Positive Binding Energy Research Articles

Biexcitons and quadrons in self-assembled quantum dots

We theoretically study biexcitons and quadrons in quantum dots with parabolic confinement and give a complete comparison between the two excitations. The calculation of quadron and biexciton binding energies as functions of electron-to-hole confinement potentials and mass ratios, using the unrestricted Hartree–Fock method, shows the essential differences between biexcitons and quadrons. The crossover between the negative and positive binding energies is indicated. The effect of an external magnetic field on the quadron and biexciton binding energies has also been investigated. In addition, the crossover between anti-binding and binding of both excited quadron and biexciton states in a certain range of the electron-to-hole oscillator length ratios has been found.

A novel LDHs-VB3- inhibitor for rebar corrosion in simulated concrete pore solution: Synthesis, performance and mechanism

Developing novel chloride-trapping inhibitors is of great significance for enhancing the durability of marine concrete structures. In this study, a novel LDHs-VB3- inhibitor was synthesized through the ion exchange method. Then, the corrosion inhibition mechanism of LDHs-VB3- inhibitor for rebar in the whole process of release - capture - adsorption - retardation was studied using experiments and density functional theory (DFT) simulations. The chloride ion exchange test demonstrates that the LDHs-VB3- inhibitor has a chloride trapping capacity of 35.5 mg/g in the saturated Ca(OH)2 solution containing 0.14 M NaCl, implying that it could capture Cl- in concrete pore solution. According to the electrochemical tests, the critical chloride concentration of rebar in the simulated concrete solution containing LDHs-VB3- falls within a range of 0.22 M–0.28 M, which is much higher than that in the solution without LDHs-VB3- (0.10 M–0.14 M). DFT simulations indicate that LDHs-VB3- exhibits more positive binding energy and uneven binding forces in contrast to LDHs-Cl-. Consequently, VB3- could be easily replaced by Cl- and then released into the pore solution of concrete. Moreover, the released VB3- could adsorb on the α-Fe2O3 surface in a concrete environment via the interaction of surface Fe atoms with N and O atoms of VB3-. The preadsorbed VB3- could diminish the interaction of Cl- with the α-Fe2O3 surface by reducing electron transfer, thereby mitigating the risk of passive film breakdown and retarding the chloride-induced corrosion of rebars.

Tailoring TiO2 finite nanotubes: Doping-induced modulation of electronic, optical, and hydrogen storage properties

In this study, we employ density functional theory calculations to investigate the properties of finite single walled TiO2 finite nanotubes (TiO2NTs). The constructed nanotubes demonstrate geometric stability, as evidenced by positive binding energy and real positive vibrational frequencies obtained from the infrared spectra. Substitutional doping with various atoms (B, N, C, Si, Li, Sc, Fe, and Cu) introduces intriguing effects on the electronic and optical properties of TiO2NTs. Doping with Fe slightly reduces the wide energy gap (∼5 eV) of unmodified TiO2NTs to 4.2 eV, while Si doping significantly decreases the energy gap by half. Furthermore, we investigate the impact of doping TiO2NTs with boron, carbon, nitrogen, iron, cesium, and silicon on their UV–Vis absorption spectra. The introduction of these dopants induces significant redshifts in the absorption peaks, indicating alterations in the electronic energy gap and transitions between specific states. These findings provide valuable insights into the structural and electronic modifications of TiO2NTs. Moreover, we explore the adsorption properties of TiO2NTs for H2 molecules. While unmodified TiO2NTs exhibit low adsorption energy, doping with a small number of C or Si atoms leads to a substantial enhancement in the adsorption energy. Specifically, Si doping achieves adsorption energy of approximately 0.2 eV, accompanied by a hydrogen storage capacity of 6.1 wt%, exceeding the standard capacity of 6.0 wt%. Importantly, the desorption temperature remains comparable to room temperature, ensuring long-term recyclability. These results highlight the potential of doped single-walled TiO2 nanotubes as efficient hydrogen storage devices.

Electronic and optical properties of chemically modified 2D GaAs nanoribbons

We employed density functional theory calculations to investigate the electronic and optical characteristics of finite GaAs nanoribbons (NRs). Our study encompasses chemical alterations including doping, functionalization, and complete passivation, aimed at tailoring NR properties. The structural stability of these NRs was affirmed by detecting real vibrational frequencies in infrared spectra, indicating dynamical stability. Positive binding energies further corroborated the robust formation of NRs. Analysis of doped GaAs nanoribbons revealed a diverse range of energy gaps (approximately 2.672 to 5.132 eV). The introduction of F atoms through passivation extended the gap to 5.132 eV, while Cu atoms introduced via edge doping reduced it to 2.672 eV. A density of states analysis indicated that As atom orbitals primarily contributed to occupied molecular orbitals, while Ga atom orbitals significantly influenced unoccupied states. This suggested As atoms as electron donors and Ga atoms as electron acceptors in potential interactions. We investigated excited-state electron–hole interactions through various indices, including electron–hole overlap and charge-transfer length. These insights enriched our understanding of these interactions. Notably, UV–Vis absorption spectra exhibited intriguing phenomena. Doping with Te, Cu, W, and Mo induced redshifts, while functionalization induced red/blue shifts in GaAs-34NR spectra. Passivation, functionalization, and doping collectively enhanced electrical conductivity, highlighting the potential for improving material properties. Among the compounds studied, GaAs-34NR-edg-Cu demonstrated the highest electrical conductivity, while GaAs-34NR displayed the lowest. In summary, our comprehensive investigation offers valuable insights into customizing GaAs nanoribbon characteristics, with promising implications for nanoelectronics and optoelectronics applications.

Resonance enhancement of the electromagnetic interaction between two charged particles in the bound state in the continuum

In bound states in the continuum (BIC) the mass of a composite particle is greater than the total mass of its constituents. The BIC state is investigated in a system of two charged particles [Formula: see text] and [Formula: see text] with different masses ([Formula: see text]), using the ladder Bethe–Salpeter equation. We demonstrate that there are two momentum space regions for the positive binding energy, in which the electromagnetic interaction between the particles is strongly enhanced, and the effective coupling constant turns out to be equal to [Formula: see text], where [Formula: see text] is the fine structure constant. The interaction resonance confines the constituents in the BIC state with the positive binding energy, which is of the order of the mass of the lighter particle from this pair.

Electronic and Optical Properties of Finite Gallium Sulfide Nano Ribbons: A First-Principles Study

The electronic and optical properties of finite GaS nanoribbons are investigated using density functional theory calculations. The effect of size, edge termination, and chemical modification by doping and edge passivation are taken into account. The dynamical stability is confirmed by the positive vibration frequency from infrared spectra; further, the positive binding energies ensure the stable formation of the considered nanoribbons. Accurate control of the energy gap has been achieved. For instance, in armchair nanoribbons, energy gaps ranging from ~ 1 to 4 eV were obtained in varying sizes. Moreover, the energy gap can be increased by up to 5.98 eV through edge passivation with F-atoms or decreased to 0.98 eV through doping with Si-atoms. The density of states shows that the occupied molecular orbitals are dominated by S-atoms orbitals, while unoccupied ones are mostly contributed to by Ga orbitals. Thus, S-atoms will be the electron donor sites, and Ga-atoms will be the electron acceptors in the interactions that the nanoribbons might undergo. The nature of electron–hole interactions in the excited states was investigated using various indices, such as electron–hole overlapping, charge–transfer length, and hole–electron Coulomb attraction energy. The UV-Vis absorption spectra reveal a redshift by increasing the size in the armchair or the zigzag directions. Chemical functionalization shows a significant influence on the absorption spectra, where a redshift or blueshift can be achieved depending on the dopant or the attached element.

First-Principles Study of MoS2, WS2, and NbS2 Quantum Dots: Electronic Properties and Hydrogen Evolution Reaction

The electronic and catalytic properties of two-dimensional MoS2, WS2, and NbS2 quantum dots are investigated using density functional theory investigations. The stability of the considered structures is confirmed by the positive binding energies and the real vibrational frequencies in the infrared spectra. The ab initio molecular dynamics simulations show that these nanodots are thermally stable at 300 K with negligible changes in the potential energy and metal–S bonds. The pristine nanodots are semiconductors with energy gaps ranging from 2.6 to 3 eV. Edge sulfuration significantly decreases the energy gap of MoS2 and WS2 to 1.85 and 0.75 eV, respectively. The decrease is a result of the evolution of low-energy molecular orbitals by the passivating S-atoms. The energy gap of NbS2 is not affected, which could be due to the spin doublet state. Molecular electrostatic potentials reveal that the edge sulfur/transition metal atoms are electrophilic/nucleophilic sites, while the surface atoms are almost neutral sites. MoS2 quantum dots show an interestingly low change in the hydrogen adsorption free energy ~0.007 eV, which makes them competitive for hydrogen evolution catalysts.

Negative donor impurity polarizability and stability in quantum dot under a lateral electric field

The binding energies of the ground and excited states of negative (D−) and neutral (D0) donor impurities in a parabolic cylindrical quantum dot (CQD) are calculated within single-band effective mass approximations. The quantum variational method is used to solve the time-independent Schrödinger equation for centered and off-centered impurities under the effect of a lateral electric field. Based on the calculated negative or positive binding energies, the stability of D− and D0 is discussed. The results show that at a specific lateral electric field strength, each D− is switched from a bound (stable) to an unbound (unstable) state in the CQD and differs for centered and off-centered D−. Using the calculated energies and wave functions, the response of the CQD static dipole polarizability (SDP) to the lateral electric field strength is investigated. The results show that CQD size, lateral electric field strength, and lateral electric field direction have a noticeable influence on polarizability. The D− polarizability is found to decrease with increasing lateral electric field strength but shows different behavior with increasing CQD radius.

The Electron-Proton Bound State in the Continuum with the Positive Binding Energy of 1.531 of the Electron Mass

The Electron-Proton Bound State in the Continuum with the Positive Binding Energy of 1.531 of the Electron Mass

Virtual Screening of FDA-Approved Drugs for Enhanced Binding with Mitochondrial Aldehyde Dehydrogenase.

Mitochondrial aldehyde dehydrogenase (ALDH2) is a potential target for the treatment of substance use disorders such as alcohol addiction. Here, we adopted computational methods of molecular dynamics (MD) simulation, docking, and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) analysis to perform a virtual screening of FDA-approved drugs, hitting potent inhibitors against ALDH2. Using MD-derived conformations as receptors, butenafine (net charge q = +1 e) and olaparib (q = 0) were selected as promising compounds with a low toxicity and a binding strength equal to or stronger than previously reported potent inhibitors of daidzin and CVT-10216. A few negatively charged compounds were also hit from the docking with the Autodock Vina software, while the MM-PBSA analysis yielded positive binding energies (unfavorable binding) for these compounds, mainly owing to electrostatic repulsion in association with a negatively charged receptor (q = -6 e for ALDH2 plus the cofactor NAD+). This revealed a deficiency of the Vina scoring in dealing with strong charge-charge interactions between binding partners, due to its built-in protocol of not using atomic charges for electrostatic interactions. These observations indicated a requirement of further verification using MD and/or MM-PBSA after docking prediction. The identification of key residues for the binding implied that the receptor residues at the bottom and entrance of the substrate-binding hydrophobic tunnel were able to offer additional interactions with different inhibitors such as π-π, π-alkyl, van der Waals contacts, and polar interactions, and that the rational use of these interactions is beneficial to the design of potent inhibitors against ALDH2.

Enhanced electron transfer due to rGO makes Ag–CaTiO3@rGO a promising plasmonic photocatalyst

Herein, the synthesis of a new ternary nanocomposite, Ag–CaTiO 3 @rGO, exhibiting high photocatalytic dye degradation efficiency is reported. The photocatalytic activity of Ag–CaTiO 3 @rGO was studied under natural sunlight with a model dye pollutant sulforhodamine B. This photocatalyst's high degradation efficiency is attributed to the synergistic effect of plasmon-induced visible light-harvesting due to Ag and enhanced adsorption and electron–transport properties due to rGO. It is found that the Ag-induced surface plasmon characteristics of the nanocomposites are sensitive to rGO concentration. Absorption spectra of the nanocomposites indicated that Ag and rGO enhance and extend the absorbance in the visible region, which is beneficial for creating photo-carriers during the photocatalytic reaction under sunlight. In the X-ray photoelectron spectra, ∼0.7–0.8 eV positive binding energy shift is observed in Ca 2p, Ti 2p, and O 1s peaks of typical Ag–CaTiO 3 @rGO compared to Ag–CaTiO 3 and CaTiO 3 , indicating that electrons are transferred to the electron acceptor, rGO. The reusability of this photocatalyst Ag–CaTiO 3 @rGO was analyzed by conducting repeated dye degradation tests. The adsorption characteristics of the designed catalyst followed the Langmuir isotherm model. A model for the plausible mechanism of enhanced sunlight-driven photocatalysis by Ag–CaTiO 3 @rGO with 7.5 wt% GO is also proposed.

Enhancement of thermal properties of Kevlar 29 coated by SiC and TiO2 nanoparticles and their binding energy analysis

In the fields of military research, aerospace, and vehicle technology, the thermal stability of Kevlar fiber is critical for improving its flame resistance. In this work, the pad mangle machine was used to improve the thermal properties of Kevlar 29 in order to expand the range of applications for thermal aspects. Silicon carbide and titanium oxide nanoparticles provide thermal stability on the fiber surface through intermolecular adhesion. Here, 5 wt% and 10 wt% of nanoparticles with various mass ratios (1:1) have been chosen. Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) analysis, and X-ray Photoelectron Spectroscopy (XPS) analysis have all been used to measure different thermal properties. The surface morphology of samples is represented by FESEM analysis, while the active organic groups are represented by FTIR analysis. The greater crystallization of epoxy and nanoparticles is linked to post-heat treatment of the material. The glass transition temperature of the coated samples shifted maximum from 559.13 °C to 580.51 °C, the end set temperature increased by 30.67 °C compared to the uncoated sample, and the residual weight changed from 29.77 percent to 4.06 percent, according to the findings (i.e., lightweight). When compared to the uncoated sample, the coated sample's enthalpy increased significantly (i.e., the samples can absorb more heat). The smaller the positive binding energy, the higher the activation energy, and hence the slower the chemical reaction, which is especially important in high-temperature applications. Finally, this research reveals a 4.5–5.2 percent increase in thermal characteristics.

Passivating the pH-Responsive Sites to Configure a Widely pH-Stable Emulsifier for High-Efficiency Benzyl Alcohol Oxidation.

Widely pH-stable emulsions configured by solid emulsifiers with high chemical stabilities and anti-corrosion properties under strong acid or alkaline conditions are highly sought after for practical and wide application of Pickering interfacial catalysis. Herein, a unique strategy was reported for synthesis of a widely pH-stable and novel emulsifier by passivating the pH-responsive sites on graphene oxide nanoribbon (GONR) surface using ionic liquid (IL). The suitable wettability of GONR-IL was derived from the positive binding energy between IL and water, which ensured the stability of the emulsion in a wide pH range. Benefiting from the passivated surface chemistry of GONR, the emulsion microreactor stabilized by GONR-IL exhibited a remarkable stability over a wide range of pH values. A GONR-IL-supported Pd catalyst stabilized at the toluene-water interface achieved an excellent emulsion catalytic activity for benzyl alcohol oxidation (conversion of 92 %), which was exceedingly higher than that of Pd/GONR (<1 %), Pd/CNTs-IL (51 %), or Pd/GO-IL (8 %).

Classical Electrostatics Remains the Driving Force for Interanion Hydrogen and Halogen Bonding.

Interanion hydrogen bonding (IAHB) and halogen bonding (IAXB) have emerged as a counterintuitive linker in a range of fascinating applications. Despite the overall repulsive (positive) binding energy, anions are trapped in a local minimum with its corresponding transition state (TS) preventing dissociation. In other words, the adduct of anions is metastable. Seemingly, the electrostatic paradigm and force field description of hydrogen/halogen bonding (HB/XB) are challenged, because of the preconceived Coulombic repulsion. Aiming at an insightful understanding of these interanion phenomena, we employed the energy decomposition approach based on the block-localized wavefunction method (BLW-ED) to investigate a series of exemplary interanion complexes. As expected, the key distinction from the conventional HB/XB lies in the electrostatic interaction, which is not increasingly repulsive as anions gradually approach to each other. Rather, there is a Coulombic barrier at a certain point. After this point, the electrostatic repulsion diminishes with the decreasing distance between anions. Differently, other energy components vary monotonically just like in conventional cases. The nonmonotonic characteristic of the electrostatic interaction in interanion complexes was reproduced using the multipole expansion in AMOEBA polarizable force field in which the state-specified atomic multipoles were adopted. This suggests that the nonmonotonicity can be well interpreted by classical electrostatic theory and there is no conceptual difference between conventional HB/XB and IAHB/IAXB. The stability of IAHB/IAXB depends on the competition between the local attractive HB/XB and the global Coulombic repulsion of net charges, though there is cooperativity between these two contrasting forces. This concise model was supported by the attractive IAHB/IAXB in modified molecular capsules, which exhibit strong quadruple HB/XBs and a considerable distance between charged substituents.

Iron-iron oxide supported palladium catalyst for the interconversion of formate and carbon dioxide

Synthesized palladium-coated iron-iron oxide (Fe@FeOx/Pd) nanoparticles (NPs) using the successive salt reduction method are tested for their activity and stability toward formate oxidation (FO) and electrochemical CO2 reduction to formate (eCO2RF). The experimental results for FO show a current density at 0.12 V vs. Ag/AgCl of 1.65 mA/cm2 over 1 h, which is 16 times higher than that for Pd NPs. Furthermore, the same catalyst displays a higher current density with a faradaic efficiency (FE) of 95.6 % toward the eCO2RF, and exhibits a lower degree of CO adsorption. The iron-iron oxide interaction with the overlayer palladium is characterized by TEM/EDX, XPS/UPS, Mössbauer spectroscopy, and electrochemical techniques such as cyclic voltammetry (CV) and chronoamperometry (CA). NMR is used to estimate the amount of formate produced by the eCO2RF. A positive binding energy shift of the Pd 3d peak and the upshift of the d-band center as measured by XPS compared to monometallic homemade Pd NPs confirm that the electronic perturbation of the catalyst surface plays a major role in enhancing the performance of Fe@FeOx/Pd for both FO and eCO2RF. Furthermore, the work function as measured by UPS for the Fe@FeOx/Pd material is lower than that for monometallic Pd confirming a change in chemical properties of the catalyst surface. Finally, Mössbauer spectroscopy is used to determine the composition, structure and nature of all sites of the Fe@FeOx substrate before use and the perturbation of their intrinsic properties by the Pd overlayer. This change in intrinsic properties of the Pd coated material provides additional explanations for the electrochemical improvement measured for this catalyst toward both FO and eCO2RF

In silico assessment of dehalogenase from Bacillus thuringiensis H2 in relation to its salinity-stability and pollutants degradation

Increased scientific interest has led to the rise in biotechnological uses of halophilic and halotolerant microbes for hypersaline wastewater bioremediation. Hence, this study performed molecular docking, molecular dynamic (MD) simulations, and validation by Molecular Mechanic Poisson-Boltzmann Surface Area (MM-PBSA) calculations on the DehH2 from Bacillus thuringiensis H2. We aimed to identify the interactions of DehH2 with substrates haloacids, haloacetates, and chlorpyrifos under extreme salinity (35% NaCl). MD simulations revealed that DehH2 preferentially degraded haloacids and haloacetates (−6.3 to −4.7 kcal/mol) by forming three or four hydrogen bonds to the catalytic triad, Asp125, Arg201, and Lys202. Conversely, chlorpyrifos was the least preferred substrate in both MD simulations and MM-PBSA calculations. MD simulation results ranked the DehH2-L-2CP complex (RMSD □0.125−0.23 nm) as the most stable while the least was the DehH2-chlorpyrifos complex (RMSD 0.32 nm; RMSF 0.0 − 0.29). The order of stability was as follows: DehH2-L-2CP > DehH2-MCA > DehH2-D-2CP > DehH2-3CP > DehH2-2,2-DCP > DehH2-2,3-DCP > DehH2-TCA > DehH2-chlorpyrifos. The MM-PBSA calculations further affirmed the DehH2-L-2CP complex's highest stability with the lowest binding energy of −45.14 kcal/mol, followed closely by DehH2-MCA (−41.21 kcal/mol), DehH2-D-2CP (−31.59 kcal/mol), DehH2-3CP (−30.75 kcal/mol), DehH2-2,2- DCP (−29.72 kcal/mol), DehH2-2,3-DCP (−22.20 kcal/mol) and DehH2-TCA (−18.46 kcal/mol). The positive binding energy of the DehH2-chlorpyrifos complex (+180.57 kcal/mol) proved the enzyme's non-preference for the substrate. The results ultimately illustrated the unique specificity of the DehH2 to degrade the above-said pollutants under a hypersaline condition. Communicated by Ramaswamy H. Sarma

Computational analysis of atomic binding energy for organosilicon‐ low‐density polyethylene‐coated silica embedded in polyvinylidene fluoride composite membrane for membrane gas absorption

In an effort to enhance the wetting resistance and chemical stability of membrane contactors, silica nanoparticles (SiNP) have been incorporated into polyvinylidene fluoride (PVDF) membrane. These SiNP have been hydrophobically functionalized with three separate organosilicons (hexamethyldisilane, dimethyldichlorosilane, and polydimethylsiloxane) to produce TS-530, TS-610, and TS-720 SiNP. Then, they were coated with low-density polyethylene (LDPE) before adding them to the membrane casting dope. Using HyperChem, the molecular interaction between SiNP, organosilicons, and LDPE, as well as their aggregation tendency, was predicted using a semi-empirical computational approach (PM3). Both theoretical predictions and experimental results show that TS-610 and TS-720 SiNP have a high propensity to agglomerate, leading to the formation of composite membranes with large macrovoids. The HyperChem analysis, however, also indicates that LDPE/f-SiNP can resist chemical corrosion, and all composite membranes show positive binding energy interactions with amines. This enables the LDPE/f-SiNP membranes to perform better than the neat PVDF membrane with an adequate amine solution, and it remains hydrophobic after prolonged exposure.

Inhibition of SARS-CoV-2 main protease: a repurposing study that targets the dimer interface of the protein

Coronavirus disease-2019 (COVID-19) was firstly reported in Wuhan, China, towards the end of 2019, and emerged as a pandemic. The spread and lethality rates of the COVID-19 have ignited studies that focus on the development of therapeutics for either treatment or prophylaxis purposes. In parallel, drug repurposing studies have also come into prominence. Herein, we aimed at having a holistic understanding of conformational and dynamical changes induced by an experimentally characterized inhibitor on main protease (Mpro) which would enable the discovery of novel inhibitors. To this end, we performed molecular dynamics simulations using crystal structures of apo and α-ketoamide 13b-bound Mpro homodimer. Analysis of trajectories pertaining to apo Mpro revealed a new target site, which is located at the homodimer interface, next to the catalytic dyad. Thereafter, we performed ensemble-based virtual screening by exploiting the ZINC and DrugBank databases and identified three candidate molecules, namely eluxadoline, diosmin, and ZINC02948810 that could invoke local and global conformational rearrangements which were also elicited by α-ketoamide 13b on the catalytic dyad of Mpro. Furthermore, ZINC23881687 stably interacted with catalytically important residues Glu166 and Ser1 and the target site throughout the simulation. However, it gave positive binding energy, presumably, due to displaying higher flexibility that might dominate the entropic term, which is not included in the MM-PBSA method. Finally, ZINC20425029, whose mode of action was different, modulated dynamical properties of catalytically important residue, Ala285. As such, this study presents valuable findings that might be used in the development of novel therapeutics against Mpro. Communicated by Ramaswamy H. Sarma

Charmonium transition in electromagnetic and rotational fields

We study charmonia in electromagnetic and rotational fields in the frame of a potential model. Different from the temperature field which is isotropic and leads to the well-known charmonium dissociation, the electromagnetic and rotational fields break down the radial symmetry, and the competition between strong interaction and electromagnetic and rotational interaction in the direction of Lorentz force makes the charmonia transit from an isotropic bound state of strong interaction with positive binding energy to an anisotropic bound state of electromagnetic and rotational interaction with negative binding energy. The transition seems possible to be realized in high energy nuclear collisions.

From nuclei to neutron stars: simple binding energy computer modelling in the classroom (part 1)

We present a simple activity based on the liquid-drop model which allows secondary school students to explore the uses of mathematical models and gain an intuitive understanding of the concept of binding energy, and in particular the significance of positive binding energy. Using spreadsheets provided as supplementary material, students can perform simple manipulations on the different coefficients of the model to understand the role of each of its five terms. Students can use the spreadsheets to determine model parameters by optimising the agreement with real atomic mass data. This activity can be used as the starting point of a discussion about theoretical models, their validation when it comes to describing experimental data and their predictive power towards unexplored regimes.