclusion: In nearly 60% of the cases, the initial sarcoma diagnosis was modified when revised by a reference center and dedicated pathologists, assisted by molecular pathology techniques. These results justify the assembly of referral networks in countries with limited health care resources.

Improving the catalytic performance of materials based on cerium oxide (CeO2) for the activation of methane (CH4) can be achieved through the following strategies: mixture of CeO2 with different oxides (e.g., CeO2-La2O3) and the use of particles with different sizes. In this study, we present a theoretical investigation of the initial CH4 dehydrogenation on (La2Ce2O7)n clusters, where n = 2, 4, and 6. Our framework relies on density functional theory calculations combined with the unity bond index-quadratic exponential potential approximation. Our results indicate that chemical species arising from the first dehydrogenation of CH4, that is, CH3 and H, bind through the formation of C-O and H-O bonds with the clusters, respectively. The coordination of the adsorption site and the chemical environment plays a crucial role in the magnitude of the adsorption energy; for example, species adsorb more strongly in the low-coordinated topO sites located close to the La atoms. Thus, it affects the activation energy barrier, which tends to be lower in configurations where the adsorption of the chemical species is stronger. During CH4 dehydrogenation, the CH3 radical can be present in a planar or tetrahedral configuration. Its conformation changes as a function of the charge transference between the molecule and the cluster, which depends on the CH3-cluster distance. Finally, we analyze the effects of the Hubbard effective parameter (Ueff) on adsorption properties, as the magnitude of localization of Ce f-states affects the hybridization of the interaction between the molecule and the clusters and hence the magnitude of the adsorption energies. We obtained a linear decrease in the adsorption energies by increasing the Ueff parameter; however, the activation energy is only slightly affected., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

The combination of ceria (CeO 2 ) with different metal oxides ( M O 2 ), e.g. Ce 1- x M x O 2 , has been strategically used to enhance its intrinsic properties. Moreover, the controlled synthesis of mixed oxide nanoparticles (NPs) opens the opportunity to explore the size dependence and chemical composition of the physical-chemical properties. However, our atomic-level understanding of how the physical-chemical and thermodynamic characteristics change with particle size and composition remains far from satisfactory. Here, we used force-field molecular dynamics simulations to investigate the effects of composition ( x ) and size on the physical-chemical properties of Ce 1- x Zr x O 2 NPs with diameter from 1 (32 cations) up to 3 nm (256 cations), where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0. We found abrupt changes in potential energy versus temperature for NPs with more than 108 cations, indicating a structural phase transition from disordered to ordered structures, which was confirmed by the radial distribution function. We found a linear relationship between the phase transition temperature ( T pt ) and the size and composition of the NPs: the increase in the molar fraction of Zr 4+ and the reduction in particle size are related to lower T pt temperature and less defined decays of potential energy versus temperature. NPs larger than 56 cations show a radial distribution function with several peaks, which is related to the order of cations and anions in these structures. These peaks gradually disappear as the size decreases and the fraction of Zr 4+ increases. Similar trends were observed with X-ray diffraction analysis; for example, fluorite-like motifs occur even with 56 cations in the case of ceria, but only for NPs with 108 cations for zirconia. Common neighbor analysis confirmed that NPs with well-defined values of the temperature T pt have face-centered cubic (fcc)-like domains in the core region. The number of ordered fcc cations increases with increasing NP size and decreasing Zr 4+ concentration. Finally, we observed that ceria nucleate first during simulated annealing and occupy highly coordinated sites within the core, while Zr 4+ prefers the lowest coordinated sites on the surface.

The incorporation of chiral molecules (A) in materials based on hybrid ABX 3 perovskites has opened new paths to tune the optoelectronic properties of perovskites through the transfer of chirality to the inorganic BX framework. However, our atomistic understanding of the role of chemical BX composition in the magnitude of the chirality transfer is far from complete. In this study, we use density functional theory calculations and the experimental Ruddlesden-Popper chiral ( R -/ S -NEA) 2 PbBr 4 structure ( R -/ S -NEA = R -/ S -1-(1-naphthyl)ethylammonium) to investigate the effects induced by chemical substitution of Pb by Ge or Sn and Br by Cl or I on the transfer of chirality and physical-chemical properties. We have observed that different enantiomers result in opposing orientations of octahedral tiltings within the inorganic framework, thus transferring chirality to the inorganic structure. The tilts are greater in perovskites based on Pb and decrease in the sequence of Cl to Br to I, as a consequence of the decrease in the halide electronegativity that weakens the interactions between X and the -N + H 3 group of the NEA chiral cation. The chirality transfer is also evident in the Rashba-Dresselhaus effects on the electronic band structure, in which we found magnitudes directly correlated to the trends of octahedra tilting. The band offsets of substitutions B and X are predominantly influenced by their natural atomic energy levels, while organic molecules play a pivotal role in modulating the ionic potential and electron affinity in systems containing light atoms. The band gap values range from 1.91 up to 3.77 eV, with chirality and anion electronegativity providing significant tuning effects on whether the band gaps are direct or indirect.

Green hydrogen, generated through the electrolysis of water, is a viable alternative to fossil fuels, although its adoption is hindered by the high costs associated with the catalysts. Among a wide variety of potential materials, binary nickel-palladium (NiPd) systems have garnered significant attention, particularly at the nanoscale, for their efficacious roles in catalyzing hydrogen and oxygen evolution reactions. However, our atom-level understanding of the descriptors that drive their energetic stability at the nanoscale remains largely incomplete. Here, we investigate by density functional theory calculations the descriptors that drives the stability of the Ni m Pd n - m clusters for different sizes ( n = 13, 27, 41) and compositions. To achieve our goals, a large number of trial configurations were generated and selected using data mining algorithms ( k -means, t-SNE) and genetic algorithms, while the most important physical-chemical descriptors were identified using Spearman correlation analysis. We have found that core-shell formation, with the smaller Ni atoms lying in the center of the particle, plays a major role in the stabilization of the nanoalloys, and this effect causes the alloys to assume a icosahedral-fragment configuration (as the unary nickel cluster) instead of a fcc fragment (as the unary palladium cluster). However, the core-shell formation in this alloy is unique in that Pd poor compositions exhibit scattered Pd atoms on the surface. As the palladium content increases, this gives rise to the complete Pd shell. This stabilization mechanism is quantitatively supported by the different correlations observed in the number of Ni-Ni and Pd-Pd bonds with energy, in which the latter tends to decrease alloy stability. Furthermore, a notable trend is the correlation between the coordination number of Ni atoms with alloy stabilization, while the coordination of Pd atoms shows an inverse correlation.

We report a theoretical investigation of temperature, size, and composition effects on the structural, energetic, and electronic properties of the (La4O6)n, (La2Ce2O7)n, and (Ce4O8)n nanoclusters (NCs) for n = 10, 18. Furthermore, we investigated the single O vacancy formation energy as a function of the geometric location within the NC. Our calculations are based on the combination of force-field molecular dynamics (MD) simulations and density functional theory calculations. We identified a phase transition from disordered to ordered structures for all NCs via MD simulations and structural analysis, e.g., radius changes, radial distribution function, common neighbor analysis, etc. The transition is sharp for La36Ce36O126, La20Ce20O70, and Ce72O144 due to the crystalline domains in the core and less abrupt for Ce40O80, La40O60, and La72O108. As expected, radius changes are abrupt at the transition temperature, as are morphological differences between NCs located below and above the transition temperature. We found a strong dependence on the O vacancy formation energy (Evac) and its location within the NCs. For example, for La40O60, Evac decreases almost linearly as the distance from the geometric center increases; however, the same trend was not observed for Ce40O80, while there are large deviations from the linear trend for La20Ce20O70. Evac has smaller values for Ce40O80 and higher values for La40O60, that is, almost three times, while Evac has intermediate values for mixed oxides, as expected from weighted averages. Therefore, the mixture of one formula unit of La2O3 with two formula units of CeO2 has the effect of increasing the stability of CeO2 (binding energy), which increases the magnitude of the formation energy of the O vacancy., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Electrocatalytically reducing CO2 into value-added products is a challenging but promising process. Catalysts have been proposed to reduce the potential necessary for the reaction to occur, among which single-atom alloys (SAAs) are particularly promising. Here, we employ density functional theory calculations and the computational electrode model to predict whether silver-based SAAs have the potential to be effective electrocatalysts to convert CO2 into C1 products. We take into account surface defects by using the Ag(211) surface as a model. We also verify whether the proposed materials are prone to OH poisoning or enhance the competing hydrogen evolution reaction. Our calculations predict that these materials show weak mixing between the host and the dopant, characterized by a sharp peak in the density of states near the Fermi energy, except when copper (also a coinage metal) is used as the dopant. This affects the adsorption energy of the different intermediate molecules, yielding different reaction profiles for each substrate. As non-doped silver, copper-doped SAA tends to spontaneously desorb carbon monoxide (CO) instead of proceeding with its reduction. Other elements of the fourth period (Fe, Co, and Ni) tend to bind to the CO molecule but do not favor more reduced products. These metals also tend to enhance the hydrogen evolution reaction. On the contrary, we show that the Ir and Rh dopants have significant potential as electrocatalysts, which favors the reduction of CO over its desorption while also suppressing the hydrogen evolution reaction at potentials lower than those required by copper. They have also been shown to not be prone to poisoning by OH radicals., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

Efficient surface passivation and toxic lead (Pb) are known obstacles to the photovoltaic application of perovskite-based solar cells. A possible solution for these problems is to use thin-films of two-dimensional (2D) perovskite-based materials and the replacement of Pb with alternative divalent cations (B); however, our atomistic understanding of the differences between (3D) three-dimensional and 2D perovskite-based materials is far from satisfactory. Herein, we report a systematic theoretical investigation based on ab initio density functional theory (DFT) calculations for both 3D MABX 3 and the Ruddlesden-Popper 2D (BA) 2 (MA)B 2 X 7 (B = Ge, Sn, Pb, and X = Cl, Br, I) compounds to investigate the differences (contrasts) in selected physical-chemical properties, i.e. , structural parameters, energetic stability, electronic, and optical properties. We found an increased cation/anion charge separation because of the presence of organic spacers, which results in stronger Coulomb interactions in the inorganic framework, and hence, it enhances the cohesive energy (stability) within the inorganic layer. The inorganic layer constitutes the optically active region that contributes to the superior performance of perovskite-based solar cells. We quantified this effect by comparing the average electronic charges at the X sites in both 2D and 3D perovskites. This comparison is then correlated with variations in BX 6 -octahedron volumes, resulting in a monotonic relation. Moreover, the electronic structure characterization demonstrates that Ge-based systems present weakly sensitive band gaps to dimensionality due to a compensatory effect between Jahn-Teller distortions and quantum confinement. Lead-free GeI-, SnBr-, and SnI-based perovskites have DFT band gaps closer to the optimal value used in photovoltaic applications. Finally, as expected, the 2D systems absorption coefficients show pronounced anisotropy.

Chiral organic-inorganic perovskites exhibit unique physicochemical properties driven by the symmetry of monovalent organic cations. However, an atomistic understanding of how chiral cations transfer their chirality to the inorganic framework and the role played by van der Waals (vdW) interactions in this process is still incomplete. In this work, we report a theoretical investigation, based on density functional theory calculations within the Perdew-Burke-Ernzerhof (PBE) formulation for the exchange-correlation functional, into the role of the vdW interactions in the chirality transfer process. For that, we selected several vdW corrections, namely, Grimme (D2, D3, D3(BJ)), Tkatchenko-Scheffler (TS, TS+SCS, TS+HSI), density-dependent energy correction (dDsC), and many-body scattering (MBD) energy method correction. For the chiral perovskite systems, we selected a set of chiral organic-inorganic perovskites with several dimensions, namely, from zero-dimensional to three-dimensional, each having enantiomers with R and S configurations. Based on a statistical treatment of the relative errors of all lattice parameters with respect to experimental data, we found that D3, D3(BJ), TS, TS+SCS, TS+HSI, and MBD vdW are the most accurate corrections to describe the equilibrium structural properties of chiral perovskites using the PBE method. We identify chirality-induced sequential asymmetries of distorted octahedrons and propose angular descriptors to quantify them, where the orientations of these distortions depend on the R or S nature of the chiral cations. Furthermore, we demonstrate the importance of accurate vdW interactions in precisely describing these asymmetric distortions. By means of binding energies and charge-transfer analysis, we show that the impact of vdW corrections on the charge distribution leads to a subtle strengthening of hydrogen bonds between chiral cations and inorganic octahedra, resulting in an increase in the binding energy. Finally, we identified that the Rashba-Dresselhaus effect in two-dimensionality is refined by vdW interactions.

There has been a growing recognition of the need for diversity and inclusion in scientific fields. This trend is reflected in the Journal of Chemical Information and Modeling (JCIM), where there has been a gradual increase in the number of papers that embrace this diversity. In this viewpoint, we analyze the evolution of the profile of papers published in JCIM from 1996 to 2022 addressing three diversity criteria, namely interdisciplinarity, geographic and gender distributions, and their impact on citation patterns. We used natural language processing tools for the classification of main areas and gender, as well as metadata, to analyze a total of 7384 articles published in the categories of research articles, reviews, and brief reports. Our analyses reveal that the relative number of articles and citation patterns are similar across the main areas within the scope of JCIM, and international collaboration and publications encompassing two to three research areas attract more citations. The percentage of female authors has increased from 1996 (less than 20%) to 2022 (more than 32%), indicating a positive trend toward gender diversity in almost all geographic regions, although the percentage of publications by single female authors remains lower than 20%. Most JCIM citations come from Europe and the Americas, with a tendency for JCIM papers to cite articles from the same continent. Furthermore, there is a correlation between the gender of the authors, as JCIM manuscripts authored by females are more likely to be cited by other JCIM manuscripts authored by females.

Poorly selective mixed-metal cluster synthesis and separation yield reaction solutions of inseparable intermetalloid cluster mixtures, which are often discarded. High-resolution mass spectrometry, however, can provide precise compositional data of such product mixtures. Structure assignments can be achieved by advanced computational screening and consideration of the complete structural space. Here, we experimentally verify structure and composition of a whole cluster ensemble by combining a set of spectroscopic techniques. Our study case are the very similar nickel/gallium clusters of M 12 , M 13 and M 14 core composition Ni 6+x Ga 6+y (x + y ≤ 2). The rationalization of structure, bonding and reactivity is built upon the organometallic superatom cluster [Ni 6 Ga 6 ](Cp*) 6  = [Ga 6 ](NiCp*) 6 (1; Cp* = C 5 Me 5 ). The structural conclusions are validated by reactivity tests using carbon monoxide, which selectively binds to Ni sites, whereas (triisopropylsilyl)acetylene selectively binds to Ga sites., (© 2024. The Author(s).)

Gold nanoclusters have attracted significant attention due to their unique physical-chemical properties, which can be tuned by alloying with elements such as Cu, Pd, Ag, and Pt to design materials for various applications. Although Au-nanoalloys have promising applications, our atomistic understanding of the descriptors that drive their stability is far from satisfactory. To address this problem, we considered 55-atom model nanoalloys that have been synthesized by experimental techniques. Here, we combined data mining techniques for creating a large sample of representative configurations, density functional theory for performing total energy optimizations, and Spearman correlation analyses to identify the most important descriptors. Among our results, we have identified trends in core-shell formation in the AuCu and AuPd systems and an onion-like design in the AuAg system, characterized by the aggregation of gold atoms on nanocluster surfaces. These features are explained by Au's surface energy, packing efficiency, and charge transfer mechanisms, which are enhanced by the alloys' preference for adopting the structure of the alloying metal rather than the low-symmetry one presented by Au55. These generalizations provide insights into the interplay between electronic and structural properties in gold nanoalloys, contributing to the understanding of their stabilization mechanisms and potential applications in various fields., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

Electroreduction of CO 2 to C 2 products such as ethanol is motivated by its potential application to satisfy global energy demand in a more sustainable and renewable way. Cooper-based catalysts have exhibited highlighted performance in obtaining C 2 products, but large overpotentials and poor selectivity are still challenging. Herein, we employed density functional theory calculations and the computational hydrogen electrode model to study the impact of CuZn alloys on the mechanism and selectivity of CO 2 and CO electroreduction to C 2 products. On both clusters, the preferred pathway to ethanol and ethylene shares a common intermediate: CH 2 CHO*. On Cu 55 , ethanol formation would occur at lower electrode potential than the formation of ethylene, which agrees with experimental studies. Since Cu 42 Zn 13 increases the Gibbs free energy change between CH 2 CHO* and adsorbed acetaldehyde, the alloy exhibited lower selectivity toward ethanol than Cu 55 cluster. The role of Zn is mainly related to the stronger adsorption of the intermediates on Cu 42 Zn 13 than in the Cu 55 group. Our results suggested that the d states of Zn are involved in the adsorption of intermediates, strengthening the interaction.

Silicon (Si) fertilization is widely recognized to improve the development of crops, especially in tropical soils and cultivation under dryland management. Herein, our working hypothesis was that Si stoichiometry favors the efficient use of carbon (C), nitrogen (N), and phosphorus (P) in sugarcane plants. Therefore, a field experiment was carried out using a 3 × 3 factorial scheme consisting of three cultivars (RB92579, RB021754 and RB036066) and three forms of Si application (control without Si; sodium silicate spray at 40 mmol L -1 in soil during planting; sodium silicate spray at 40 mmol L -1 on leaves at 75 days after emergence). All Si fertilizations altered the elemental C and P stoichiometry and sugarcane yield, but silicon-induced responses varied depending on sugarcane cultivar and application method. The most prominent impacts were found in the leaf Si-sprayed RB92579 cultivar, with a significant increase of 7.0% (11 Mg ha -1 ) in stalk yield, 9.0% (12 Mg ha -1 ) in total recoverable sugar, and 20% (4 Mg ha -1 ) in sugar yield compared to the Si-without control. In conclusion, our findings clearly show that silicon soil and foliar fertilization alter C:N:P stoichiometry by enhancing the efficiency of carbon and phosphorus utilization, leading to improved sugarcane production and industrial quality., (© 2023. Springer Nature Limited.)

Purpose: To present the long-term results of intraoperative radiation therapy (IORT) for early breast cancer using a nondedicated linear accelerator., Methods and Materials: The eligibility criteria were biopsy-proven invasive carcinoma, age ≥40 years, tumor size ≤3 cm, and N0M0. We excluded multifocal lesions and sentinel lymph node involvement. All patients had previously undergone breast magnetic resonance imaging. Breast-conserving surgery with margins and sentinel lymph node evaluation using frozen sections were performed in all cases. If there were no margins or involved sentinel lymph nodes, the patient was transferred from the operative suite to the linear accelerator room, where IORT was delivered (21 Gy)., Results: A total of 209 patients who were followed up for ≥1.5 years from 2004 to 2019 were included. The median age was 60.3 years (range, 40-88.6), and the mean pT was 1.3 cm (range, 0.2-4). There were 90.5% pN0 cases (7.2% of micrometastases and 1.9% of macrometastases). Ninety-seven percent of the cases were margin free. The rate of lymphovascular invasion was 10.6%. Twelve patients were negative for hormonal receptors, and 28 patients were HER2 positive. The median Ki-67 index was 29% (range, 0.1-85). Intrinsic subtype stratification was as follows: luminal A, 62.7% (n = 131); luminal B, 19.1% (n = 40); HER2 enriched 13.4% (n = 28); and triple negative, 4.8% (n = 10). Within the median follow-up of 145 months (range, 12.8-187.1), the 5-year, 10-year, and 15-year overall survival rates were 98%, 94.7%, and 88%, respectively. The 5-year, 10-year, and 15-year disease-free rates were 96.3%, 90%, and 75.6%, respectively. The 15-year local recurrence-free rate was 76%. Fifteen local recurrences (7.2%) occurred throughout the follow-up period. The mean time to local recurrence was 145 months (range, 12.8-187.1). As a first event, 3 cases of lymph node recurrence, 3 cases of distant metastasis, and 2 cancer-related deaths were recorded. Tumor size >1 cm, grade III, and lymphovascular invasion were identified as risk factors., Conclusions: Despite approximately 7% of recurrences, we may infer that IORT may still be a reasonable option for selected cases. However, these patients require a longer follow-up as recurrences may occur after 10 years., (© 2023 The Author(s).)

Several chemical reactions with commercial and environmental importance can benefit from the development of more active or selective heterogeneous catalysts. Particularly, those catalyzed by metallic surfaces are usually impacted by the presence of defects such as kinks and dopants. Here, we employed density functional theory calculations within van der Waals correction to investigate the effects of single-atom Rh-dopants in the adsorption properties of OH and CO on stepped Ag(211) surfaces. From our calculations and analyses, we found that the dopant is more energetically stable when replacing more coordinated (and less exposed to the vacuum) sites of the surface. However, in the presence of both molecules, this trend is inverted, and the dopant is more stable in the least coordinated site (step). While OH presents high adsorption energies on both doped and non-doped silver surfaces, CO binds weakly to the noble metal, and strongly on doped sites. The results are relevant for understanding single-atom catalysts on noble-metal surfaces, where the difference in selectivity and activity between the host metal and dopants is exploited. The charge redistribution caused by the dopant, and the appearance of a sharp peak in the density of states of the surface are used to rationalize the results and provide insights into the interactions involved in the adsorption of both molecules.

Background: Boron (B) and silicon (Si) are fundamental for brassica nutrition, and in some cases, they have potential as an insecticide. Plutella xylostella (L.) (Lepidoptera: Plutellidae), one of the most economically important agricultural pests, is difficult to control due to the resistance to insecticides and the absence of alternative control methods., Results: Cauliflower leaves sprayed with Si and B showed a higher concentration of the beneficial element and micronutrient, respectively. When evaluating the firmness of the cauliflower leaves, it was found that the plants with leaf sprayings of Si and B did not differ statistically from each other. However, they showed an increase in firmness, in relation to the plants of the control treatment. Leaf spraying of Si and B on cauliflower did not influence the number of eggs/female. The attractiveness index showed that both Si and B applications stimulated the presence of second instar larvae, being more stimulating in relation to the control treatment. However, the use of Si and B in isolation showed a positive result, since it caused high mortality in diamondback moth larvae compared to the control treatment., Conclusion: The application of both foliar fertilizers positively affects the attractiveness index of the larvae, being attractive; however, both Si and B caused high mortality (~80%). The results showed that Si and B have the potential to control P. xylostella and serve as a basis for alternative pest management in brassica crops. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

Nanoclusters are remarkably promising for the capture and activation of small molecules for fuel production or as precursors for other chemicals of high commercial value. Since this process occurs under a wide variety of experimental conditions, an improved atomistic understanding of the stability and phase transitions of these systems will be key to the development of successful technological applications. In this work, we proposed a theoretical framework to explore the potential energy surface and configuration space of nanoclusters to map the most important morphologies presented by those systems and the phase transitions between them. A fully automated process was developed, which combines global optimization techniques, classical molecular dynamics, and unsupervised machine learning algorithms. To showcase these capabilities of the approach, we explored the example of copper nanoclusters (Cu n ) where n = 13, 38, 55, 75, 98, 102, and 147. We not only reported a graphical potential energy surface for each size, but also explored the topology of the configuration space via structural and thermodynamic analyses. The effect of size on the potential energy surface and the critical temperature for solid-liquid phase transitions were also reported, highlighting the impact of magic numbers on those quantities.

This research aimed to study the effects of the nanosilica supply on Si absorption and the physiological and nutritional aspects of beet plants with N and P deficiencies cultivated in a nutrient solution. Two experiments were performed with treatments arranged in a 2 × 2 factorial scheme in randomized blocks with five replications. The first experiment was carried out on plants under a N deficiency and complete (complete solution with all nutrients), combined with the absence of Si (0 mmol L -1 ) and the presence of Si (2.0 mmol L -1 ). In the other experiment, the plants were cultivated in a nutrient solution with a P deficiency and complete, combined with the absence (0 mmol L -1 ) and the presence of Si (2.0 mmol L -1 ). The beet crop was sensitive to the N and P deficiencies because they sustained important physiological damage. However, using nanosilica via fertigation could reverse the damage. Using nanotechnology from nanosilica constituted a sustainable strategy to mitigate the damage due to a deficiency in the beet crop of the two most limiting nutrients by optimizing the physiological processes, nutritional efficiency, and growth of the plants without environmental risks. The future perspective is the feasibility of nanotechnology for food security.

Ionic liquids have attracted the attention of researchers as possible electrolytes for electrochemical energy storage devices. However, their properties, such as the electrochemical stability window (ESW), ionic conductivity, and diffusivity, are influenced both by the chemical structures of cations and anions and by their combinations. Most studies in the literature focus on the understanding of common ionic liquids, and little effort has been made to find ways to improve our atomistic understanding of those systems. The goal of this paper is to explore the structural characteristics of cations and anions that form ionic liquids that can expand the HOMO/LUMO gap, a property directly linked to the ESW of the electrolyte. For that, we design a framework for randomly generating new ions by combining their fragments. Within this framework, we generate about 10 4 cations and 10 4 anions and fully optimize their structures using density functional theory. Our calculations show that aromatic cations are less stable ionic liquids than aliphatic ones, an expected result if chemical rationale is used. More importantly, we can improve the gap by adding electron-donating and electron-withdrawing functional groups to the cations and anions, respectively. The increase can be about 2 V, depending on the case. This improvement is reflected in a wider ESW.

Background: Patients with brain metastases (BM) live longer due to improved diagnosis and oncologic treatments. The association of volumetric modulated arc therapy (VMAT) and image-guided radiation therapy (IGRT) with brain radiosurgery (SRS) allows complex dose distributions and faster treatment delivery to multiple lesions., Materials and Methods: This study is a retrospective analysis of SRS for brain metastasis using VMAT. The primary endpoints were local disease-free survival (LDFS) and overall survival (OS). The secondary outcomes were intracranial disease-free survival (IDFS) and meningeal disease-free survival (MDFS)., Results: The average number of treated lesions was 5.79 (range: 2-20) per treatment in a total of 113 patients. The mean prescribed dose was 18 Gy (range: 12-24 Gy). The median LDFS was 46 months. The LDFS in 6, 12, and 24 months was for 86%, 79%, and 63%, respectively. Moreover, brain progression occurred in 50 patients. The median overall survival was 47 months. The OS in 75%, 69%, and 61% patients was 6, 12, and 24 months, respectively. IDFS was 6 and 24 months in 35% and 14% patients, respectively. The mean MDFS was 62 months; it was 6 and 24 months for 87% and 83% of patients. Acute severe toxicity was relatively rare. During follow-up, the rates of radionecrosis and neurocognitive impairment were low (10%)., Conclusion: The use of VMAT-SRS for multiple BM was feasible, effective, and associated with low treatment-related toxicity rates. Thus, treatment with VMAT is a safe technique to plan to achieve local control without toxicity., Competing Interests: Conflict of interest None declared., (© 2022 Greater Poland Cancer Centre.)

Machine learning as a tool for chemical space exploration broadens horizons to work with known and unknown molecules. At its core lies molecular representation, an essential key to improve learning about structure-property relationships. Recently, contrastive frameworks have been showing impressive results for representation learning in diverse domains. Therefore, this paper proposes a contrastive framework that embraces multimodal molecular data. Specifically, our approach jointly trains a graph encoder and an encoder for the simplified molecular-input line-entry system (SMILES) string to perform the contrastive learning objective. Since SMILES is the basis of our method, i.e., we built the molecular graph from the SMILES, we call our framework as SMILES Contrastive Learning (SMICLR). When stacking a nonlinear regressor on the SMICLR's pretrained encoder and fine-tuning the entire model, we reduced the prediction error by, on average, 44% and 25% for the energetic and electronic properties of the QM9 data set, respectively, over the supervised baseline. We further improved our framework's performance when applying data augmentations in each molecular-input representation. Moreover, SMICLR demonstrated competitive representation learning results in an unsupervised setting.

Here, we report a computational investigation on the role of the most common van der Waals (vdW) corrections (D2, D3, D3(BJ), TS, TS+SCS, TS+HI, and dDsC) employed in density functional theory (DFT) calculations within local and semilocal exchange-correlation functionals to improve the description of the interaction between molecular species and solid surfaces. For this, we selected several molecular model systems, namely, the adsorption of small molecules (CH 3 , CH 4 , CO, CO 2 , H 2 O, and OH) on the close-packed Cu(111) surface, which bind via chemisorption or physisorption mechanisms. As expected, we found that the addition of the vdW corrections enhances the energetic stability of the Cu bulk in the face-centered cubic structure, which contributes to increasing the magnitude of the mechanical properties (elastic constants, bulk, Young, and shear modulus). Except for the TS+SCS correction, all vdW corrections substantially increase the surface energy, while the work function changes by about 0.05 eV (largest change). However, we found substantial differences among the vdW corrections when comparing its effects on interlayer spacing relaxations. Based on bulk and surface results, we selected only the D3 and dDsC vdW corrections for the study of the adsorption properties of the selected molecules on the Cu(111) surface. Overall, the addition of these vdW corrections has a greater effect on weakly interacting systems (CH 4 , CO 2 , H 2 O), while the chemisorption systems (CH 3 , CO, OH) are less affected.

Multiple aspects of the physiological and nutritional mechanisms involved with silicon (Si) absorption by quinoa plants remain poorly investigated, as well as the best way of supplying this element to crops. Thus, this study aimed at evaluating whether the application of Si increases its uptake by quinoa plants and consequently the use efficiency of N and P, as well as the levels of phenolic compounds in the leaves, crop productivity and the biofortification of grains. For this purpose, the concentration of 3 mmol L -1 of Si was tested, according to the following procedures: foliar application (F), root application in the nutrient solution (R), combined Si application via nutrient solution and foliar spraying (F + R), and no Si application (0). The provision of Si through the leaves and roots promoted the highest uptake of the element by the plant, which resulted in an increased use efficiency of N and P. Consequently, such a higher uptake favored the productivity of grains. The optimal adoption of the application of Si through leaves and roots promoted the highest Si concentration and ascorbic acid content in quinoa grains., (© 2022. The Author(s).)

Understanding the dynamics of charge transfer at vertical heterostructures of transition metal dichalcogenide monolayers is fundamentally important for future technological applications, given the unique feature of van der Waals interactions at the interface. Here, we employ time-dependent density functional theory formalism combined with molecular dynamics to investigate photoexcited electrons and holes in the type-I MoS 2 /PtSe 2 van der Waals heterobilayer. While type-I junctions have been traditionally viewed as being ineffective in photocarrier separation, we show that here a different mechanism from type-II is at play, which effectively separates photoelectrons from photoholes. The key is the phonon bottleneck, arising from the characteristically different dynamic band alignments in the valence and conduction bands, respectively, which only affects the transfer of holes but not electrons. The disparity between electron and hole transfer rates offers a new direction for effective control of charge separation at interfaces.

The Ni 5 Ga 3 alloy supported on ZrO 2 is a promising catalyst for the reduction of CO 2 due to its higher selectivity to methanol at ambient pressure, e.g., activity comparable to industrial catalysts. However, our atomistic understanding of the role of the cooperative effects induced by the Ni 5 Ga 3 alloy formation and its Ni 5 Ga 3 /ZrO 2 interface in the CO 2 reduction is still far from satisfactory. In this work, we tackle these questions by employing density functional theory calculations to investigate the adsorption properties of key CO 2 reduction intermediates (CO 2 , H 2 , cis-COOH, trans-COOH, HCOO, CO, HCO, and COH) on Ni 8 , Ga 8 , Ni 5 Ga 3 , (ZrO 2 ) 16 , and Ni 5 Ga 3 /(ZrO 2 ) 16 . We found that Ni containing clusters tended to assume wetting configurations on the (ZrO 2 ) 16 cluster, while the presence of Ga atoms weakens the adsorption energies on the oxide surface. We also observed that CO 2 was better activated on the metal-oxide interfaces and on the oxide surface, where it was able to form CO 3 -like structures. Meanwhile, H 2 activation was only observed on Ni sites, which indicates the importance of distinct adsorption sites that can favor different CO 2 reduction steps. Moreover, the formation of the metal-oxide interface showed to be beneficial for the adsorption of COOH isomers and unfavorable for the adsorption of HCOO.

Two-dimensional (2D) chalcogenides have attracted great interest from the scientific community due to their intrinsic physical-chemical properties, which are suitable for several technological applications. However, most of the reported studies focused on particular compounds and composition, e.g., MoS 2 , MoSe 2 , WS 2 , and WSe 2 . Thus, there is an increased interest to extend our knowledge on 2D chalcogenides. Here, we report a density functional theory (DFT) screening of 2D coinage-metal chalcogenides ( MQ x ), where M = Cu, Ag, Q = S, Se, Te, x = 0.5, 1.0, 1.5, 2.0, with the aim to improve our atomistic understanding of the physical-chemical properties as a function of cation ( M ), anion ( Q ), and composition ( x ). Based on 258 DFT calculations, we selected a set of 22 stable MQ x monolayers based on phonons analyses, where we identified 9 semiconductors (7 AgQ x and 2 CuQ x ), with band gaps from 0.07 eV up to 1.67 eV, while the remaining systems have a metallic character. Using all 258 systems, we found a logarithmic correlation between the average weighted bond lengths and effective coordination number of cations and anions. As expected, the monolayer cohesive energies increase with the radius of the Q species (i.e., from S to Te). Furthermore, an increase in the anion size diminishes the work function for nearly all MQ x monolayers, which can be explained by the nature of the electronic states at the valence band maximum., (© 2022 IOP Publishing Ltd.)

We report improvement in the perovskite solar cell efficiency and stability after passivation with an organic molecule decorated with two anilinium cations. We compare this salt with its neutral analog and found that the change in the electron density distribution upon protonation and the presence of the halide anion are key to explaining the better passivation ability of the salt. In addition, we show that the counteranion has a significant impact on the performance of the device., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

We report a theoretical investigation of the adsorption and activation properties of CO 2 on eight-atom 3d, 4d, and 5d transition-metal (TM) clusters based on density functional theory calculations. From our results and analyses, in the lowest energy configurations, CO 2 binds via a chemisorption mechanism on Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt (adsorption energy from -0.49 eV on Pt up to -1.40 eV on Os), where CO 2 breaks its linearity and adopts an angular configuration due to the charge transfer from the clusters toward the C atom in the adsorbed CO 2 . In contrast, it binds via physisorption on Cu, Ag, and Au and maintains its linearity due to a negligible charge transfer toward CO 2 and has a small adsorption energy (from -0.17 eV on Cu up to -0.18 eV on Ag). There is an energetic preference for twofold bridge TM sites, which favors binding of C with two TM atoms, which enhances the charge transfer ten times than on the top TM sites (onefold). We identified that the strength of the CO 2 -TM 8 interaction increases when the energy values of the highest occupied molecular orbital (HOMO) of the TM 8 are closer to the energy values of the lowest unoccupied molecular orbital of CO 2 , which contributes to maximize the charge transfer toward the molecule. Beyond the energy position of the HOMO states, the delocalization of 5d orbitals plays an important role in the adsorption strength in TM, especially for the iron group, e.g., the adsorption energies are -1.08 eV (Fe, 3d), -1.19 eV (Ru, 4d), and -1.40 eV (Os, 5d).

Some of the most common applications of machine learning (ML) algorithms dealing with small molecules usually fall within two distinct domains, namely, the prediction of molecular properties and the design of novel molecules with some desirable property. Here we unite these applications under a single molecular representation and ML algorithm by modifying the grammar variational autoencoder (GVAE) model with the incorporation of property information into its training procedure, thus creating a supervised GVAE (SGVAE). Results indicate that the biased latent space generated by this approach can successfully be used to predict the molecular properties of the input molecules, produce novel and unique molecules with some desired property and also estimate the properties of random sampled molecules. We illustrate these possibilities by sampling novel molecules from the latent space with specific values of the lowest unoccupied molecular orbital (LUMO) energy after training the model using the QM9 data set. Furthermore, the trained model is also used to predict the properties of a hold-out set and the resulting mean absolute error (MAE) shows values close to chemical accuracy for the dipole moment and atomization energies, even outperforming ML models designed to exclusive predict molecular properties using the SMILES as molecular representation. Therefore, these results show that the proposed approach is a viable way to provide generative ML models with molecular property information in a way that the generation of novel molecules is likely to achieve better results, with the benefit that these new molecules can also have their molecular properties accurately predicted.

The analysis via density functional theory was employed to understand high photocatalytic activity found on the Au-Ag high-noble alloys catalysts supported on rutile TiO 2 during the oxygen evolution of water oxidation reaction (OER). It was indicated that the most thermodynamically stable location of the Au-Ag bimetal-support interface is the bridging row oxygen vacancy site. On the active region of the Au-Ag catalyst, the Au site is the most active for OER catalyzing the reaction with an overpotential of 0.60 V. Whereas the photocatalytic activity of other active sites follows the trend of Au > Ag > Ti. This finding evident from the projected density of states revealed the formation of the trap state that reduces the band gap of the catalyst promoting activity. In addition, the Bader charge analysis revealed the electron relocation from Ag to Au to be the reason behind the activity of the bimetallic that exceeds its monometallic counterparts., (© 2022. The Author(s).)

Cowpea [ Vigna unguiculata (L.) Walp] is cultivated in tropical and subtropical regions worldwide, but its production is usually limited by boron (B) deficiency, which can be mitigated by applying B via foliar spraying. In plants with nutrient mobility, the residual effect of foliar fertilization increases, which might improve its efficiency. An experiment was carried out to evaluate the concentration and mobility of the B isotopic tracer ( 10 B) in different organs of cowpea plants, after the application of this micronutrient in the growing media and also to leaves. Treatments were designed based on B fertilization as follows: without B in the growth media, with 10 B applied via foliar spraying ( 10 B-L), with B in the growth media (substrate) and 10 B via foliar spraying ( 10 B-L + B-S), and with 10 B in the growth media (substrate) without foliar spraying ( 10 B-S), and a control without fertilization. A redistribution of 10 B was observed in new leaves when the element was supplied via foliar spraying, resulting in greater leaf area, dry mass and dry matter production of aerial parts, and also the whole plant. 10 Boron was redistributed when applied via foliar spraying in cowpea plants, regardless of the plant's nutritional status, which in turn might increase internal B cycling., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Silva, Prado, Abreu-Junior, Silva, Silva Júnior and Silva.)

Background: This study aims to assess the clinical outcomes of patients with spine metastases who underwent stereotactic ablative radiation therapy (SABR) as part of their treatment. SABR has arisen as a contemporary treatment option for spinal metastasis patients with good prognoses., Materials and Methods: Between November 2010 and September 2018, Spinal SABR was performed in patients with metastatic disease in different settings: radical (SABR only), postoperative (after decompression and/or fixation surgery), and reirradiation. Local control (LC), pain control, overall survival (OS) and toxicities were reported., Results: Eighty-five patients (corresponding to 96 treatments) with spine metastases were included. The median age was 59 years (range, 23-91). In most SA BR (82.3%, n = 79) was performed as the first local spine treatment, while in 12 settings (12.5%), fixation and/or decompression surgery was performed prior to SABR. Two-year overall survival rate was 74.1%, and median survival was 19 months. The LC rate at 2 years was 72.3%. With regard to pain control, among 67 patients presenting with pain before SA BR, 83.3% had a complete response, 12.1% had a partial response, and 4.6% had progression. Vertebral compression fractures occurred in 10 patients (11.7%), of which 5 cases occurred in the reirradiation setting. Radiculopathy and myelopathy were not observed. No grade III or IV toxicities were seen., Conclusion: This is the first study presenting a Brazilian experience with spinal SA BR, and the results confirm its feasibility and safety. SABR was shown to produce good local and pain control rates with low rates of adverse events., Competing Interests: Conflict of interest None declared., (© 2021 Greater Poland Cancer Centre.)

Most machine learning applications in quantum-chemistry (QC) data sets rely on a single statistical error parameter such as the mean square error (MSE) to evaluate their performance. However, this approach has limitations or can even yield incorrect interpretations. Here, we report a systematic investigation of the two components of the MSE, i.e., the bias and variance, using the QM9 data set. To this end, we experiment with three descriptors, namely (i) symmetry functions (SF, with two-body and three-body functions), (ii) many-body tensor representation (MBTR, with two- and three-body terms), and (iii) smooth overlap of atomic positions (SOAP), to evaluate the prediction process's performance using different numbers of molecules in training samples and the effect of bias and variance on the final MSE. Overall, low sample sizes are related to higher MSE. Moreover, the bias component strongly influences the larger MSEs. Furthermore, there is little agreement among molecules with higher errors (outliers) across different descriptors. However, there is a high prevalence among the outliers intersection set and the convex hull volume of geometric coordinates (VCH). According to the obtained results with the distribution of MSE (and its components bias and variance) and the appearance of outliers, it is suggested to use ensembles of models with a low bias to minimize the MSE, more specifically when using a small number of molecules in the training set.

There is an intense race by the scientific community to identify materials with potential applications for the conversion of carbon dioxide (CO 2 ) into new products. To extend the range of possibilities and explore new effects, in this work, we employ density functional theory calculations to investigate the presence of edge effects in the adsorption and activation of CO 2 on pristine and Fe-decorated (WS 2 ) 16 nanoflakes. We found that Fe has an energetic preference for hollow sites on pristine nanoflakes, binding with at least two two-fold edge S atoms and one or two three-fold core S atoms. Fe adsorption on the bridge sites occurs only at the edges, which is accompanied by the breaking of W-S bonds in most cases (higher energy configurations). CO 2 activates on (WS 2 ) 16 with an OCO angle of about 129° only at higher energy configurations, while CO 2 binds via a physisorption mechanism, linear structure, in the lowest energy configuration. For CO 2 on Fe/(WS 2 ) 16 , the activation occurs at lower energies only by the direct interaction of CO 2 with Fe sites located near to the nanoflake edges, which clearly indicates the enhancement of the catalytic activity of (WS 2 ) 16 nanoflakes by Fe decoration. Thus, our study indicates that decorating WS 2 nanoflakes with TM atoms could be an interesting strategy to explore alternative catalysts based on two-dimensional materials.

The adsorption of alcohols on transition-metal (TM) substrates has received the attention of many researchers due to the applications of alcohols in several technological fields. However, our atomic-level understanding is still far from satisfactory, in particular for the interaction of alcohols with finite-size TM clusters, where new effects can arise due to the presence of quantum-size effects. In this work, we report a theoretical investigation of the adsorption properties of methanol, ethanol, and ethylene glycol on 12 different 3d, 4d, and 5d TM 15 clusters based on density functional theory calculations within the semi-empirical D3 van der Waals corrections. From the correlation analysis of all the lowest- and high-energy configurations, we identified the adsorption modes of methanol, ethanol, and ethylene glycol on the TM 15 clusters, in which the OH group binds to the cationic TM sites via the O-TM and H-TM interactions. Due to the relatively weak alcohol-TM 15 interaction, the changes induced on the TM 15 clusters are small, except for Au 15 and Ru 15 , where the bare cluster changes its structure to a nearby minimum in the potential energy surface. The adsorption energy for the alcohol/TM 15 systems is correlated to the combination of several parameters, in which the main contribution is connected with the O-TM interaction and the HOTM angles. Furthermore, the TM electronegativity is an important descriptor for the methanol and ethanol adsorption energies, while charge transfer is important for ethylene glycol.

Here, we report density functional theory calculations combined with the k -means clustering algorithm and the Spearman rank correlation analysis to investigate the stability mechanisms of eight-atom binary metal AB clusters, where A and B are Fe, Co, Ni, Cu, Ga, Al, and Zn (7 unary and 21 binary clusters). Based on the excess energy analysis, the six most stable binary clusters are NiAl, NiGa, CoAl, FeNi, NiZn, and FeAl, and except for FeNi, their highest energetic stabilities can be explained by the hybridization of the d- and sp -states, which is maximized at the 50% composition, i.e., A 4 B 4 . Based on the Spearman correlation analysis, the energetic stability of the binary clusters increases with an increase in the highest occupied molecule orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy separation, which can be considered as a global descriptor. Furthermore, reducing the total magnetic moment values increases the stability for binary clusters without the Fe, Co, and Ni species, while the binary FeB, CoB, and NiB clusters increase their energetic stability with a decrease in the cluster radius, respectively, i.e., an energetic preference for compact structures.

Copper-exchanged zeolites have demonstrated high selectivity in methane-to-methanol conversion carried out on copper-oxo centers. Nevertheless, the reaction can only occur if the methane molecules reach the active site while the methanol molecules must leave the material without high energetic cost for the migration. In this context, we have used force field-based molecular dynamics simulations with the potential of mean force method to estimate the energy barrier in cage to cage diffusion of methane and methanol molecules in the chabazite framework type zeolite. The results show considerably higher energy barrier for methanol diffusion. The steric effect of the active site and the electrostatic environment favors the CH 3 OH diffusion toward nonactive cages where it tends to accumulate due to the strong interactions with the zeolite. The same behavior is observed in the water molecules distribution, which emphasizes the control of the electrostatic potential over the polar molecules migration. For high concentration of polar molecules, the electrostatic effect is shielded and the driving force is reduced for CH 3 OH diffusion. The results show that if the electrostatic environment can be controlled, the product migration may be facilitated, which can improve the catalytic process.

Our atomistic understanding of the physical-chemical parameters that drives the changes in the relative stability of clusters induced by adsorbed molecules is far from satisfactory. In this work, we employed density functional theory calculations to address this problem using CO adsorption on 13-atom transition-metal clusters, TM 13 , namely, n CO/TM 13 , where TM = Ru, Rh, Pd, and Ag, and n = 1-6. Unexpectedly, changes in the relative stability take place for all systems at a lower coverage, namely, at n = 3 (Ru 13 ), 4 (Rh 13 , Ag 13 ), and 2 (Pd 13 ). To address the effects that lead to changes in the stability, we proposed an energy decomposition scheme for the binding energy of the n CO/TM 13 systems, which yields that the change in relative stability is dominated by the interaction energy and cluster distortion energy upon adsorption, where the interaction energy is higher for high-energy unprotected clusters. Furthermore, we characterized all adsorption parameters, which helps us to complement our atomistic understanding.

Recognizably, silicon has a beneficial effect on plant growth and productivity. In this respect, it is also known that the C, N and, P stoichiometric ratios and nutrient conversion efficiency allow identifying the interactions between elements while helping to understand the role Si plays in plant growth. This study aims to investigate whether increasing Si concentrations (0, 1, 2, and 3 mmol L -1 ) supplied in the nutrient solution is uptaken by quinoa, modifies the C:N:P stoichiometry while increasing nutritional efficiency and crop productivity as well. Our results revealed that the Si supply by promoting a decline in the C levels, associated with greater uptake of N and P, especially decreased the C:N and C:P ratios, favoring the C metabolism efficiency, and modulated the N and P use efficiency for biomass accumulation. This improved nutritional performance and greater use efficiency of C directly favored quinoa productivity. The future perspective is to encourage new field studies with this species to adjust silicon fertilization management to different soils aiming at enhancing quinoa productivity on a sustainable basis.

Here, we report a theoretical investigation, based on density functional theory calculations, into the role of the occupation d-states on the adsorption properties of CH 4 , CO, H 2 and CH 3 OH on 3d 13-atom transition-metal (TM 13 ) clusters (TM = Fe, Co, Ni, Cu). Except for Cu 13 , a gradual increase in the occupation of the d-states, i.e., from Fe 13 to Ni 13 , increases the magnitude of the adsorption energy almost linearly for the H 2 /TM 13 and CO/TM 13 systems, which can be explained by the enhancement of the sp-d hybridization due to the shift of the d-states towards the highest occupied molecular orbital (HOMO). For Cu 13 , the d-states are located well below the HOMO, which reduces the sp-d hybridization, and hence, a smaller adsorption energy is obtained. However, this picture does not hold for CH 4 /TM 13 and CH 3 OH/TM 13 , where the adsorption energy has nearly the same value for all TM 13 clusters, which can be explained by electrostatic effects such as local polarization of the molecules and nearby TM atoms, and hence, the basic features of physisorption systems. Based on the electron density difference, the polarization effects are slightly larger for systems with empty d-states.

The amount of quantum chemistry (QC) data is increasing year by year due to the continuous increase of computational power and development of new algorithms. However, in most cases, our atom-level knowledge of molecular systems has been obtained by manual data analyses based on selected descriptors. In this work, we introduce a data mining framework to accelerate the extraction of insights from QC datasets, which starts with a featurization process that converts atomic features into molecular properties (AtoMF). Then, it employs correlation coefficients (Pearson, Spearman, and Kendall) to investigate the AtoMF features relationship with a target property. We applied our framework to investigate three nanocluster systems, namely, Pt n TM 55- n , Ce n Zr 15- n O 30 , and (CH n + m H)/TM 13 . We found several interesting and consistent insights using Spearman and Kendall correlation coefficients, indicating that they are suitable for our approach; however, our results indicate that the Pearson coefficient is very sensitive to outliers and should not be used. Moreover, we highlight problems that can occur during this analysis and discuss how to handle them. Finally, we make available a new Python package that implements the proposed QC data mining framework, which can be used as is or modified to include new features.

In this study, we report an ab initio screening, based on density functional theory calculations, of Pt-based transition-metal nanoalloys using physicochemical descriptors derived from the adsorption and activation of CO2 on 55-atom nanoclusters, namely, PtnTM55-n, with n = 0, 13, 42, 55, TM = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Au. From the adsorption on the unary and binary nanoclusters, at the chemisorption regime (bent CO2), we identified a linear correlation between the interaction energy and charge transfer from the nanoclusters towards CO2 and the bent CO2 angle; moreover, the interaction energy is enhanced for larger values of the molecular charge and angle. The alloying of Cu55, Ag55, and Au55 with Pt provides a path to change the CO2 adsorption from physisorption (linear, non-activated) to chemisorption (enhanced interaction energies, bent, activated), while the strong interaction energy of CO2 with Os55, Ru55, and Fe55 can be decreased by alloying with Pt using different structural configurations, i.e., the trends are similar for core-shell and segregated structures. Thus, based on our results and analyses, we can select different combinations of PtnTM55-n nanoalloys to yield the desired interaction strength and magnitude of the charge transfer towards the activated anionic CO2, which can help in the design of nanocatalysts for CO2 activation or different chemical reactions in which charge transfer plays a crucial role.

Tin-based ASnI3 perovskites have been considered excellent candidates for lead-free perovskite solar cell applications; however, our atomistic understanding of the role of the A-cations, namely, CH3NH3 (methylammonium, MA), CH3PH3 (methylphosphonium, MP) and CH(NH2)2 (formamidinium, FA), in the physical chemistry properties is far from satisfactory. For the first time, we report a density functional theory investigation of the MPSnI3 perovskite and non-perovskite phases as well as their comparison with the MASnI3 and FASnI3 phases, where we considered the role of the A-cation orientations in the structural stability of the ASnI3 phases. The orthorhombic structure is the most stable studied phase, which agrees with experimentally reported phase-transition trends. In contrast with the cation size and the weak hydrogen bonding interactions, which contribute to structural cohesion between the inorganic framework and A-cation, the dipole-dipole interactions play an important role to drive the structures to the lowest energy configurations. From our analysis, the inorganic framework dominates the optical properties, band structure, and density of states around the band edges. Broader absorption and smaller band gap energies occur for the perovskite structures compared to the low-dimensional hexagonal/pseudo-hexagonal non-perovskites.

Calcium (Ca) deficiency in cabbage plants induces oxidative damage, hampering growth and decreasing quality, however, it is hypothesized that silicon (Si) added to the nutrient solution may alleviate crop losses. Therefore, this study aims at evaluating whether silicon supplied in the nutrient solution reduces, in fact, the calcium deficiency effects on cabbage plants. In a greenhouse, cabbage plants were grown using nutrient solutions with Ca sufficiency and Ca deficiency (5 mM) without and with added silicon (2.5 mM), arranged as a 2 × 2 factorial in randomized blocks, with five replications. At 91 days after transplanting, the plants were harvested for biological evaluations. In the treatment without added Si, Ca deficiency promoted oxidative stress, low antioxidant content, decreased dry matter, and lower quality leaf. On the other hand, added Si attenuated Ca deficiency in cabbage by decreasing cell extravasation while increasing both ascorbic acid content and fresh and dry matter, providing firmer leaves due to diminished leaf water loss after harvesting. We highlighted the agronomic importance of Si added to the nutrient solution, especially in crops at risk of Ca deficiency.