Theoretical study of the catalytic hydrodeoxygenation of furan, methylfuran and benzofurane on MoS.

Herein, we have studied the direct deoxygenation (DDO) (without prior hydrogenation) of furan, 2-methylfuran and benzofuran on the metal edge of MoS with a vacancy created under pressure of dihydrogen. For the three molecules, we found that the desorption of the water molecule for the regeneration of the vacancy is the most endothermic. Based on the thermodynamic and kinetic aspects, the reactivity order of the oxygenated compounds is furan ≈ 2-methylfuran > benzofuran, which is in agreement with literature.

Gold(I)-Thiolate Coordination Polymers as Multifunctional Materials: The Case of Au(I)--Fluorothiophenolate.

Gold-sulfur interaction has vital importance in nanotechnologies and material chemistry to design functional nanoparticles, self-assembled monolayers, or molecular complexes. In this paper, a mixture of only two basic precursors, such as the chloroauric acid (HAu(III)Cl) and a thiol molecule (-fluorothiophenol (-HSPhF)), are used for the synthesis of gold(I)-thiolate coordination polymers. Under different conditions of synthesis and external stimuli, five different functional materials with different states of [Au(I)(-SPhF)] can be afforded.

Elucidating Solvatochromic Shifts in Two-Dimensional Photocatalysts by Solving the Bethe-Salpeter Equation Coupled with Implicit Solvation Method.

Many studies have focused on tailoring the photophysical properties of two-dimensional (2D) materials for photocatalytic (PC) or photoelectrochemical (PEC) applications. To understand the optical properties of 2D materials in solution, we established a computational method that combined the Bethe-Salpeter equation (BSE) calculations with our GW-GPE method, allowing for GW/BSE-level calculations with implicit solvation described using the generalized Poisson equation (GPE). We applied this method to MoS, phosphorene (PP), and -CN and found that when the solvent dielectric increased, it reduced the exciton binding energy and quasiparticle bandgap, resulting in almost no solvatochromic shift in the excitonic peaks of MoS and PP, which is consistent with previous experiments.

Jahn-Teller distortion, octahedra rotations and orbital ordering in perovskites: KScF as a model system.

The KScF perovskite has been used as a model for investigating the relative importance of the Jahn-Teller (JT) lift of degeneracy, the ScF octahedra rotation (OR), and the quadrupole-quadrupole interaction linked to different occupancy of the Sc t subshell in various sites of the unit cell (orbital ordering, OO). The group-subgroup sequence , , , and , supplemented by and , has been explored by using an Gaussian type basis set, hybrid functionals, and the CRYSTAL17 code. The JT lift of degeneracy provides a stabilization about 5 times larger than the sum of the OO and OR effects.

Tuning the electronic and optical properties of small organic acenedithiophene molecular crystals for photovoltaic applications: First principles calculations.

Periodic density functional theory was employed to investigate the impact of chemical modifications on the properties of π-conjugated acenedithiophene molecular crystals. Here, we highlight the importance of the β-methylthionation effect, the position of the sulfur atoms of the thiacycle group and their size, and the number of central benzene rings in the chemical modification strategy. Our results show that the introduction of the methylthio groups at the β-positions of the thiophene and the additional benzene ring at the center of the BDT crystal structure are a promising strategy to improve the performance of organic semiconductors, as observed experimentally.

Solving the Schrödinger Equation in the Configuration Space with Generative Machine Learning.

The configuration interaction approach provides a conceptually simple and powerful approach to solve the Schrödinger equation for realistic molecules and materials but is characterized by an unfavorable scaling, which strongly limits its practical applicability. Effectively selecting only the configurations that actually contribute to the wave function is a fundamental step toward practical applications. We propose a machine learning approach that iteratively trains a generative model to preferentially generate the important configurations.

First-principles study of the structural and electronic properties of tetragonal ZrOX (X = S, Se, and Te) monolayers and their vdW heterostructures for applications in optoelectronics and photocatalysis.

Using first-principles calculations, we have studied the structural and electronic properties of ZrOX (X = S, Se, and Te) monolayers and their van der Waals heterostructures in the tetragonal structure. Our results show that these monolayers are dynamically stable and are semiconductors with electronic bandgaps ranging from 1.98 to 3.

investigations of a CoBiS monolayer with and without point defects.

Through density functional theory (DFT) calculations, a new triclinic monolayer, namely CoBiS, with higher stability than that of penta-CoBiS, is predicted. Our results show that this monolayer is a nonmagnetic metallic compound. To tune its magnetic properties, we systematically investigated the formation and energetics of different point defects in the CoBiS monolayer, such as V, V and V.

molecular dynamics investigation of the co-adsorption of iodine species with CO and HO in silver-exchanged chabazite.

In the field of nuclear energy, there is particular interest for the trapping of harmful iodine species (I and CHI) that could be released during a nuclear accident, due to their dangereous impact on the human metabolic processes and the environment. Here, the adsorption of these iodine molecules several inhibitory compounds (CO, HO, CHCl and Cl) in the silver exchanged chabazite zeolite is studied in detail using molecular dynamics simulations at a realistic temperature and composition. Interestingly, we found that the iodine molecules remain attached to the cations even when the number of water molecules inside the structure is greater than two times the number of cations per cell at = 413 K.

GW Quasiparticle Energies and Bandgaps of Two-Dimensional Materials Immersed in Water.

Computational simulations have become of major interest to screen potential photocatalysts for optimal band edge positions which straddle the redox potentials. Unfortunately, these methods suffer from a difficulty in resolving the dynamic solvent response on the band edge positions. We have developed a computational method based on the GW approximation coupled with an implicit solvation model that solves a generalized Poisson equation (GPE), that is, GW-GPE.

Assessing the Accuracy of Machine Learning Thermodynamic Perturbation Theory: Density Functional Theory and Beyond.

Machine learning thermodynamic perturbation theory (MLPT) is a promising approach to compute finite temperature properties when the goal is to compare several different levels of theory and/or to apply highly expensive computational methods. Indeed, starting from a production molecular dynamics trajectory, this method can estimate properties at one or more target levels of theory from only a small number of additional fixed-geometry calculations, which are used to train a machine learning model. However, as MLPT is based on thermodynamic perturbation theory (TPT), inaccuracies might arise when the starting point trajectory samples a configurational space which has a small overlap with that of the target approximations of interest.

Establishing the accuracy of density functional approaches for the description of noncovalent interactions in ionic liquids.

We test a number of dispersion corrected versatile Generalized Gradient Approximation (GGA) and meta-GGA functionals for their ability to predict the interactions of ionic liquids, and show that most can achieve energies within 1 kcal mol of benchmarks. This compares favorably with an accurate dispersion corrected hybrid, ωB97X-V. Our tests also reveal that PBE (Perdew-Burke-Ernzerhof GGA) calculations using the plane-wave projector augmented wave method and Gaussian Type Orbitals (GTOs) differ by less than 0.

Structure and Energetics of Dye-Sensitized NiO Interfaces in Water from Ab Initio MD and Large-Scale GW Calculations.

The energy-level alignment across solvated molecule/semiconductor interfaces is a crucial property for the correct functioning of dye-sensitized photoelectrodes, where, following the absorption of solar light, a cascade of interfacial hole/electron transfer processes has to efficiently take place. In light of the difficulty of performing X-ray photoelectron spectroscopy measurements at the molecule/solvent/metal-oxide interface, being able to accurately predict the level alignment by first-principles calculations on realistic structural models would represent an important step toward the optimization of the device. In this respect, dye/NiO surfaces, employed in p-type dye-sensitized solar cells, are undoubtedly challenging for ab initio methods and, also for this reason, much less investigated than the n-type dye/TiO counterpart.

Assessment and prediction of band edge locations of nitrides using a self-consistent hybrid functional.

Due to their optimal bandgap size and large defect tolerance, nitrides are becoming pivotal materials in several optoelectronic devices, photovoltaics, and photocatalysts. A computational method that can accurately predict their electronic structures is indispensable for exploring new nitride materials. However, the relatively small bandgap of nitrides, which stems from the subtle balance between ionic and covalent bond characteristics, makes conventional density functional theory challenging to achieve satisfactory accuracy.

Hybrid localized graph kernel for machine learning energy-related properties of molecules and solids.

Nowadays, the coupling of electronic structure and machine learning techniques serves as a powerful tool to predict chemical and physical properties of a broad range of systems. With the aim of improving the accuracy of predictions, a large number of representations for molecules and solids for machine learning applications has been developed. In this work we propose a novel descriptor based on the notion of molecular graph.

Study of Helicity-Dependent Light-Induced Demagnetization: From the Optical Regime to the Extreme Ultraviolet Regime.

We use real-time time-dependent density functional theory to investigate the effect of optical and extreme ultraviolet (XUV) circularly polarized femtosecond pulses on the magnetization dynamics of ferromagnetic materials. We demonstrate that the light induces a helicity-dependent reduction of the magnitude of the magnetization. In the XUV regime, where the 3p semicore states are involved, a larger helicity dependence persisting even after the passage of light is exhibited.

Lifshitz Transition and Non-Fermi Liquid Behavior in Highly Doped Semimetals.

The classical Fermi liquid theory and Drude model have provided fundamental ways to understand the resistivity of most metals. The violation of the classical theory, known as non-Fermi liquid (NFL) transport, appears in certain metals, including topological semimetals, but quantitative understanding of the NFL behavior has not yet been established. In particular, the determination of the non-quadratic temperature exponent in the resistivity, a sign of NFL behavior, remains a puzzling issue.

Adsorption mechanisms of fatty acids on fluorite unraveled by infrared spectroscopy and first-principles calculations.

Hypothesis: The adsorption mechanisms of fatty acids on minerals are largely debated from years, and their understanding is now required to improve flotation processing in the critical context of raw materials. Three wavenumbers have been observed in the literature for the asymmetric stretching vibration of COO after the adsorption of fatty acids on mineral surfaces. They have been interpreted as different adsorbed forms, such as a precipitate formation, an adsorption of sole or bridged carboxylates, an anion exchange, or adsorbed modes, such as monodentate or bidentate configurations.

Establishing the accuracy of density functional approaches for the description of noncovalent interactions in biomolecules.

Biomolecules have complex structures, and noncovalent interactions are crucial to determine their conformations and functionalities. It is therefore critical to be able to describe them in an accurate but efficient manner in these systems. In this context density functional theory (DFT) could provide a powerful tool to simulate biological matter either directly for relatively simple systems or coupled with classical simulations like the QM/MM (quantum mechanics/molecular mechanics) approach.

Ternary Chalcogenides BaMTe (M = Cu, Ag): Syntheses, Modulated Crystal Structures, Optical Properties, and Electronic Calculations.

Standard solid-state methods produced black crystals of the compounds BaCuTe and BaAgTe at 1173 K; the crystal structures of each were established using single-crystal X-ray diffraction data. Both crystal structures are modulated. The compound BaCuTe crystallizes in the monoclinic superspace group 2(1/2)0, having cell dimensions of = 4.

Grafting of iron on amorphous silica surfaces from ab initio calculations.

Iron over silica catalytic systems have attracted considerable attention due to their activity and selectivity in different reactions, for instance, in the hydrodeoxygenation process. Here, the grafting mechanisms of iron under various forms (one atom, two atoms, or a cluster) on silica surfaces are studied using ab initio calculations. Various geometries with different locations of iron on the silica structure have been investigated, and it is found that a strong interaction between iron and the silanol groups takes place, mostly driven by the formation of Fe-O-Si bonds, and in few cases by nearby surface OH groups, creating Fe-OH-Si bonds.

Imprinting isolated single iron atoms onto mesoporous silica by templating with metallosurfactants.

Hypothesis: One of the main drawbacks of metal-supported materials, traditionally prepared by the impregnation of metal salts onto pre-synthesized porous supports, is the formation of large and unevenly dispersed particles. Generally, the larger are the particles, the lower is the number of catalytic sites. Maximum atom exposure can be reached within single-atom materials, which appear therefore as the next generation of porous catalysts.

Synergistic adsorptions of NaCO and NaSiO on calcium minerals revealed by spectroscopic and molecular dynamics studies.

The synergistic effects between sodium silicate (NaSiO) and sodium carbonate (NaCO) adsorbed on mineral surfaces are not yet understood, making it impossible to finely tune their respective amounts in various industrial processes. In order to unravel this phenomenon, diffuse reflectance infrared Fourier transform and X-ray photoelectron spectroscopies were combined with molecular dynamics to investigate the adsorption of NaSiO onto bare and carbonated fluorite (CaF), an archetypal calcium mineral. Both experimental and theoretical results proved that NaCO adsorbs onto CaF with a high affinity and forms a layer of NaCO on the surface.