The importance of online exposure when applying for a job

The rapid growth and development of information and communication technologies enabled the transition to a global and dynamic communication model. Among the many communication tools that have emerged, online social networks have proven to be the most popular. Its success has to do with the ability to converge several features into a single space, allowing users to share knowledge and experiences, maintain contact with their peers, as well as communicate freely and spontaneously. However, using these virtual platforms we are, inevitably, creating an online history that can affect our personal and professional lives. Facing a difficult and competitive job market, companies seek to capture the best talents, within their list of job candidates. In this context, companies are starting to screen online profiles to validate candidates’ personal characteristics in a non-professional environment. The main purpose of this study is to understand the importance of the activities in online social networks when applying for a job, especially among recent graduates, who are seeking their first professional experience. Results show that even though recent graduates take caution when using social networking sites, especially Facebook, online exposure is not considered an important factor when undergoing employment processes.info:eu-repo/semantics/publishedVersio

The importance of online exposure when applying for a job

The rapid growth and development of information and communication technologies enabled the transition to a global and dynamic communication model. Among the many communication tools that have emerged, online social networks have proven to be the most popular. Its success has to do with the ability to converge several features into a single space, allowing users to share knowledge and experiences, maintain contact with their peers, as well as communicate freely and spontaneously. However, using these virtual platforms we are, inevitably, creating an online history that can affect our personal and professional lives. Facing a difficult and competitive job market, companies seek to capture the best talents, within their list of job candidates. In this context, companies are starting to screen online profiles to validate candidates’ personal characteristics in a non-professional environment. The main purpose of this study is to understand the importance of the activities in online social networks when applying for a job, especially among recent graduates, who are seeking their first professional experience. Results show that even though recent graduates take caution when using social networking sites, especially Facebook, online exposure is not considered an important factor when undergoing employment processes.info:eu-repo/semantics/publishedVersio

An empirical, yet practical way to predict the band gap in solids by using density functional band structure calculations

Band structure calculations based on density functional theory (DFT) with local or gradient-corrected exchange-correlation potentials are known to severely underestimate the band gap of semiconducting and insulating materials. Alternative approaches have been proposed: from semiempirical setups, such as the so-called DFT +U, to hybrid density functionals using a fraction of nonlocal Fock exchange, to modifications of semilocal density functionals. However, the resulting methods appear to be material dependent and lack theoretical rigor. The rigorous many-body perturbation theory based on GW methods provides accurate results but at a very high computational cost. Hereby, we show that a linear correlation between the electronic band gaps obtained from standard DFT and GW approaches exists for most materials and argue that (1) this is a strong indication that the problem of predicting band gaps from standard DFT calculation arises from the assignment of a physical meaning to the Kohn-Sham energy levels rather than from intrinsic errors of the DFT methods and (2) it provides a practical way to obtain GW-like quality results from standard DFT calculations. The latter will be especially useful for systems where the unit cell involves a large number of atoms as in the case of doped or defect-containing materials for which GW calculations become unfeasible

Morphology of TiO2 nanoparticles as fingerprint for the transient absorption spectra: implications for photocatalysis

Understanding the relationship between structural properties and the character of the charged carriers in photoactive TiO2 nanoparticles is fundamental to improving their photocatalytic activity. Transient absorption spectroscopy (TAS) is often used to explore the character of the charge carriers, but carrying out experiments on well-defined nanoparticles with a given morphology and selected size is extremely difficult. Here, hybrid time-dependent density functional theory based calculations carried out for realistic TiO2 nanoparticles (NPs) with bipyramidal, truncated, and spherical morphologies reveal that the electron-trapped carriers are quite sensitive to the NP morphology. In particular, these carriers are shallowly trapped in faceted NPs whereas they are deeply trapped in those exhibiting a spherical morphology. In addition, the simulated absorption spectra can be compared directly to experimental ones obtained by TAS, thus allowing additional information to be provided regarding the morphology of the TiO2 NPs in a given sample. Note that although the present study focuses on TiO2 nanoparticles, it can be easily extended to other photoactive materials such as ZnO or WO3 NPs thus allowing the extraction of information regarding the relationship between the NP morphology and the nature of the low-lying excited states

Theoretical modeling of electronic excitations of gas-phase and solvated TiO2 nanoclusters and nanoparticles of interest in photocatalysis

The optical absorption spectra of (TiO2)n, nanoclusters (n = 1-20) and nanoparticles (n = 35, 84) have been calculated from the frequency-dependent dielectric function in the independent particle approximation under the framework of density functional theory. The PBE generalized gradient approach based functional, the so-called PBE+U method and the PBE0 and PBEx hybrid functionals containing 25% and 12.5% of nonlocal Fock exchange, respectively have been used. The simulated spectra have been obtained in the gas phase and in water on previously PBE0 optimized atomic structures. The effect of the solvent has been accounted for by using an implicit water solvation model. For the smallest nanoclusters, the spectra show discrete peaks, whereas for the largest nanoclusters and for the nanoparticles they resemble a continuum absorption band. In the gas phase and for a given density functional, the onset of the absorption (optical gap, Ogap) remains relatively constant for all nanoparticle sizes although it increases with the percentage of nonlocal Fock exchange, as expected. For all tested functionals, the tendency of Ogap in water is very similar to that observed in the gas phase with an almost constant upshift. For comparison, the optical gap has also been calculated at the TD-DFT level with the PBEx functional in the gas phase and in water. Both approaches agree reasonably well although the TD-DFT gap values are lower than those derived from the dielectric-function. Overall, the position of the spectral maxima and the width of the spectra are relatively constant and independent of particle size which may have implications in the understanding of photocatalysis by TiO2

Electronic properties of realistic anatase TiO2 nanoparticles from G(0)W(0) calculations on a Gaussian and plane waves scheme

The electronic properties of realistic (TiO2)n nanoparticles (NPs) with cuboctahedral and bipyramidal morphologies are investigated within the many-body perturbation theory (MBPT) G0W0 approximation using PBE and hybrid PBEx (12.5% Fock contribution) functionals as starting points. The use of a Gaussian and plane waves (GPW) scheme reduces the usual O4 computational time required in this type of calculation close to O3 and thus allows considering explicitly NPs with n up to 165. The analysis of the Kohn-Sham energy orbitals and quasiparticle (QP) energies shows that the optical energy gap (Ogap), the electronic energy gap (Egap), and the exciton binding energy (ΔEex) values decrease with increasing TiO2 NP size, in agreement with previous work. However, while bipyramidal NPs appear to reach the scalable regime already for n = 84, cuboctahedral NPs reach this regime only above n = 151. Relevant correlations are found and reported that will allow one to predict these electronic properties at the G0W0 level in even much larger NPs where these calculations are unaffordable. The present work provides a feasible and practical way to approach the electronic properties of rather large TiO2 NPs and thus constitutes a further step in the study of realistic nanoparticles of semiconducting oxides

Investigating the character of excited states in TiO2 nanoparticles from topological descriptors: implications for photocatalysis

Titanium dioxide (TiO2) nanoclusters (NCs) and nanoparticles (NPs) have been the focus of intense research in recent years since they play a prominent role in photocatalysis. In particular, the properties of their excited states determine the photocatalytic activity. Among the requirements for photocatalytic activity, low excitation energy and large separation of the charge carriers are crucial. While information regarding the first is straightforward from either experiment or theory, the information regarding the second is scarce or missing. In the present work we fill this gap through a topological analysis of the first singlet excited state of a series of TiO2 NCs, and anatase and rutile derived NPs containing up to 495 atoms. The excited states of all these systems in vacuo have been obtained from time-dependent density functional theory (TDDFT) calculations using hybrid functionals and the influence of water was taken into account through a continuum model. Three different topological descriptors based on the attachment/detachment one-electron charge density, are scrutinized: (i) charge transfer degree, (ii) charge density overlap, and (iii) distance between centroids of charge. The present analysis shows that the charge separation in the excited state strongly depends on the NP size and shape. The character of the electronic excitations, as arising from the analysis of the canonical Kohn-Sham molecular orbitals (MOs) or from natural transition orbitals (NTOs), is also investigated. The understanding and prediction of charge transfer and recombination in TiO2 nanostructures may have implications in the rational design of these systems to boost their photocatalytic potential

Barnes Update Applied in the Gauss−Newton Method: An Improved Algorithm to Locate Bond Breaking Points

A mechanochemical reaction is a reaction induced by mechanical energy. A general accepted model for this type of reactions consists in a first order perturbation on the associated potential energy surface (PES) of the unperturbed molecular system due to mechanical stress or pulling force. Within this theoretical framework, the so-called optimal barrier breakdown points or optimal bond breaking points (BBPs) are critical points of the unperturbed PES where the Hessian matrix has a zero eigenvector that coincides with the gradient vector. Optimal BBPs are 'catastrophe points' that are par- ticularly important because its associated gradient indicates how to optimally harness tensile forces to induce reactions by transforming a chemical reaction into a barrierless process. Building on a previous method based on a nonlinear least squares minimiza- tion to locate BBPs (Bofill et al., J. Chem. Phys. 2017, 147, 152710-10), we propose a new algorithm to locate BBPs of any molecular system based on the Gauss-Newton method combined with the Barnes update for the nonsymmetric Jacobian matrix, which is shown to be more appropriate than the Broyden update. The efficiency of the new method is demonstrated for a multidimensional model PES and two medium size molec- ular systems of interest in enzymatic catalysis and mechanochemistry

Adsorption and dissociation of molecular hydrogen on orthorhombic β- Mo2C and cubic δ-MoC (001) surfaces

Molybdenum carbides are increasingly used in heterogeneously catalyzed hydrogenation reactions, which imply the adsorption and dissociation of molecular hydrogen. Here a systematic density functional theory based study, including or excluding dispersion terms, concerning the interaction and stability of H2 with cubic δ-MoC(001) and orthorhombic β-Mo2C(001) surfaces is presented. In the latter case the two possible C or Mo terminations are considered. In addition, different situations for the H covered surfaces are examined. Computational results including dispersive forces predict as essentially spontaneous dissociation of H2 on β-Mo2C(001) independently of the surface termination, whereas on δ-MoC(001) molecular hydrogen dissociation implies a small but noticeable energy barrier. Furthermore, the ab initio thermodynamics formalism has been used to compare the stability of different H coverages. Finally, core level binding energies and vibrational frequencies are presented with the aim to assist the interpretation of yet unavailable data from X-ray photoelectron and infrared spectroscopies

Interplay between the gentlest ascent dynamics method and conjugate directions to locate transition states

An algorithm to locate transition states on a potential energy surface (PES) is proposed and described. The technique is based on the GAD method where the gradient of the PES is projected into a given direction and also perpendicular to it. In the proposed method, named GAD-CD, the projection is not only applied to the gradient but also to the Hessian matrix. Then, the resulting Hessian matrix is block diagonal. The direction is updated according to the GAD method. Furthermore, to ensure stability and to avoid a high computational cost, a trust region technique is incorporated and the Hessian matrix is updated at each iteration. The performance of the algorithm in comparison with the standard ascent dynamics is discussed for a simple two dimensional model PES. Its efficiency for describing the reaction mechanisms involving small and medium size molecular systems is demonstrated for five molecular systems of interest