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In this theoretical work, density functional theory calculations show the effect of small cobalt clusters (Con, n = 1–5) adsorbed on pristine γ‐graphyne (γ‐GY), and modify N‐doped γ‐GY monolayers (GYNs‐def). Different geometrical configurations are assessed with the adsorption energy, charge transfer, and density of states. The system with vacancy defects shows a large adsorption energy (19.96 eV) for the Co5 cluster. This behavior may be associated to the overlapping of the electronic state contributions between cobalt and carbon atoms in the valence states. This indicates that the Co5 cluster could be deposited on N‐doped γ‐GY monolayers (Con@GYNs‐def). The lowest‐energy systems are evaluated to estimate the strength of the interaction with hydrogen molecules (xH2, where x = 1–5). According to the adsorption energy values, the modified γ‐GY monolayers are allowed to be a suitable support material to capture H2 molecules via the small Con clusters. The hydrogen retention capacity for the supported cobalt atoms corresponding to the lowest‐energy configurations and larger systems are evaluated by using molecular dynamics simulations with the Born–Oppenheimer approximation. The role played by defects in the GYNs‐def monolayers is important, since the Con clusters remain attached to the vacancy with the absence of surface diffusion. This study may represent a guide to tailor novel nanostructures based on small cobalt clusters supported on graphyne monolayers modified to be applied in H2 adsorption. [ABSTRACT FROM AUTHOR]

The improvement of performance in sodium ion batteries is a subject of intense research. In this work, a first principle calculations study at the density functional level on the adsorption process of Na adatoms into Sb2S3/carbon (Sb2S3/CM) and Sb2S3/heteroatom doped‐carbon (Sb2S3/S‐CM, Sb2S3/Sb‐CM) is presented. The sulfur and antimony doped‐carbon substrates enhance the adsorption energies, charge transfer, specific capacities and the diffusion properties of Na adatoms into the Sb2S3/S‐CM and Sb2S3/Sb‐CM composite systems. The Na storage capacity trend and the open circuit voltage profile follows the trend observed in previous experimental results. This work explores perspectives through tailoring 2D carbon anodes with doping heteroatoms in the presence of adsorbed Sb2S3 for an outstanding storage capacity and cycling stability architecture. [ABSTRACT FROM AUTHOR]

Doped fullerenes are extraordinary materials with unique electronic and optical properties, which also show potential for diverse biomedical applications. Employing density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations; we studied the propensity of C36 and C35E (E=N and B) fullerenes as potential nanovehicles for certain neuroprotective drugs that are efficacious for Parkinson's disease. Baclofen, modafinil, rasagiline and rivastigmine were systematically studied to analyze whether they could be carried by small fullerenes. C36 and C35N fullerenes represent promising nanostructure candidates, due to their adsorption energy (physisorption) and favorable electrostatic interaction for the molecular transport of baclofen and rivastigmine drugs. Furthermore, in order to evaluate the effect of temperature on these interactions, ab initio molecular dynamics (AIMD) were also performed. The results from this work are expected to motivate additional investigations concerning these systems, using both theoretical and experimental approaches, in order to demonstrate their versatility as novel carbon‐based nanovehicles. [ABSTRACT FROM AUTHOR]

Pristine and boron‐doped fullerenes have been widely investigated for their possible use in medical applications, as drug delivery nanovehicles. In this study, we investigate bare and B‐doped C20, C36 and C60 fullerenes and their interaction with piribedil drug molecule, based on density functional theory (DFT). Calculations were performed using the functional PBE of general gradient approximation, empirical dispersion correction by Grimme under vacuum conditions, pentylethanoate and water media. In this article, we examine optimized geometries, binding energies, theoretical IR spectra and the plots of Molecular Electrostatic Potential, as well as HOMO and LUMO orbitals, density of states (DOS) and the quantum theory of atoms in molecules (QTAIM), in order to truly comprehend the interaction between various fullerenes and piribedil. Findings suggest that C36, C60 and C35B fullerenes might be used as drug delivery vehicles for piribedil because of their moderately high adsorption energies with piribedil. [ABSTRACT FROM AUTHOR]

Abstract Electrode materials for energy storage devices based on carbon materials have shown to be a reliable choice in supercapacitors or Li-ion batteries. The development of novel carbon materials may improve the performance of such devices and the use of eco-friendly materials from biomass waste may provide a breakthrough in the area. In this study, we give theoretical insights into the in silico design of carbon materials based on lignocellulosic molecules present in the waste residues. We performed pyrolysis-simulated calculations at the ReaxFF level with the Adler's softwood lignin model as the precursor material. Different models were implemented by randomly combining massive lignocellulosic molecules. The simulated pyrolysis of the lignocellulosic components was performed starting with a heating step from room temperature to a temperature limit of 1280 K, followed by a stabilization period. The reaction was subjected to quenching, and finally to a period of thermal equilibrium. The formed char was characterized as nanoporous carbon according to its density, radial distribution function and pore size distributions. Comparison of these results with our available experimental data revealed reasonable agreement. This may aid in the design of carbon electrodes for energy storage devices and applications in which stable and predictable properties are desirable. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The novel carbon cages are able of encapsulating metal atoms. • The presence of Sc atom enhances stability of the carbon cages. • The charge transfer mechanisms between the M atoms to the carbon cages are analysed. • Encapsulation of Sc atoms is stable according to thermal stability test. Abstract Quasi-fullerenes ( C n - q , where q stands for quasi) are novel molecules that exhibit geometries such as carbon cages with interesting electronic structure properties due to the diversity on the shape of the rings in their structure. In this work, we studied the structural stability and electronic structure properties of possible endohedral metallo quasi-fullerenes M@ C n - q (M = Sc, Ti, V, Cr; n = 42, 48 and 60). These systems have been systematically investigated using density functional theory calculations. We calculated binding energies with the zero-point energy correction to determine the stability of these new endohedral compounds. We found that the bond between Sc with the carbon cages is mostly covalent. Moreover, all metals transferred charge to the cage. The stability and reactivity were also evaluated with the following criteria: hardness (η), chemical potential (μ) and HOMO–LUMO gaps (Δ E HOMO - LUMO ). The charge distributions were studied with NBO population analysis, molecular electrostatic potential isosurfaces and electron localization functions. The cage aromaticity was evaluated in accordance to nuclear independent chemical shift methodology, and it was disclosed that the insertion of these metals increased aromaticity, showing that this property may play a crucial role in the stabilization of the endohedral species. We also studied thermal stability for the Sc@ C n - q series with Lagrangian molecular dynamics using Atom Center Density Matrix Propagation method. This work may aid to understand the possibility to determine the formation of new carbon cages with the ability to trap metal atoms. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract In this theoretical work, we present the results from Density Functional Theory (DFT) calculations on novel systems formed by graphyne-γ (GY-γ) with defects, and Nitrogen-doped graphyne (GYN) systems. Systems with vacancy defects present a widening on the band gap. We found that the electronic properties of the GYN family may be tuned, from a semiconducting to a metallic character. This may be due to the presence of Nitrogen atoms (N) in acetylenic linkages. The N-doping was shown to generate thermodynamically stable systems with different electronic properties, which can be further confirmed by ab initio Molecular Dynamics simulations. In this work, we also analyzed the chemical stability and reactivity with the following criteria: hardness, chemical potential, and electronic density. The GYN system with defects (GYN-def) presents the lowest-energy of formation and cohesion, indicating that it may correspond to the most energetically stable system. The catalytic character of the series of graphyne systems under study was tested by assessing the capability to adsorb the O 2 molecule on the graphyne substrate. It was discovered that the GYN-β and -δ systems represent models able to achieve O 2 molecular chemisorption onto the surface, due to the modified electronic structure after N-doping. We found activation barriers below 0.70 eV. This addresses that the process might occur spontaneously at rom temperature. Such graphyne systems represent potential candidates to be implemented as catalysis in devices such as fuel cell cathode materials. [ABSTRACT FROM AUTHOR]

Based on the third allotropic form of carbon (Fullerenes), we have studied novel allotropic carbon structures with a closed cage configuration (quasi-fullerenes) by using DFT at the B3LYP/6-31G(d) theory level. Such carbon C n-q structures (where, n = 20, 42, 48 and 60), combine states of hybridization sp 1 and sp 2 to form different member rings in their structure. A comparative analysis of quasi-fullerenes with respect to their isomers of greater stability (Fullerenes) was also performed to determine the relative stability of these clusters. Chemical Stability and reactivity were evaluated with the following criteria: aromaticity, hardness, chemical potential, sites of nucleophilic/electrophilic attack and HOMO-LUMO gaps. The results showed new isomerism of carbon nanostructures with rich chemical properties due to its different member rings. We also studied thermal stability with Lagrangian molecular dynamics using Atom Centered Density Matrix Propagation (ADMP) method. [ABSTRACT FROM AUTHOR]

This DFT study examined the interaction of a sulfated zirconia (SZ) slab model system (heterogeneous catalyst) and triacetin (a precursor in biodiesel production) using explicit methanol solvent molecules. Full geometry optimizations of the systems were performed at the B3LYP level of theory. Gibbs free energies provide insight into the spontaneity of the reactions along a three-step reaction mechanism for the transesterification of triacetin. Charge decomposition analysis revealed electronic charge transfer between the metallic oxide and the organic moieties involved in the reaction mechanism. Fukui indices indicate the likely locations on the SZ surface where catalysis may occur. The quadratic synchronous transit scheme was used to locate transition structures for each step of the transesterification process. The results are in agreement with the strongly acidic catalytic character of zirconium observed experimentally in the production of biodiesel. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

This review is intended to cover the works related to the anthocyanin behavior in food that is subjected to drying. Both experimental and theoretical results available in scientific literature are discussed. An increase in anthocyanin concentration has been observed upon thermal processing. Nevertheless, a conclusive explanation is still unavailable. The accessible studies suggest an increase in concentration during maturations, which could be related to the enzymatic activity. The possible enzymes involved in such a procedure have also been covered, including their role played in the process. The possible activation mechanisms and the related factors such as temperature, pH, oxygen contents and the presence of UV-light irradiation were also considered. Moreover, the metabolic pathways were also explored including experimental evaluation and theoretical models based on atomistic methodologies such as density functional theory (DFT). This review is aimed to provide a comprehensive overview of the probable mechanisms behind the increase of anthocyanin concentration during drying. • An adequate selection of solar filters may improve anthocyanin retention. • Anthocyanin stability and solar drying may be affected by physicochemical variables. • Electronic structure methods are capable to model anthocyanin degradation upon drying. • Electronic transfer is fundamental to understanding the kinetics of anthocyanins. [ABSTRACT FROM AUTHOR]

The prediction of the series of [AuXM] compounds (with X = H, F, Cl, Br, I and M = Li, Na, K, Rb, Cs) has been carried out by ab initio and DFT calculations. The systems are chemically stable due to their high chemical hardness. An unusual Au-Au attraction was found on each of the compounds along the series, addressing a strong metalophilic interaction of the aurophilic type. A strong aromatic character on the center of the [AuX] ring was also detected in the compounds under study, enhancing the stability of the species. The mechanism behind the bonding of the systems is mainly ruled by an electrostatic interaction among the 2 M cations and the [AuX] monolayer sheet in accordance with CDA and Ziegler analysis; only a slight orbital contribution yielded by back-donation from the alkaline metals to the [AuX] monolayer sheet is involved. It was shown that the [AuClM] group has the highest Fukui indexes, indicating that a catalytic reaction may rise from an electrophilic attack centered at the Au atoms or a nucleophilic attack on the alkaline-earth metals. The latter was tested with the most stable system of this group, namely [AuClLi], allowing it to interact with a CO molecule; the optimized [AuClLi] [CO] system represents a bound state that highlights the reactive properties of the species. An extended ...-M-S-M-S-M-... (with S representing the [AuX] system) linear chain model was also predicted at DFT level. Considering its spatial representation of the frontier molecular orbitals, it was found that a possible electronic transfer along the chain may take place via the triggering of an electron, suggesting the existence of a nanowire. [ABSTRACT FROM AUTHOR]

An ab initio, systematic study on the aromaticity involving the group of metalated extended porphyrins, termed meso-hexakis(pentafluorophenyl)-substituted[26]hexaphyrin(1.1.1.1.1.1) (HP), was performed for the first time. The aromatic behavior of the system shifted to antiaromatic in the [28]HP analogue, due to the presence of hydrogen atoms that break the orbital symmetry. The absorption bands observed in the experiment were assigned to an intraligand charge transfer, where the intrametallic character is also important. The excited states reveal the absorption of visible light and the possibility of electronic transfer to different systems. We propose a system such as single-walled carbon nanohorns (SWCNHs), due to their special electronic properties, and predict a novel nanohybrid material. The evidence of electronic communication between both species is presented in this work. The HP aromaticity and the spatial configuration of the interaction with SWCNHs are also related to the strength of electronic transfer among the systems, making the HP metalated antiaromatic species and their corresponding nanohybrids potential candidates to be used as building blocks in photovoltaic cell materials. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The task of creating a remarkably stable and effective electrochemical catalyst for efficient hydrogen evolution is arduous, primarily due to the multitude of factors that need to be taken into account for the industrial utilization of Pt. In this work, hybrid formation through in - s i t u reduction of Pt onto biogenic porous silica (Pt-SiO 2) is tested for its use as an efficient catalyst for hydrogen production. Exceptionally high electrocatalytic activity and excellent reusability of catalysts up to 200 cycles have been demonstrated. Pt-SiO 2 with low Pt content of 0.48 to 0.82 at% with active catalytic sites exhibit superior catalytic activity with a Tafel slope of 22 mV dec−1 and an overpotential of 28 mV (vs. RHE at 10 mA cm−2) as compared to the Pt wire and previously reported bare Pt-SiO 2 (0.65 at% and 0.48 at% of Pt), and hybrid (Pt/Ag) structures formed onto two different biogenic porous SiO 2 substrates. The best catalytic performance of the Pt 1 Ag 3 cluster, representing a low Pt concentration, has been validated by Density Functional Theory (DFT) calculations. Here, the high production from the Pt 1 Ag 3 cluster is assigned to the mutual synergistic effect between Pt/Ag atoms. The Pt atoms transfer the excess charge to the nearest Ag neighbors inside the cluster, facilitating hydrogen diffusion on the activated sites. These important findings authenticate the superior hydrogen production at reduced Pt concentration on amine-functionalized biogenic porous silica.   [ABSTRACT FROM AUTHOR]

Density functional theory and molecular dynamics (MD) calculations were used to evaluate electronic structure properties in a series of nanotubes with smallest possible diameters (both types: armchair and zigzag), and the corresponding chiral nanotubes (8,m) for 0 ≤ m ≤ 8. The calculations were performed considering a length of 16.5 Å. We evaluated a set of 26 combinations of dual nanotubes (armchair/armchair, zigzag/zigzag, armchair/zigzag, and zigzag/armchair), where the first label corresponds to the outer tube. We extended our study with nine additional systems of double‐walled carbon nanotubes (DWCNT) with semiconductor nature. In this regard, we gave insight into the semiconductive or metallic nature inherited to the dual tubes. DWCNT systems were possible to construct by maintaining a radial distance of 3.392 Å for the armchair/armchair arrangement and 3.526 Å for the zigzag/zigzag type. It was considered as a reference, the interplanar distance of graphite (3.350 Å). Electronic transport calculations were also performed on selected DWCNT systems in order to understand the role played by the different symmetries under study. It was evidenced that the electronic structure nature of the systems rules the ability to transport electrons through the DWCNT interface. [ABSTRACT FROM AUTHOR]

A combined theoretical and experimental study on a series of TiO 2 , lead sulfide (PbS) and PbS@TiO 2 nanocomposites was performed. TiO 2 structures were stabilized with simulated annealing using molecular dynamics at the ReaxFF level. A density functional theory study elucidated relevant electronic structure properties. We performed the study for a series of TiO 2 ) n , where n = 18 , 28, 38, 76 and 114. Band gaps ranging from 1.2 to 2.2 eV were found. This range was attributed to the size of the TiO 2 cluster models used in the calculations, and some models became metallic at smaller sizes. We synthesized TiO 2 nanoparticles of anatase (101) facet, which were characterized with pair distribution functions, in excellent agreement with the theoretical results. We explored the possibility to anchor a PbS quantum dot with a TiO 2 model system. This intermolecular interaction was relevant, since the composite material could be used in solid-state devices' applications, in which stability in the formation of the PbS / TiO 2 interface plays an important role for the device performance. The possibility to form a PbS@TiO 2 composite material was evidenced, via a covalent interaction, with contributions of the van der Waals type. [ABSTRACT FROM AUTHOR]

With the aid of density functional theory (DFT) calculations, different models of porous carbon monolayers were proposed for the development of anode materials for lithium-ion batteries (LIB). Special attention was given to the pore size effect in the storage process and diffusion of Li ions. Porous carbon models were formed from the pristine graphene structure, by removing carbon atoms that mimic the pore formation. DFT calculations showed that the fundamental planar structure of graphene is preserved upon pore formation. The electronic structure properties of carbon are drastically altered with the enlargement of the pore size according to the introduced vacancies, allowing effective Li-ion adsorption in larger pores. Calculations based on atoms in molecules theory indicate that the Li ions interact with the pores via an electrostatic-type attraction, comparable to that of a hydrogen bonding. The porous carbon models exhibit the availability to retain a massive number of Li ions at the surface by keeping the original planarity of graphene. This is intimately related to an enhanced theoretical specific capacity that raises with increasing pore size. Such capacities are in close agreement with experimental data. Therefore, the formation of the pores improves Li ions diffusion compared to the pristine graphene. This is of special interest for the design of improved anode materials for Li ion batteries. This theoretical methodology can be applied as an auxiliary tool to tailor porous carbon materials intended to be used in Li ion batteries. [Display omitted] • The presence of porosity in carbon monolayers improves the Li+ ion diffusion. • Electronic delocalization in the porous carbon models enhanced Li+ ions adsorption. • The AIM analysis shows that the Li+ is easily adsorbed in the pore periphery. • Porous carbon is susceptible to adsorb larger number of Li+ ions on the surface. • Specific capacity and open circuit voltage are competitive with other anode materials. [ABSTRACT FROM AUTHOR]

Manganese oxide (MnO 2) as an electrode material in energy storage devices has been used in supercapacitor electrodes because of its high capacitance and its sensitivity to the electrolyte chosen. In this work, density functional theory (DFT) calculations have been performed to understand the influence of the electrolyte MNO 3 with different metal cations (M =Li, Na, K) and the presence of water molecules on the α -MnO 2 surface. Through exploration of the potential energy surface, the relative energies involved in the diffusion process of M cations were described. The electronic density of states and the charge density differences allowed us to identify that the KNO 3 electrolyte improves charge accumulation in the α -MnO 2 structure. Quantum capacitance was calculated as an additional descriptor to elucidate the influence of the electronic structure properties on α -MnO 2 during the charging process. This theoretical modeling provides a comprehensive framework for understanding the mechanisms behind the ion charge transfer within the electrolyte. In particular, its interaction with the surface of the electrodes and the related pseudocapacitive properties. This work also provides insight into the charge/discharge processes of the electrode at the atomic level and may serve as a tool to tailor novel materials for energy storage devices. [Display omitted] • Manganese oxide offers high capacitance and sensitivity to chosen electrolytes. • DFT calculations show KNO 3 electrolyte enhances charge accumulation in α -MnO 2 structure. • Quantum capacitance suggests the electrolyte performance in α -MnO 2 as an electrode. • DFT provides insight into atomic-level charge/discharge processes in electrode α -MnO 2 [ABSTRACT FROM AUTHOR]

[Display omitted] • First experimental-theoretical study of CO oxidation on AuCu/TiO 2. • Enhanced stability of Au NPs due to migration of Cu species to the surface. • In-situ Raman highlights TiO 2 reducibility during the reaction. • DFT calculations confirmed the close interaction between metals and support. • Restructuration of the catalysts due to the CO interaction was unveiled. Bimetallic AuCu/TiO 2 catalysts were thoroughly studied during the CO oxidation reaction via three in-situ spectroscopic techniques (FTIR, UV–Vis and Raman) and density functional theory (DFT) calculations. Samples were synthesized through the deposition–precipitation with urea (DPU) method, and ex-situ characterized by several techniques. The superior catalytic activity displayed by the AuCu/TiO 2 sample was associated with the presence of nanoparticles in the form of heterodimers composed of the Au and Cu X O phases in close interaction with the TiO 2 support. In-situ DRIFTS results indicated that gold nanoparticles (NPs) presented some restructuration in the monometallic sample, while this event did not occur in the bimetallic one. The better stability on the AuCu/TiO 2 catalyst was related to the partial migration of Cu X O species to the surface of the NPs, also confirmed through in-situ UV–Vis spectroscopy. The favorable role played by the TiO 2 reducibility was established through in-situ Raman spectroscopy. Moreover, findings obtained by DFT confirmed the experimentally evidenced structural modifications. [ABSTRACT FROM AUTHOR]

This work gives new evidence on the structural properties of tetragonal hybrid perovskites obtained from different experimental routes of synthesis, and the theoretical elucidation of their electronic structure properties in accordance to the formation of the energy band gaps. Two different synthesis routes to prepare hybrid perovskites of the form (CH 3 NH 3 PbI 3) have been performed. The final crystal structure depends on the conditions of the preparation method that give the perovskite a twisted or regular molecular structure. This was certified by the structural analysis, normal modes of vibration, and opto-electronic properties. Moreover, the elucidation of electronic structure properties were also analyzed by a first principles study. That is, density functional theory (DFT) calculations revealed the structure configuration of twisted hybrid perovskites CH 3 NH 3 PbI 3 , in combination with XRD evidence. The electronic structure properties of the systems under study are mainly ruled by the geometrical disposition of the organic cation, whose different degrees of freedom are intimately related to the size of the energy band gap, and also to the magnitude of the work function. The DFT analysis with the experimental characterization of these hybrid perovskite systems could aid to tailor novel materials intended to be applied in the new generation of solar cell devices. That is, our combined methodology could contribute to modify the structure of perovskites with improved electronic properties for solar energy applications. [Display omitted] • The slow solvent evaporation process showed an iodine atom deviation. • CH 3 NH 3 PbI 3 optoelectronic properties were impacted by two synthesis methods. • DFT calculations revealed that the organic cation plays a role on gap formation. • Theoretical work functions are sensitive to the atomic interactions with the substrate. • Absorption spectra showed that twisted perovskites could act as an absorber material. [ABSTRACT FROM AUTHOR]

Increasing the electrochemical performance of electrode materials in sodium ion batteries (NIBs) remains a major challenge. Here, a combined experimental and theoretical investigation on the modification induced by Sb 2 S 3 embedded in a heteroatom-doped 3D carbon matrix (CM) for efficient anodes in NIBs is presented. The structural and chemical characterization demonstrates the successful doping of 3D CM with S and Sb atoms. When evaluated as anode materials for NIBs, the heteroatom-doped nanocomposites delivered a better cycling stability and superior rate capability than those of undoped Sb 2 S 3 /CM anodes. First principle calculations were used at the Density Functional Theory level to systematically study the Sb 2 S 3 /CM and Sb 2 S 3 /heteroatom doped-CM composites, as NIBs anodes. Doping the carbon substrate by heteroatoms improved the adsorption of Sb 2 S 3 on the matrix and allowed for ionic/covalent attraction with the Sb 2 S 3 nanoparticle, respectively. Such results could be used to model the stabilty of the composite architectures observed in the experiment, for superior cycling stability. [ABSTRACT FROM AUTHOR]

A Density Functional study predicting a heterogeneous-catalyzed reaction to obtain biodiesel was performed. Triacetin simulated triglycerides in the presence of an Au(1 1 1) surface as the heterogeneous catalyst. Methoxy was implemented as alcohol solvent to understand the reaction trajectory along a three-step transesterification process. Reactants and products in the three-step process are adsorbed on the Au substrate through non-covalent interactions of the electrostatic-type, which are also mediated by a van der Waals attraction. Density of states indicated that the electronic structure nature of Au is preserved after the interaction with the organic moieties. This may be addressed to an enhanced stability of the Au(1 1 1) catalyst through the overall reaction. Charge transfer analysis revealed that the Au surface oxidation aids in the transesterification of triacetin and evidences that gold plays an important role in this catalytic process. Such results may provide fundamental insights into the design of heterogeneous catalysts for biodiesel production. [ABSTRACT FROM AUTHOR]

Composite materials consisting of TiO 2 and graphene (TiO 2 /GR) have exciting properties that could make them suitable as anode material for Li-ion batteries. Systematic density functional theory (DFT) calculations were performed to investigate the TiO 2 /GR energy-storage mechanism, adsorption sites and diffusion pathways of Li ions in TiO 2 /GR. Its interface and the region outside graphene were studied for identifying stable surface sites. The adsorption energies are dominated by van der Waals interactions. Li diffusion along the graphene plane was the most favorable with a diffusion energy barrier of 0.24 eV, whereas the probability of diffusion at the interface is low, due to the barrier of 3 eV. The composite exhibited a higher specific charge-storage capacity than other van der Waals heterostructures. The TiO 2 /GR interface retains a large amount of charge implying that the TiO 2 /GR composite shows suitable electrochemical properties for use as anode in lithium-ion batteries. • DFT calculations explained energy storage processes in composite anodes. • The interaction at the TiO 2 /GR interface is mainly ruled by vdW effects. • Diffusion pathways of Li showed possible intercalation mechanisms in TiO 2 /GR anodes. • The potential 3.35V(Max)/1.85(Min) on TiO 2 /GR is adequate for electronic devices. [ABSTRACT FROM AUTHOR]

Organic solar cell nanomaterials are molecular systems that have been recently incorporated in devices with remarkable properties and high efficiencies. A systematic theoretical study based on density functional theory and non-equilibrium Green's functions was performed to elucidate the electron transport behavior on solar cell materials. The I − V profiles based on the transmission obtained from the electronic density revealed an appropriate performance in simulated conditions of sunlight irradiation, while in dark conditions such systems may behave as a diode. The current methodology may represent a tool to select and design high performance materials for the new generation of solar cell devices. [Display omitted] • Organic photovoltaic molecules were screened by their photoisomerization properties. • DFT revealed the transmission behavior at ground/excited states in screened systems. • Ground and excited states may represent dark/illumination conditions, respectively. • Electron transport in OPV systems could be finely simulated with a ballistic model. • The theoretical model may aid to identify OPV systems with improved performance. [ABSTRACT FROM AUTHOR]

Pristine γ -graphyne (γ -GY) is a widely known two-dimensional system that has a high Li, Na, and K adsorption capacity with high energy barriers for the diffusion of such metal ions. In this work, we used dispersion-corrected density functional theory calculations to investigate the electronic effect of Au-doped γ -graphyne (GYE-Au and GY-Au) monolayers on the adsorption and diffusion of M metal-ions (M = Li, Na, and K). The nature of the electronic structure of the GYE-Au monolayers corresponds to a semi-metallic behavior. According to climbing image nudge elastic band calculations, low activation energies in the diffusion of M atoms are associated with the presence of the Au atom with respect to the γ -GY monolayer. High adsorption energy values were associated with the storage capacity of the GYE-Au monolayers. The electronic storage properties such as open circuit voltage and theoretical specific capacity were improved in the GYE-Au monolayers. This study shows that, at an atomistic level, the GYE-Au monolayers could be an excellent 2D anode material for Li, Na, and K-ion batteries. [Display omitted] • Novel graphyne monolayers with Au-heteroatom were theoretically predicted. • The Li+, Na+, and K+ ions can be absorbed at sites close to the Au atom. • The effect of the Au atoms reduces energy barriers in alkaline ions diffusion. • B, N, and Au dopants improve the diffusion coefficient with respect to the graphyne. • Specific capacities are competitive with respect to known 2D anode materials. [ABSTRACT FROM AUTHOR]

A combined theoretical and experimental work was performed to assess the carbon dioxide (CO 2) evolution reaction into short chain hydrocarbons. The theoretical calculations were performed by using Density Functional Theory (DFT) at the DFT + U level. The reaction mechanisms were elucidated with the string method by comparing the photocatalytic behavior of the pristine Ti-NT surface, previously synthesized in our group, and the M -doped Ti-NT (M -Ti-NT, where M = Cu, Ni) systems. For the pristine material, the results showed lower adsorption energies of the CO 2 molecule (−0.27 eV), as compared to that obtained with the M -doped Ti- NT systems. Ni-Ti-NT showed an enhancement in photocatalytic performance with respect to the other surfaces, by yielding small activation energies throughout the reaction path. On the experimental side, Ti-NT and M -Ti-NT (M = Cu, Ni) materials were characterized through several techniques to assess their structural, morphological, textural, and optoelectronic properties. The photocatalytic CO 2 reduction was evaluated under wavelength illumination between 440–540 nm. The liquid solar fuel identified products were HCOOH, CH 2 O, and CH 3 OH, showing a different distribution among photocatalysts which correlates with the position of the conduction band of the photocatalysts. Doping with Cu and Ni of the Ti-NT structure enhances the carriers' density which improves the photoactivity mainly in the case of Ni-Ti-NT. The photocatalytic experimental results agree with the theoretical calculations. [Display omitted] • DFT calculations evidence the CO 2 reduction path on modified M–Ti–NT-based material. • Ni and Cu doping tunes the optoelectronic properties of Ti–NT. • Enhanced charge carriers density in M–Ti–NT improves the CO 2 conversion. • Ni–Ti–NT exhibits better photocatalytic activity. • Experimental evidence agrees with the proposed simulated reaction mechanism. [ABSTRACT FROM AUTHOR]

The use of glycerol as an added-value by-product from the transesterification of triglycerides to produce biodiesel has been the subject of intense research due to its versatility in a wide range of applications. In this work, a theoretical study at the density functional theory (DFT) level to categorize the most probable routes to achieve glycerol conversion was performed. Gibbs free energies were computed to assess the feasibility of the steps involved in experimental glycerol carbonate synthesis from glycerol and dimethyl carbonate. The cyclization from methyl glycerol carbonate anion to glycerol carbonate is reasonable due to the computation of the Gibbs free energy amounting to -310.0 kcal/mol, which indicates an exothermic reaction with the spontaneous rising of glycerol carbonate. The assessment of the molecular dimensions at the optimized geometry of glycerol carbonate showed a critical diameter and length of 5.25 Å and 5.90 Å, respectively; with a volume of 127.7 Å 3. Charge population analysis provided insights into the electronic transfer during the reaction and the bonding mechanism resulting in the products. Additionally, the heterogeneous catalysis reaction involved in the glycerol carbonate evolution reaction and its subproducts was studied on a periodic surface model of the oil palm fuel ash catalyst in order to evaluate activation energies and the feasibility of the proposed mechanism. That is, the computations revealed an activation energy barrier of 13.4 kcal/mol (0.58 eV), which also certifies the cyclization feasibility in the formation of glycerol carbonate. The results may contribute in the i n s i l i c o design of the experimental setup to improve efficiency in the process of transesterification reaction of glycerol and dimethyl carbonate to valuable glycerol carbonate. [Display omitted] • Quantum chemistry aids to improve efficiency on the conversion of glycerol carbonate. • Gibbs energies revealed the feasibility of the reaction steps in glycerol conversion. • Electronic density explains the mechanism of reaction to obtain a fuel additive. • Glycerol heterogeneous catalysis mechanism on OPFA surface are theoretically revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Photocatalytic potential of the Cu 2 O for (1 0 0), (1 1 0) and (1 1 1) facets is explored. • Cu 2 O(1 0 0) facet shows a high photocatalytic potential in the conversion of CO 2. • The reaction mechanism of the CO 2 towards methanol and methane is evaluated. • Simulations aids to understand the efficient conversion of CO 2 on the Cu 2 O(1 0 0) facet. In this work, Density Functional Theory (DFT) calculations were performed to elucidate the photocatalytic potential of Cu 2 O surfaces. Three slab models of the (1 0 0), (1 1 0) and (1 1 1) facets were studied by considering their optical and electronic structure properties, and photocatalytic potential. The results showed that Cu 2 O (1 0 0) and (1 1 1) surfaces e excellent candidates to be used in a photocatalytic processes to reduce CO 2 to form some hydrocarbon derivatives. Based on the photocatalytic potential analysis, the Cu 2 O(1 0 0) slab model was implemented to simulate the CO 2 reduction reaction evolution into methanol and methane with the String methodology. The results showed that such Cu 2 O facet could be efficiently implemented to improve the CO 2 photoreduction process. Additionally, this theoretical model could also be implemented to tailor novel photocatalytic materials to produce sustainable solar fuels. [ABSTRACT FROM AUTHOR]

• A theoretical DFT methodology may be used to tailor novel solar cell devices. • Lowest-energy structures at ground and excited states were computed in OPV materials. • Dihedral angles related to shifting of absorption maxima in UV–vis simulated spectra. • Descriptors obtained from electronic structure may aid to improve PV efficiencies. A density functional theory study was performed on a series of organic photovoltaic materials with a promising potential to be implemented as the active layer in a solar cell device. A thorough analysis on the molecular structure at ground and excited state revealed that some of the systems in the series of molecules observed in the ground state is dramatically altered in the first excitation. The dihedral deviations could be addressed as a ruling mechanism behind isomerization and its influence in the opto-electronic properties. The computation of absorption spectra at ground and excited state geometries showed a significant shift in the absorption maxima, presumably due to such geometrical changes. Furthermore, the computation of dipole moments gave us insights into the possible charge transfer from the OPV material to an acceptor in a solar cell device. This is critical when the system is implemented in such a device. Additionally, relevant photovoltaic parameters were collected, and a candidate series of OPV systems was proposed as potential materials for the heterojunctions of a solar cell device. The given theoretical methodology and the photovoltaic data computationally obtained may aid in the in silico design of novel donor materials for the new generation of solar cells. [ABSTRACT FROM AUTHOR]

A systematic theoretical study on graphene oxide model systems was performed with Density Functional Theory (DFT), and supported by experimental evidence. The results revealed that graphene is highly susceptible to be decorated with organic functional groups, which induced the formation of a band gap, and the rising of a novel semiconducting character. This novel property was used to explore the possible photocatalytic potential in the model systems under study. That is, we evaluated work functions to theoretically obtain the energies of the valence band maximum and the conduction band minimum with respect to the normal hydrogen electrode potential. The assessment of UV-vis profile via Time-dependent DFT also showed the potential of the model systems to efficiently absorb sun light irradiation under photocatalytic conditions. Moreover, the results showed that it is possible to tune the photocatalytic potential of the graphene oxide models under study by interchanging the functional groups anchored on the graphene surface, and their corresponding contents ratio. Experimental evidence obtained via the measurement of optoelectronic properties, revealed that it is possible to classify a graphene oxide powder into one of the model systems under study, while a photocatalytic procedure performed in our laboratory, showed the facile photoreduction of formic acid into methanol with such a graphene oxide. Consequently, the prediction of the electronic structure properties is expected. This may represent a tool to design materials based on graphene oxide to be implemented in reactors for photocatalytic applications. [ABSTRACT FROM AUTHOR]

The deterioration of food quality during food processing has been the subject of intense research. Changes in the secondary metabolites present in foodstuff have been identified during drying (phenolic and anthocyanin compounds). To explain the effect of temperature on the phenolic and anthocyanin content in strawberries during drying, a molecular dynamics simulation study at the Density Functional Theory (DFT) level was performed and validated with experimental data. Solar drying and tray drying at different temperatures were investigated. The total phenolic compounds (TPC), anthocyanins, and antioxidant activity were measured. Aromaticity indexes were obtained to rank the stability during the simulated drying process. The changes observed in the aromatic behavior were related to destabilization of the compounds, which leads to the degradation process observed experimentally. These results are of utility in the selection of the operating conditions to prevent TPC deterioration and to understand the role played by the electronic structure properties of anthocyanin molecules on their degradation. • DFT calculations gave insights into the understanding of anthocyanin degradation. • AIMD simulations explored possible routes of anthocyanin evolution during drying. • A combined method may aid into the design of food processing subjected to drying. • Total phenolic compounds and anthocyanins were influenced by the drying temperature. • Exposure time are related to changes in phenolic compounds formation. [ABSTRACT FROM AUTHOR]

Correlations among atomic structure, chemical reactivity, charge transfer and electronic structure properties were investigated in nanoporous carbon at different mass densities. The model structures have been generated by a heat-quench procedure using Density Functional Theory calculations and first-principles quantum molecular dynamics simulations. Reactive points seem to be highly dependent of the local structure of the material. The results showed that sponge-like nanoporous carbons are good candidates to graft polyoxometalates since they presented a stronger interaction with the carbon substrate. The charge transfer is from the nanoporous carbon to the polyoxometalate and a covalent interaction was observed for a density of 0.75 g/cm3. Our materials developed an electronic band around the Fermi level. Unlabelled Image • Assessment of reactivity on carbon substrates revealed directionality of bonding. • Curved graphitized geometries in carbon materials act as donor in charge transfer. • Electronic density of states showed degree of hybridization in a nanoporous carbons. • The bonding selectivity of oxides is highly sensitive to nanoporous carbon density. [ABSTRACT FROM AUTHOR]