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Hydrogen is a promising energy carrier, but its onboard application is limited by the need for compact, low-pressure storage solutions. Solid-state complex metal hydride systems, such as MgB 2 /Mg(BH 4) 2 , offer high storage capacities but suffer from sluggish kinetics and poor reversibility. One avenue for improving reactivity is to introduce metal dopants to alter electronic and atomic properties, but the role of these chemical additives remains poorly understood, particularly for the hydrogenation reaction. In this work, we used density functional theory calculations on model MgB 2 systems to rationalize the potential role of metal dopants in destabilizing B–B bonding within the MgB 2 lattice. We carried out detailed electronic structure analyses for 28 different metal dopant adatoms to identify properties that contribute to a dopant's efficacy. Based on the simulation results, we propose that an intermediate ionic and covalent character of the bonds between adatoms and B atoms is desirable for facilitating charge redistribution, disrupting the B–B bond network, and promoting H 2 dissociation and H atom chemisorption on MgB 2. [ABSTRACT FROM AUTHOR]

Strong and weak interatomic interactions in chemical and biological systems are ubiquitous, yet how to identify them on a unified theoretical foundation is still not well established. Recently, we proposed employing Pauli energy-based indexes, such as strong covalent interaction and bonding and noncovalent interaction indexes, in the framework of density functional theory for the purpose. In this work, we extend our previous theoretical work by directly employing Pauli energy, Pauli potential, Pauli force, and Pauli charge to simultaneously identify both strong covalent bonding and weak noncovalent interactions. Our results from this work elucidate that using their signature isosurfaces, we can identify different types of interactions, either strong or weak, including single, double, triple, and quadruple covalent bonds, ionic bond, metallic bond, hydrogen bonding, and van der Waals interaction. We also discovered strong linear correlations between Pauli energy derived quantities and different covalent bond orders. These qualitative and quantitative results from our present study solidify the viewpoint that a unified approach to simultaneously identify both strong and weak interactions is possible. In our view, this work signifies one step forward towards the goal of establishing a density-based theory of chemical reactivity in density functional theory. [ABSTRACT FROM AUTHOR]

Interlayers between a substrate and a functional film are used extensively to tailor film adhesion and avoid failure induced by delamination. With nitrogen doping increasingly used to improve the surface properties of steel, how to select appropriate interlayers for high film adhesion on substrate remains elusive in theory. Using spin-polarized density functional theory computations, the authors investigated the effects of N doping on the mechanical properties of Fe and its adhesion with widely used Cr, Ti, and Si interlayers. The results showed that N atoms doped at the Fe octahedron center increased hardness by 30% under 4 wt. % N. N atom at Cr/Fe, Ti/Fe, Si/Fe interfaces interestingly increased the interlayer adhesion of Ti/Fe and Si/Fe, while reducing that of Cr/Fe. This behavior is attributed to competition between magnetic coupling and atomic bonding. For Cr/Fe with strong magnetic coupling, the reduction in adhesion was resulted from doped N that inhibited magnetic coupling at the interface. For Ti/Fe and Si/Fe with weak magnetic coupling, the formation of covalent bonds at the interface by the N atom increased interfacial adhesion. This study provides insights into the nitrogen doping of steel and the selection of proper interlayers for strong film-substrate adhesion. [ABSTRACT FROM AUTHOR]

A cationic copper‐stabilized coppoborylene was prepared and structurally characterized via infrared photodissociation spectroscopy and density functional theory calculations. This structure exemplifies a new class of borylenes stabilized by three‐center‐two‐electron metal‐boron‐metal covalent bonding interaction, displaying exceptional σ‐acidity and unparalleled π‐donor capability for CO activation that outperforms all of the known transition metal cations and is comparable or even superior to the documented base‐trapped borylenes. Its neutral form represents a monovalent boron compound with a strongly reactive amphoteric boron center built on transition‐metal‐boron bonds, which inspires the design and synthesis of new members of the borylene family. [ABSTRACT FROM AUTHOR]

The interaction of H, H2, and MgH2 with graphene is investigated using the density functional theory to explore the possibility of exploiting graphene or functionalized graphene as a hydrogen storage medium. The H atom is positioned at various distances from the graphene surface and the energetics are computed in detail. The extent of interaction of the s electron of H with graphene's pz electrons is well brought out. Similar investigations are carried out for H2, MgH2. In the case of H atom, a HC covalent bond is formed. This process turns out to be a prerequisite for proton transfer through graphene. Interactions of H2 and MgH2 with graphene are different from that of H. It leads to the conclusion that functionalized graphene will better substrate/candidate for applications like hydrogen storage. [ABSTRACT FROM AUTHOR]

Achieving a harmonious balance between strength and plasticity is a long-standing problem in single-phase face-centered-cubic (fcc) high-entropy alloys (HEAs). Herein, in-situ TiC ceramic particle reinforced fcc-structured Fe 1.4 Co 0.8 Ni 0.8 Cr HEAs is designed and investigated by combining the experiments and first-principate calculations. The results show that the y (TiC)–Fe 1.4 Co 0.8 Ni 0.8 Cr (y = 0, 2.5, 5.0, 7.5 and 10.0 %, y: volume fraction) composites consist of fcc phase with submicron/micron TiC after the co-addition of Ti and C element, and the formation of TiC facilitates to refine the microstructure of the composites. Such microstructural evolutions significantly enhance the mechanical performances of the composites. Particularly, the 7.5 % (TiC)–Fe 1.4 Co 0.8 Ni 0.8 Cr composite exhibits a high yield strength of ∼562.7 ± 7.7 MPa and tensile strength of ∼971.3 ± 5.4 MPa, which are respectively increased by 169.0 % and 88.3 % as compared with the Fe 1.4 Co 0.8 Ni 0.8 Cr based alloy, yet with the fracture elongation decreases to 35.9 ± 0.3 %. The increment in yield strength is mainly driven from the combined effect of the grain refinement strengthening, dislocation strengthening and precipitation strengthening. Density functional theory (DFT) results reveal that the increase of C –Ti bonds and the formation of covalent bonds in the 7.5 % (TiC)–Fe 1.4 Co 0.8 Ni 0.8 Cr composite lead to relatively higher strength and lower ductility, which are well agreed with the experimental results. [ABSTRACT FROM AUTHOR]

Density functional theory calculations have been performed to compare the HCHO decomposition on Co3O4(110)-A and (110)-B terminations. The results showed that the energy barriers of the two C–H bond cleavages of HCHO on the (110)-A termination were lower than those on the (110)-B termination, suggesting that the (110)-A termination had stronger HCHO decomposition ability than the (110)-B termination. Electronic structures revealed that the stronger HCHO decomposition ability of the (110)-A termination might be ascribed to the strong covalent bond between HCHO and the (110)-A termination, as well as the higher d-band center of Co3+ ions on the (110)-A termination. Furthermore, we proposed that the preparation of Co3O4 under oxygen-rich growth conditions was beneficial to HCHO decomposition because the (110)-A termination was more stable under oxygen-rich conditions. [ABSTRACT FROM AUTHOR]

In the so-called Interacting Quantum Atoms (IQA) approach, the molecular energy is numerically decomposed as a sum of atomic and diatomic contributions. While proper formulations have been put forward for both Hartree–Fock and post-Hartree–Fock wavefunctions, this is not the case for the Kohn–Sham density functional theory (KS-DFT). In this work, we critically analyze the performance of two fully additive approaches for the IQA decomposition of the KS-DFT energy, namely, the one from Francisco et al., which uses atomic scaling factors, and that from Salvador and Mayer based upon the bond order density (SM-IQA). Atomic and diatomic exchange–correlation (xc) energy components are obtained for a molecular test set comprising different bond types and multiplicities and along the reaction coordinate of a Diels–Alder reaction. Both methodologies behave similarly for all systems considered. In general, the SM-IQA diatomic xc components are less negative than the Hartree–Fock ones, which is in good agreement with the known effect of electron correlation upon (most) covalent bonds. In addition, a new general scheme to minimize the numerical error of the sum of two-electron energy contributions (i.e., Coulomb and exact exchange) in the framework of overlapping atoms is described in detail. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT)-1/2 is an efficient bandgap rectification method for DFT under local density approximation (LDA) or generalized gradient approximation. It was suggested that non-self-consistent DFT-1/2 should be used for highly ionic insulators like LiF, whereas self-consistent DFT-1/2 should still be used for other compounds. Nevertheless, there is no quantitative criterion prescribed for which implementation should work for an arbitrary insulator, which leads to severe ambiguity in this method. In this work, we analyze the impact of self-consistency in DFT-1/2 and shell DFT-1/2 calculations in insulators or semiconductors with ionic bonds, covalent bonds, and intermediate cases and show that self-consistency is required even for highly ionic insulators for globally better electronic structure details. The self-energy correction renders electrons more localized around the anions in self-consistent LDA-1/2. The well-known delocalization error of LDA is rectified, but with strong overcorrection, due to the presence of additional self-energy potential. However, in non-self-consistent LDA-1/2 calculations, the electron wave functions indicate that such localization is much more severe and beyond a reasonable range because the strong Coulomb repulsion is not counted in the Hamiltonian. Another common drawback of non-self-consistent LDA-1/2 is that the ionicity of the bonding gets substantially enhanced, and the bandgap can be enormously high in mixed ionic-covalent compounds like TiO2. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations using ab initio methods at the MRCI+Q(8,9)/def2‐QZVPPD and CCSD(T)/def2‐QZVPPD levels as well as using density functional theory are reported for the diatomic molecules AeN− (Ae=Ca, Sr, Ba). The anions CaN− and SrN− have electronic triplet (3Π) ground states with nearly identical bond dissociation energies De ~57 kcal/mol calculated at the MRCI+Q(8,9)/def2‐QZVPPD level. In contrast, the heavier homologue BaN− has a singlet (1Σ+) ground state, which is only 1.1 kcal/mol below the triplet (3Σ−) state. The computed bond dissociation energy of (1Σ+) BaN− is 68.4 kcal/mol. The calculations at the CCSD(T)‐full/def2‐QZVPPD and BP86‐D3(BJ)/def2‐QZVPPD levels are in reasonable agreement with the MRCI+Q(8,9)/def2‐QZVPPD data, except for the singlet (1Σ+) state, which has a large multireference character. The calculated atomic partial charges given by the CM5, Voronoi and Hirshfeld methods suggest small to medium‐sized Ae←N− charge donation for most electronic states. In contrast, the NBO method predicts for all species medium to large Ae→N− electronic charge donation, which is due to the neglect of the (n)p AOs of Ae atoms as genuine valence orbitals. Neither the bond orders nor the bond lengths correlate with the bond dissociation energies. The EDA−NOCV calculations show that the heavier alkaline earth atoms Ca, Sr, Ba use their (n)s and (n‐1)d orbitals for covalent bonding. [ABSTRACT FROM AUTHOR]

Fatal pathogenic organisms have been detected by various point‐of‐care tests (PoCTs) in clinical samples. PoCTs based on portable electrical devices are able to detect organisms in simple and rapid method. Although electrical PoCT devices show ultra sensitivity when detecting pathogens in standard samples, their industrialization has been limited due to low reproducibility, sensitivity, and specificity, resulting from nonspecific binding issues by media. In this research, a perpendicular N‐heterocyclic carbene self‐assembled monolayer (NHC‐SAM) conjugated on graphene micropattern field‐effect transistors (NGMFETs) is first demonstrated for monitoring pathogens. Two single bonds of NHCSAM on GM are investigated via density functional theory (DFT) and surface analyses. Bioreceptors are conjugated on the side gate‐modulated NGMFET for ultra‐stable on‐site detection. The side‐gated BNGMFETs system displayed remarkable performance in the detection of the following: i) SARS‐CoV‐2 spike protein S1 (limit of detection (LOD): ≈10 pg mL−1) in CTM, ii) O. tsutsugamushi Ab (LOD: ≈1 pg mL−1), and iii) E. coli (LOD: 10° CFU mL−1) in serum. Compared to commercial methodology, the platform presents 102 times higher LODs towards those pathogens in clinical samples with higher reproducibility. Based on these results, side‐gated BNGMFETs can be utilized as universal PoCT during pandemics. [ABSTRACT FROM AUTHOR]

In the present work, 15 Mo/VC interfaces were investigated using first-principles calculations based on density functional theory. Four possible interface orientations, two terminations, and three stacking sites were considered. The adhesion energy (Wad) and interfacial energy (Eint) of these interface models were computed. The results indicate that the C-terminated hollow-site Mo(110)/VC(111) interface exhibits the highest stability with a larger Wad value of 10.64 J m−2 and the lowest Eint value of 2.98 J m−2, followed by the V-terminated central-site Mo(211)/VC(220) interface. Analysis of the electronic structure reveals the formation of strong polar covalent bonds at these interfaces. Additionally, simulations of tensile fracture processes were performed, demonstrating that at strains reaching 22% and 32%, respectively, the ideal tensile strengths for the C-terminated hollow-site Mo(110)/VC(111) interface and V-terminated central-site Mo(211)/VC(220) interface are ∼26.01 and 35.53 GPa. In particular, in the C-terminated hollow-site Mo(110)/VC(111) interface, fracture occurs in the Mo slabs due to concentrated strain when external strain is applied; meanwhile, uniform strain is observed in both Mo(211) and VC(200) slabs within this system. Notably, the V-terminated central-site Mo(211)/VC (220) interface demonstrates excellent tensile strength as well as toughness. These findings suggest that explaining solely based on adhesion work is insufficient to account for the observed tensile strength at these interfaces. [ABSTRACT FROM AUTHOR]

In industrial manufacturing, pyrrhotite(Fe1−xS), once depressed, is commonly activated for flotation. However, the replacement of CuSO4 is necessary due to the need for exact control over the dosage during the activation of pyrrhotite, which can pose challenges in industrial settings. This research introduces the use of FeSO4 for the first time to efficiently activate pyrrhotite. The impact of two different activators on pyrrhotite was examined through microflotation experiments and density functional theory (DFT) calculations. Microflotation experiments confirmed that as the CuSO4 dosage increased from 0 to 8 × 10−4 mol/L, the recovery of pyrrhotite initially increased slightly from 71.27% to 87.65% but then sharply decreased to 16.47%. Conversely, when the FeSO4 dosage was increased from 0 to 8 × 10−4 mol/L, pyrrhotite's recovery rose from 71.27% to 82.37%. These results indicate a higher sensitivity of CuSO4 to dosage variations, suggesting that minor alterations in dosage can significantly impact its efficacy under certain experimental conditions. In contrast, FeSO4 might demonstrate reduced sensitivity to changes in dosage, leading to more consistent performance. Fe ions can chemically adsorb onto the surface of pyrrhotite (001), creating a stable chemical bond, thereby markedly activating pyrrhotite. The addition of butyl xanthate (BX), coupled with the action of Fe2+ on activated pyrrhotite, results in the formation of four Fe-S bonds on Fe2+. The proximity of their atomic distances contributes to the development of a stable double-chelate structure. The S 3p orbital on BX hybridizes with the Fe 3d orbital on pyrrhotite, but the hybrid effect of Fe2+ activation is stronger than that of nonactivation. In addition, the Fe-S bond formed by the addition of activated Fe2+ has a higher Mulliken population, more charge overlap, and stronger covalent bonds. Therefore, Fe2+ is an excellent, efficient, and stable pyrrhotite activator. [ABSTRACT FROM AUTHOR]

The low index interfacial configuration, interface energy and electronic properties of NbC/α-Fe are calculated using the first-principles method based on density functional theory and ab initio molecular dynamics simulation. Additionally, the NbC/α-Fe interface with the low index interfacial configuration is calculated by two-dimensional disregistry method. It is demonstrated that the Fe-C type has an interface energy of -1.553 J/m², the smallest interface energy and the most stable structure, therefore the Fe-C type is the most stable conformation of the NbC(001)/α-Fe(001). Strong orbital resonance phenomenon exists between Fe-3d, Nb-4d and C-2p, producing strong metallic and covalent bonds. The results of disregistry calculation by different interfacial structures of NbC/α-Fe shows that the disregistry of NbC(001)/α-Fe(001) crystalline surface is the smallest at 10.19%, which corresponds to the results of interface energy calculation. It can be shown that the α-Fe(001) is the optimal orientation surface of the NbC(001). Herein, we have revealed the site-oriented and stable bonding mode relationship of NbC/α-Fe interface in steel, which provides important theoretical guidance to explore the mechanism of grain refinement of NbC particles in shipbuilding steels. [ABSTRACT FROM AUTHOR]

We investigate W–ZrC interfaces using first-principles calculations based on the density functional theory. There have been theoretical and experimental studies exploring W–ZrC interfaces, however, the debate regarding the most stable interface continues to persist. In this study, we systematically simulated various W–ZrC interfaces merging W and ZrC surfaces with different orientations. Subsequently, we evaluated their stabilities and explained the corresponding stabilities in terms of the nature of bonding and charge-transfer processes at the interface. We find ZrC(111)–W(110) is the most stable interface with higher adhesive energy than the other interfaces. The additional stability associated with the ZrC(111)–W(110) results from significant interface reconstruction. Three layers of W and ZrC adjacent to the interface are involved in the charge-transfer process leading to stronger ionic bonds in ZrC(111)–W(110) as compared to the other potential candidate: ZrC(100)–W(100). The C and W atoms are found to be displaced from their symmetric position during the reconstruction process at the interface to facilitate stronger bonds with shorter W–C and W–Zr bonds in ZrC(111)–W(110) as compared to ZrC(100)–W(100). This leads to stronger covalent bonds in ZrC(111)–W(110) than that in ZrC(100)–W(100). Therefore, we conclude that the stronger covalent and ionic forces in ZrC(111)–W(110) than those in ZrC(100)–W(100) are responsible for making ZrC(111)–W(110) to be the most stable interface. This study addresses the long-standing question of the most stable W–ZrC interface and derives a number of implications for other W-transition metal carbide interfaces which are potential candidates for improving the mechanical properties of plasma facing materials. [ABSTRACT FROM AUTHOR]

Sb is a three-dimensional Peierls insulator. The Peierls instability gives rise to doubling of the translational period along the [111] direction and alternating van der Waals and covalent bonding between (111) atomic planes. At the (111) surface of Sb, the Peierls condition is violated, which in theory can give rise to properties differing from the bulk. The atomic and electronic structure of the (111) surface of Sb have been simulated by density functional theory calculations. We have considered the two possible (111) surfaces, containing van der Waals dangling bonds or containing covalent dangling bonds. In the models, the surfaces are infinite and the structure is defect free. Structural optimization of the model containing covalent dangling bonds results in strong deformation, which is well described by a topological soliton within the Su–Schrieffer–Heeger model centered about 25 Å below the surface. The electronic states associated with the soliton see an increase in the density of states (DOS) at the Fermi level by around an order of magnitude at the soliton center. Scanning tunneling microscopy and spectroscopy (STM/STS) measurements reveal two distinct surface regions, indicating that there are different surface regions cleaving van der Waals and covalent bonds. The DFT is in good agreement with the STM/STS experiments. [ABSTRACT FROM AUTHOR]

Density functional theory in the local spin density approximation is used to investigate the structural, electronic, and magnetic properties of PbRuO3 under hydrostatic pressure. The calculated results show that under hydrostatic pressure, the ground state of Pm 3 ¯ m PbRuO3 is a ferromagnetic metal. The covalent bond of Pb–O strengthens as hydrostatic pressure increases, the exchange splitting of up- and down-spin channels of Ru 4d t2g weakens, and the magnetic properties decrease. The calculated ground state of Pbnm PbRuO3 is a paramagnetic metal, which is consistent with the experimental results at P = 0 GPa. The ground state of Imma PbRuO3 has weak ferromagnetism, which is close to the experimental results at P = 0 GPa. The Pbnm–Imma phase transition occurs when passing the critical hydrostatic pressure. The main reason is the distortion of Pb2+ at the A-site, which changed the bond length of Pb–O and the covalent strength of Pb–O, affecting the electron occupation of Ru 4d and leading to the Pbnm–Imma phase transition. [ABSTRACT FROM AUTHOR]

Based on first-principles density functional theory calculations and chemical bond analyses, we attempted to study the formation of oxygen vacancies (V O ) in strained Ti-based oxides. Structural features (e.g., cell volume and mean Ti–O bond length) exhibit a clear and linear correlation with strain. Further, electronic features (e.g., bandgap and Ti–O covalent bond strength) exhibit similar trends for hydrostatic, biaxial, and uniaxial strains, except for shear strains. We investigated the impact of strain on the formation of V O and found that the formation energy in strained oxides was almost linearly linked to changes in the cell volume, bandgap, and Ti–O bond strength of the host oxide, where V O were formed. However, these correlations are not valid in compressively strained systems, which include Ti–O bonds—the bond length being shorter than the sum of Ti and O ionic radii, and shear-strained systems. [ABSTRACT FROM AUTHOR]

Bimetallic sandwich complexes based on the borazocine (B4N4H8) ligand have been studied using density functional theory (DFT). The studied Ca–Ca covalent bond length agrees well with the experimental Ca2 bond length. For the studied complexes, the non-nuclear attractor (NNA) is found at the Ca–Ca bond of K2(B4N4H8)2Ca2 and Na2(B4N4H8)2Ca2. The negative Laplacian at the NNA is noticed for these two complexes, indicating that these complexes are electrides. This study for the first time reports the electride complexes based on the B4N4H8 ligand. Interestingly, upon asymmetric doping with Na and K, no NNA point is found for the complex NaK(B4N4H8)2Ca2, indicating that this complex is not an electride. Our study points out one of the fascinating outcomes that asymmetric doping can affect the occurrence of the NNA in a system. The complex Na2(B4N4H8)2Ca2 exhibits the highest second hyperpolarizability value of 2.2 × 106 au at the ωB97XD/6-311++G(3df,3pd) level among the studied sandwich complexes. [ABSTRACT FROM AUTHOR]

With hydrogen contents 6.69 and 7.49 wt%, Sn(AlH 4) 4 and Zr(AlH 4) 4 were experimentally synthesized, but their structures, bonding natures and hydrogen storage properties were not further investigated. This paper determines the low energy structures of Sn(AlH 4) 4 and Zr(AlH 4) 4 crystals by using global optimization algorithm combined with density functional theories, and analyze their electronic structures and bonding properties. The most stable structures of Sn(AlH 4) 4 and Zr(AlH 4) 4 contain isolated H 2 molecules. The formation enthalpies of Zr(AlH 4) 4 reaches 1.0 eV and the value of Sn(AlH 4) 4 is a little smaller. In Zr(AlH 4) 4 , the AlH 5 , AlH 6 and Al 2 H 6 units are connected tightly by Zr atoms through H bridges. In Sn(AlH 4) 4 , the AlH 6 units form a net structure, and the Sn atom exists in SnH 3 with one shared H atom. The bonding characteristics are analyzed by calculating charge populations and crystal orbital hamilton population (COHP). The metal components (Al, Sn, Zr) and H atoms form polarized covalent bonds. The covalent contributions are close for Sn–H and Al–H bonds but the charge values on the Sn atoms are much smaller. For the Zr–H bonds, both the charges on the Zr atoms and the covalent contributions are smaller than the values of the Al–H bonds. Combining the bonding natures and the structure features, it suggests that proper electronegativity of the metal atoms (Sn and Zr here) is the key factor for the stabilities and reversible hydrogen storage properties of metal aluminum hydrides. • The crystal phases of Sn(AlH 4) 4 and Zr(AlH 4) 4 are predicted. • The metal components (Al, Sn, Zr) and H atoms form polarized covalent bonds. • In Zr(AlH 4) 4 , Polarized covalent Zr–H bond is weaker than Al–H bond. • Hydrogen storage capacity in Sn(AlH 4) 4 and Zr(AlH 4) 4 reaches 6.69 and 7.49 wt%,respectively. • The electronegativity of metal atoms in aluminum hydrides is related to structural stability and reversible hydrogen storage. [ABSTRACT FROM AUTHOR]

The protection of implant surfaces from biofilm and corrosion is crucial for osteogenesis and tissue engineering. To this end, an L-glutamine-based green corrosion inhibitor with recently established anticancer properties has been applied onto antibacterial Cu(111) surfaces that usually cover the Ti-based implants. Among several configurations, L-glutamine prefers the parallel to the surface orientation with the carbon chain along the [110] direction having the heteroatoms N and O atoms on top of Cu surface atoms, which is important for the creation of a planar two-dimensioned (2d) stable coating. L-glutamine forms well-localized, directional covalent-like bonded states (below −3 eV) with the Cu surface atoms, using mainly its backbone's N1 atom that interestingly also shows electron charge occupation in the single-molecule highest occupied state, denoting its ability as an active center. The Mulliken analysis shows charge transfer from the molecule's N, C and Cu neighboring atoms towards the O atoms revealing the strong bond tendency of L-glutamine and therefore its ability to act as a corrosion inhibitor on the Cu surface. Additional L-glutamine adsorption results in intermolecular covalent bonding between the molecules, proving the ability of this amino acid to form a stable protective 2d organic coating on Cu(111). These results could be used for the design of a multifunctional hybrid (organic–metallic) coating with anticorrosion, anticancer and antibacterial properties suitable for many technological applications. [ABSTRACT FROM AUTHOR]

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. Here, we employed a self-consistent hybrid functional where the Hartree–Fock mixing parameter is self-consistently determined and thus the empiricism of the hybrid functional is effectively removed to calculate the bandgaps of various nitride compounds. By comparing the bandgaps from the self-consistent hybrid functional calculations with the available experimental and high-level GW calculation results, we found that the self-consistent hybrid functional can provide a computationally efficient approach for quantitative predictions of nitride electronic structures with an accuracy level comparable to the GW method. Additionally, we aligned the band edge positions of various nitride compounds using self-consistent hybrid functional calculations, providing material design principles for heterostructures of nitride-based optoelectronic devices. We anticipate the wide use of the self-consistent hybrid functional for accelerating explorations and predictions of new nitride-based functional materials in various photoactive applications. [ABSTRACT FROM AUTHOR]

The surfaces of waimirite β‐YF3have been studied for their fluorine and chlorine versus water affinity. Bonding patterns of HF, HCl, and H2O chemically adsorbed onto surfaces of (010), (100), (011), and (101) have been quantified by density functional theory applying energy decomposition analysis. We found that the adsorption of H2O is dominated by about 65% of electrostatics, which causes a low surface sensitivity and weak interactions. On the contrary, the adsorptions of HF and HCl are driven by strong hydrogen bonds resulting in a highly surface‐dependent ratio of 30–60% electrostatic versus orbital contribution. Among the stoichiometric surfaces, the shortest and strongest hydrogen bonds and consequently most covalent bonding patterns are found within YF3·HCl. However, when including the preparation energy, each surface favors the adsorption of HF over HCl, which reproduces the higher affinity of yttrium towards fluoride over chloride, previously known for solutions, also for the solid state. [ABSTRACT FROM AUTHOR]

Objective: Design a new cross‐linked polyethylene (XLPE) insulation material without cross‐linking by‐products (an alternative to peroxide cross‐linking). Investigate the process of covalent bonds forming and reaction mechanism of four reaction systems. Method: Theoretical calculation of the reaction potential energy information of the eleven reaction channels is used density functional theory at B3LYP/6‐311+G(d,p) level. Results: The calculation results show that the epoxy and reactive functional groups between two poly‐ethylene copolymers can react in situ, form covalent bonds, and realize a network XLPE. This reaction process is cross‐linking byproduct‐free. The reactivity of carboxylic acid functional group is stronger among four reaction systems considered. Discussion: The reaction Gibbs energy barriers of synergistic reaction are lower than that of step by step reaction. The reaction channel of attacking tertiary carbon site CH on epoxy is more kinetically favorable than that of attacking secondary carbon site CH2 on epoxy. Conclusion: The cross‐linking of epoxy and reactive functional groups between two polyethylene copolymers in situ would be beneficial to avoid forming cross‐linking byproducts of peroxide cross‐linking process, which is a promising method for design thermoplastic insulation materials for power cables. [ABSTRACT FROM AUTHOR]

The potential application of borophene as a sensing material for gas-sensing devices is investigated in this work. We utilize density functional theory (DFT) to systematically study the adsorption mechanism and sensing performance of χ3-borophene to search for high-sensitivity sensors for minor pollutant gases. We compare the results to those for two Pmmn borophenes. The first-principles calculations are used to analyze the sensing performance of the three different borophenes (2 Pmmn borophene, 8 Pmmn borophene, and χ3-borophene) on five leading harmful gases (CO, NH3, SO2, H2S, and NO2). The adsorption configuration, adsorption energy, and electronic properties of χ3-borophene are investigated. Our results indicate that the mechanism of adsorption on χ3-borophene is chemisorption for NO2 and physisorption for SO2 and H2S. The mode of adsorption of CO and NH3 on χ3-borophene can be both physisorption and chemisorption, depending on the initially selected sites. Analyses of the charge transfer and density of states show that χ3-borophene is selective toward the adsorption of harmful gases and that N and O atoms form covalent bonds when chemisorbed on the surface of χ3-borophene. An interesting phenomenon is that when 8 Pmmn borophene adsorbs SO2, the gas molecules are dismembered and strongly adsorb on the surface of 8 Pmmn borophene, which provides a way of generating O2 while adsorbing harmful substances. Overall, the results of this work demonstrate the potential applications of borophene as a sensing material for harmful gas sensing or removal. [ABSTRACT FROM AUTHOR]

This work determines the phase stabilities and point defect energetics of TiSi2 and TiGe2 allotropes using density functional theory. The primary focus is on the C49 and C54 allotropes, which compete during TiSi2 phase formation. It is found that the ground state structure for TiGe2 is the C54 allotrope, desirable for its low sheet resistance, while the less desirable, higher resistance C49 allotrope forms the ground state structure of TiSi2. A first attempt to understand the Ge atom's role in lowering the enthalpy of formation for the C54 structure is made from the perspective of the extended Born model. Charge density differences, the density of states, and Bader charge analysis show that these systems are predominantly ionically bonded, with the Ge atoms introducing additional covalent bond stability for the C54 allotrope. It is known that higher temperatures favor C54 formation in TiSi2. Helmholtz free energy calculations for TiSi2 suggest that the vibrational free energy does not drive the system to the C54 phase. The formation energies of certain point defects within the C49 structure of TiSi2 are less than 1 eV, which is consistent with experiments that show high defect concentrations. Thus, the driving force for C54 formation at higher temperatures may be related to the high defect concentration in the C49 allotrope. [ABSTRACT FROM AUTHOR]

Molecular adsorption at organic/metal interfaces depends on a range of mechanisms: covalent bonds, charge transfer, Pauli repulsion, and van der Waals (vdW) interactions shape the potential energy surface (PES), making it key to understanding organic/metal interfaces. Describing such interfaces with density functional theory requires carefully selecting the exchange correlation (XC) functional and vdW correction scheme. To explore the reproducibility of the PES with respect to the choice of method, we present a benchmark of common local, semi-local, and non-local XC functionals in combination with various vdW corrections. We benchmark these methods using perylene-tetracarboxylic dianhydride on Ag(111), one of the most frequently studied organic/metal interfaces. For each method, we determine the PES using a Gaussian process regression algorithm, which requires only about 50 density functional theory calculations as input. This allows a detailed analysis of the PESs' features, such as the positions and energies of minima and saddle points. Comparing the results from different combinations of XC functionals and vdW corrections enables us to identify trends and differences between the approaches. PESs for different computation methods are in qualitative agreement but also display significant quantitative differences. In particular, the lateral positions of adsorption geometries agree well with experiment, while adsorption heights, energies, and barriers show larger discrepancies. [ABSTRACT FROM AUTHOR]

Practical ways to calculate the tunneling matrix elements and analyze the tunneling pathways for protein electron-transfer (ET) reactions with a fragment molecular orbital (FMO) method are presented. The straightforward use of minimal basis sets only for the atoms involved in the covalent bond detachment in FMO can properly describe the ETs through the protein main-chains with the cost-effective two-body corrections (FMO2) without losing the quality of double-zeta basis sets. The current FMO codes have been interfaced with density functional theory, polarizable continuum model, and model core potentials, with which the FMO-based protein ET calculations can consider the effects of electron correlation, solvation, and transition-metal redox centers. The reasonable performance of the FMO-based ET calculations is demonstrated for three different sets of protein-ET model molecules: (1) hole transfer between two tryptophans covalently bridged by a polyalanine linker in the ideal α-helix and β-strand conformations, (2) ET between two plastoquinones covalently bridged by a polyalanine linker in the ideal α-helix and β-strand conformations, and (3) hole transfer between ruthenium (Ru) and copper (Cu) complexes covalently bridged by a stretch of a polyglycine linker as a model for Ru-modified derivatives of azurin. [ABSTRACT FROM AUTHOR]

Tin selenide (SnSe) is a layered semiconductor, which is reported to be the best thermoelectric material to date. Few-layer tin selenide is highly sensitive to external conditions such as strain, pressure, or temperature. Crystal structure of SnSe is orthorhombic, where atoms are arranged in an accordionlike structure with nonbonding intralayer interactions. Bulk and few-layer pristine SnSe are reported to have indirect electron bandgaps. Based on the results from first-principles density functional theory calculations, we show that two major structural changes can happen upon substitutional chemical doping of bilayer SnSe. Substitutional chemical doping can manipulate the directionality of interlayer interactions of bilayer SnSe, which results in an indirect-direct transition of the electronic bandgap. Our results also suggest that larger dopant atoms can convert the nonbonding intralayer interactions to covalent bonding. Such an increase in the atomic orbital overlap may result in a semiconductor-semimetal transition. [ABSTRACT FROM AUTHOR]

By the first-principle calculation method based on density functional theory, the adsorption processes of sulfur (S) doped, selenium (Se) doped and sulfur-selenium co-doped diamond substrates with different active groups were studied. The adsorption energy, Mulliken charge distribution and chemical bond overlap number of three different substrates with different hydrocarbon groups (C, CH, CH2, CH3 ) in the deposition atmosphere were calculated and analyzed. The results show that the covalent bonds between the sulfur doped model and C, CH and CH2 groups, the selenium doped model and C and CH groups, the sulfur and selenium co-doped model and C, CH and CH2 are formed through charge transferring. The bonds between sulfur doped model and CH group, and between sulfur and selenium co-doped model and C group are very close to the C—C bond of the ideal diamond. The addition of sulfur and selenium can add more growth active sites on the basis of the original diamond grain homoepitaxial growth. [ABSTRACT FROM AUTHOR]

The development of highly active and durable platinum‐free oxygen reduction reaction (ORR) catalysts is of vital importance for the practical application of anion‐exchange membrane fuel cells (AEMFCs). Herein, a metal‐free carbon catalyst (marked as NDPC‐1000) with a graphitic N‐regulating defect structure is specifically designed and developed for AEMFCs by integrating theoretical calculations and experiments. Density functional theory calculations first reveal that the graphitic N can tailor the charge density of pentagon and armchair defects to reach the top of the adsorption energy‐activity volcano plot, while the enhanced durability is attributed to the high dissociation energy of the CN covalent bond. Under this guidance, the synthesized NDPC‐1000 demonstrates its high ORR activity and durability in alkaline media. With H2/O2 reacting gases, the AEMFC with this catalyst as the cathode delivers a peak power density of 913 mW cm−2. Unprecedented fuel cell durability is verified via continuous operation over 100 h at 0.25 A cm−2 with only a voltage decay of ≈25%, which is the greatest among all reported metal‐free‐based AEMFCs. Here a theory‐guided experiment strategy is provided for the development of high‐performance and durable ORR catalysts for AEMFCs. [ABSTRACT FROM AUTHOR]

Bilayer compounds of two-dimensional T12 phase carbon allotrope and penta-graphene have been studied using the electron density functional theory. The stability of the considered two-dimensional structures with different types of stacking order at different temperatures has been estimated from the calculated phonon spectra and molecular dynamics simulation. The stability of the two-dimensional planar structure up to 1350 K has been demonstrated. It has been shown that bilayer penta-graphene compounds with the AA' and AB' stacking orders have energy minima both in the state with the van der Waals interaction and in the form of covalently bonded layers in the AA-T12 and T12 phases. The barrier for the transition between covalently and van der Waals bonded AA' and AB' stacking orders has been analyzed. The calculated electronic and optical characteristics show that the band gap in the case of covalent bonding is much narrower than that in the case of van der Waals bonding. [ABSTRACT FROM AUTHOR]

The fundamental understanding and precise control of catalytic sites are challenging yet essential to explore advanced electrocatalysts for the formic acid oxidation reaction (FAOR). Herein, this work demonstrates a new and promising catalyst prototype of antiperovskite‐type PdFe3N which possesses ordered and isolated Pd sites. The as‐synthesized PdFe3N/N‐rGO exhibits significant enhancement in catalytic activity, robust stability, and Fe anti‐dissolution properties when compared with PdFe3/rGO and Pd/C. Density functional theory (DFT) calculations reveal that isolated and ordered Pd sites are beneficial for high formate coverage and thus suppressing CO formation/poisoning. Moreover, the strong Fe–N covalent bonds improve the vacancy formation energy of Fe, which ensures superior Fe anti‐dissolution properties. Beyond offering a promising candidate for catalyzing FAOR, these findings provide deeper insights into the structure of CO tolerance relationships and benefit the theory‐guided design of highly efficient catalysts. [ABSTRACT FROM AUTHOR]

Efforts to fabricate high-conducting and high-strength free-standing graphene/carbon nanotube (CNT) buckypaper through room-temperature functionalization have been frustrated by the defective surface of the graphene and CNTs. In this study, high-quality graphene sheets were prepared via an amino-assisted liquid phase exfoliation method and used to integrate with CNTs to form free-standing flexible graphene/CNTs buckypaper. After that, individual graphene and CNT of the graphene/CNTs buckypaper were linked via diazonium chemistry to generate covalent bonds. By tuning functionalization time, the functionalized graphene/CNTs buckypaper exhibits an electrical conductivity of 87,500 S/m and a Young's modulus of 22.3 GPa, which are 6 and 10 times higher, respectively, than unfunctionalized graphene/CNTs buckypaper. Density functional theory calculations demonstrate that charge transfer rate (K et) of the aryl linker bonded moiety configuration via covalent functionalization is an order faster than without the aryl linker bonded moiety configuration. Unprecedently, the capacitance of the functionalized graphene/CNTs buckypaper is 359.6 mF/cm3 at a scan rate of 1 mV/s with no capacitance change after 10,000 cycles of testing. This work sheds the light of the value of molecular engineering in the design of novel composite for flexible electronics, energy storage and provides important insights into the understanding of basic principles of covalent functionalization of graphene/CNTs. The functionalized graphene/CNTs buckypaper were crosslinked to form covalent bonds between individual material via diazonium chemistry reaction and it achieved an electrical conductivity of 875 S/cm and Young's modulus of 22.3 GPa, which are 6 and 10 times higher than unfunctionalized graphene/CNTs buckypaper. Besides, charge transfer rate (K et) of the functionalized graphene/CNTs shows ten times faster than unfunctionalized moiety configuration. [Display omitted] [ABSTRACT FROM AUTHOR]

The Mg 17 Al 12 -phase, which is common and important in Mg-Al alloy, has long been regarded as a brittle phase in experiments but theoretical calculations report controversial results. To unravel why theoretical calculations report controversial results and determine whether Mg 17 Al 12 is brittle or ductile, density functional theory calculations on atomic level are performed to investigate mechanic properties of Mg 17 Al 12 without containing alloying elements and without taking the size effect. The results showed that the parameter k -point played critical role in the DFT-based elastic calculations. The convergent G/B ratio of Mg 17 Al 12 was about 0.52, suggesting that the Mg 17 Al 12 -phase was theoretically ductile although its ductility was poor. The chemical bonding in Mg 17 Al 12 was the mixture of metallic Mg-Mg bond and covalent Al-Al bond. The advantage of metallic bonding over covalent bonding provided a possible explanation for the ductility of Mg 17 Al 12. Possible reasons for the brittleness of Mg 17 Al 12 in experiments are also discussed. [ABSTRACT FROM AUTHOR]

An organoboron small-molecular acceptor (OSMA) MB←N containing a boron–nitrogen coordination bond (B←N) exhibits good light absorption in organic solar cells (OSCs). In this work, based on MB←N, OSMA MB-N, with the incorporation of a boron–nitrogen covalent bond (B-N), was designed. We have systematically investigated the charge-transport properties and interfacial charge-transfer characteristics of MB-N, along with MB←N, using the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT). Theoretical calculations show that MB-N can simultaneously boost the open-circuit voltage (from 0.78 V to 0.85 V) and the short-circuit current due to its high-lying lowest unoccupied molecular orbital and the reduced energy gap. Moreover, its large dipole shortens stacking and greatly enhances electron mobility by up to 5.91 × 10−3 cm2·V−1·s−1. Notably, the excellent interfacial properties of PTB7-Th/MB-N, owing to more charge transfer states generated through the direct excitation process and the intermolecular electric field mechanism, are expected to improve OSCs performance. Together with the excellent properties of MB-N, we demonstrate a new OSMA and develop a new organoboron building block with B-N units. The computations also shed light on the structure–property relationships and provide in-depth theoretical guidance for the application of organoboron photovoltaic materials. [ABSTRACT FROM AUTHOR]

Li metal anode holds great promise to realize high‐energy battery systems. However, the safety issue and limited lifetime caused by the uncontrollable growth of Li dendrites hinder its commercial application. Herein, an interlayer‐bridged 3D lithiophilic rGO‐Ag‐S‐CNT composite is proposed to guide uniform and stable Li plating/stripping. The 3D lithiophilic rGO‐Ag‐S‐CNT host is fabricated by incorporating Ag‐modified reduced graphene oxide (rGO) with S‐doped carbon nanotube (CNT), where the rGO and CNT are closely connected via robust Ag‐S covalent bond. This strong Ag‐S bond could enhance the structural stability and electrical connection between rGO and CNT, significantly improving the electrochemical kinetics and uniformity of current distribution. Moreover, density functional theory calculation indicates that the introduction of Ag‐S bond could further boost the binding energy between Ag and Li, which promotes homogeneous Li nucleation and growth. Consequently, the rGO‐Ag‐S‐CNT‐based anode achieves a lower overpotential (7.3 mV at 0.5 mA cm−2), higher Coulombic efficiency (98.1% at 0.5 mA cm−2), and superior long cycling performance (over 500 cycles at 2 mA cm−2) as compared with the rGO‐Ag‐CNT‐ and rGO‐CNT‐based anodes. This work provides a universal avenue and guidance to build a robust Li metal host via constructing a strong covalent bond, effectively suppressing the Li dendrites growth to prompt the development of Li metal battery. [ABSTRACT FROM AUTHOR]

We present a non-decomposable approximation for the non-additive non-interacting kinetic energy (NAKE) for covalent bonds based on the exact behavior of the von Weizsäcker (vW) functional in regions dominated by one orbital. This covalent approximation (CA) seamlessly combines the vW and the Thomas-Fermi functional with a switching function of the fragment densities constructed to satisfy exact constraints. It also makes use of ensembles and fractionally occupied spin-orbitals to yield highly accurate NAKE for stretched bonds while outperforming other standard NAKE approximations near equilibrium bond lengths. We tested the CA within Partition-Density Functional Theory (P-DFT) and demonstrated its potential to enable fast and accurate P-DFT calculations. [ABSTRACT FROM AUTHOR]

Highlights: The adsorption models of RGD on different surfaces of Mg and Mg alloys were set up. Alloying elements promoted the adsorption of RGD on different Mg surfaces. The ligand covalent bond between RGD and substrate was formed. The pronounced localization of electrons of Mg(11 2 ¯ 0) and Mg(10 1 ¯ 1) surfaces improved the adsorption. Functional Arg-Gly-Asp (RGD) tripeptide has a tremendous potential in clinical applications to accelerate the endothelialization of Magnesium (Mg) alloy vascular stent surface. The interaction mechanism of RGD on different surfaces of Mg and Mg alloy is important for promoting the development of Mg alloy vascular stent, yet still unclear. In the present work, first-principles calculation within density functional theory (DFT) was performed to investigate the interaction mechanism. The electron redistribution, effect of alloying elements and changes in the density of states of the adsorption systems were studied. The results revealed that RGD interacted with different surfaces of Mg (0001), Mg(11 2 ¯ 0) and Mg(10 1 ¯ 1) through ligand covalent bond; the pronounced localization of electrons of Mg(11 2 ¯ 0) and Mg(10 1 ¯ 1) surfaces promoted the adsorption of RGD tripeptide compared with that on the Mg(0001) surface; Zn/Y/Nd alloying elements improved the adsorption of RGD. Calculated results could provide insight for the interaction mechanism of biomolecule on the Mg and Mg-based alloy surfaces, and point out some directions for the future experimental efforts. [ABSTRACT FROM AUTHOR]

Qualitative differences in the reactivity of trivalent lanthanide and actinide complexes have long been attributed to differences in covalent metal‐ligand bonding, but there are few examples where thermodynamic aspects of this relationship have been quantified, especially with U3+ and in the absence of competing variables. Here we report a series of dimeric phosphinodiboranate complexes with trivalent f‐metals that show how shorter‐than‐expected U−B distances indicative of increased covalency give rise to measurable differences in solution deoligomerization reactivity when compared to isostructural complexes with similarly sized lanthanides. These results, which are in excellent agreement with supporting DFT and QTAIM calculations, afford rare experimental evidence concerning the measured effect of variations in metal‐ligand covalency on the reactivity of trivalent uranium and lanthanide complexes. [ABSTRACT FROM AUTHOR]

Non‐metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. These properties mainly rely on maximizing the number of strong covalent bonds, with crosslinked XN6 octahedra frameworks being particularly attractive. In this study, the phosphorus–nitrogen system was studied up to 137 GPa in laser‐heated diamond anvil cells, and three previously unobserved phases were synthesized and characterized by single‐crystal X‐ray diffraction, Raman spectroscopy measurements and density functional theory calculations. δ‐P3N5 and PN2 were found to form at 72 and 134 GPa, respectively, and both feature dense 3D networks of the so far elusive PN6 units. The two compounds are ultra‐incompressible, having a bulk modulus of K0=322 GPa for δ‐P3N5 and 339 GPa for PN2. Upon decompression below 7 GPa, δ‐P3N5 undergoes a transformation into a novel α′‐P3N5 solid, stable at ambient conditions, that has a unique structure type based on PN4 tetrahedra. The formation of α′‐P3N5 underlines that a phase space otherwise inaccessible can be explored through materials formed under high pressure. [ABSTRACT FROM AUTHOR]

Non‐metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. These properties mainly rely on maximizing the number of strong covalent bonds, with crosslinked XN6 octahedra frameworks being particularly attractive. In this study, the phosphorus–nitrogen system was studied up to 137 GPa in laser‐heated diamond anvil cells, and three previously unobserved phases were synthesized and characterized by single‐crystal X‐ray diffraction, Raman spectroscopy measurements and density functional theory calculations. δ‐P3N5 and PN2 were found to form at 72 and 134 GPa, respectively, and both feature dense 3D networks of the so far elusive PN6 units. The two compounds are ultra‐incompressible, having a bulk modulus of K0=322 GPa for δ‐P3N5 and 339 GPa for PN2. Upon decompression below 7 GPa, δ‐P3N5 undergoes a transformation into a novel α′‐P3N5 solid, stable at ambient conditions, that has a unique structure type based on PN4 tetrahedra. The formation of α′‐P3N5 underlines that a phase space otherwise inaccessible can be explored through materials formed under high pressure. [ABSTRACT FROM AUTHOR]

The recent synthesis of single‐layer Janus‐type transition metal dichalcogenides (TMDs) raises the question of the existence of other possible 2D structures with an asymmetric out‐of‐plane structural configuration. In the present work, a theoretical search for new Janus structures having SMoSe and SVSe compositions is performed. A detailed crystal‐chemical analysis of the predicted structures is carried out, and it is shown that some of the dynamically stable structures are characterized by crystal‐chemical features that are unique among TMDs, including quadruple Mo—Mo bonds and covalent S—S and Se—Se bonds. It is also shown that Mo‐bearing TMDs have a tendency to form strong Mo—Mo bonds with chains or isolated dimers of molybdenum atoms, while in the case of vanadium‐containing TMDs this feature is not characteristic. Two predicted crystal structures, called 1M‐SVSe and 1A′‐SMoSe, are especially promising for experimental synthesis and practical applications owing to their dynamical stability and rather low value of enthalpy compared with known structures. The enthalpy of 1M‐SVSe is 0.22 eV per formula unit lower than that of 1T‐SVSe, while the enthalpy of 1A′‐SMoSe is 0.12 eV per formula unit lower than the enthalpy of 1T‐SMoSe. The performed topological analysis showed that the predicted structures are unique and do not have analogues in the Inorganic Crystal Structure Database. [ABSTRACT FROM AUTHOR]

[Display omitted] • Up to 97 % corrosion inhibition in 1 M HCl by new imidazolium ionic liquids. • Lower efficacy of nitro-substituted ILs in steel protection. • DFTB simulations validate ILs' covalent bonding with iron atoms. The persistent issue of carbon steel corrosion has led to extensive investigations, with ionic liquids emerging as a promising solution for mitigating this problem. This research assesses the corrosion inhibiting capabilities of four novel imidazolium ionic liquids (ILs), namely 1-benzyl-3-(2-nitrobenzoyl)-1H-imidazol-3-ium chloride (BNIC), 1-acetyl-3-(2-oxo-2-phenylethyl)-1H-imidazol-3-ium bromide (APIB), 1-acetyl-3-(2-(4-fluorophenyl)-2-oxoethyl)-1H-imidazol-3-ium bromide (AFIB), and 1-acetyl-3-(2-(4-chlorophenyl)-2-oxoethyl)-1H-imidazol-3-ium bromide (ACIB) for carbon steel in a 1.0 M acidic environment. A combination of experimental approaches, including electrochemical techniques, and theoretical Density Functional based Tight Binding (DFTB) modeling, were employed to evaluate the corrosion of carbon steel both with and without these inhibitors. The ILs demonstrated impressive inhibition efficiency, reaching up to 97 %. Notably, while most compounds offered significant protection, the Nitro-substituted IL exhibited the least effectiveness. The introduction of these compounds into the acidic solution significantly reduced the double layer capacitance and markedly increased the polarization resistance, indicating the adsorption of inhibitor molecules onto the metal surface. Density Functional Theory Based Tight Binding (DFTB) simulations supported these findings by confirming the establishment of covalent bonds between the inhibitor molecules and iron atoms. The study also reaffirmed the detrimental impact of nitro group substitution on the corrosion inhibition performance of corrosion inhibitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • D 8h symmetery of An(COT) 2 gets distorted after forming a complex with small molecules. • Electronic structures contribute to the attainment of the shortest An-C bond length. • An-Y bond is dominated by orbital attractions and shows significant covalence. The scarcity and radioactivity of actinides have made it very difficult to study actinocene and other actinide-containing complexes experimentally. Hence, theoretical studies of these complexes can offer significant direction in the enlightenment of difficult-to-obtain experimental data. Keeping in mind, actinocene (An(COT) 2 , An = Th, Pa, U, Np, Pu, Am, Cm) with D 8h symmetry has been investigated in the present study. Under D 8h symmetry, the structural parameters of optimized sandwich compounds are found to be in concurrence with the experimental data. This study extensively examines the experimentally characterized actinocene for their capability to activate small molecules (Y = CO, and N 2) through relativistic density functional theory (DFT) analysis. After forming a complex with CO, and N 2 , D 8h symmetry of An(COT) 2 gets distorted resulting in the bending of both the COT rings. In all the [An(COT) 2 Y] complexes, a covalent bond was realized between An and Y except [U(COT) 2 N 2 ], [Np(COT) 2 N 2 ], and [Pu(COT) 2 N 2 ], where an ionic bond was observed between An and Y. Furthermore, the experimental inaccessible [An(COT) 2 Y] complexes were elucidated through thermodynamic computations along with the analyses of geometric, electronic properties and bonding analysis. [Pu(COT) 2 N 2 ] adducts have the largest contribution of ΔE orb to total ΔE int among all the complexes suggesting that the Pu-N bond is dominated by orbital attractions and shows significant covalency. [ABSTRACT FROM AUTHOR]

• The ground state structure of MSn 9 − clusters (M = Sc , Y, La) is determined. • Ab initio molecular dynamics explain the thermal stability of the ScSn 9 − cluster. • Various bonding analyses are used to explain the reasons for stability. • The gauge-including magnetically induced currents visualizes the aromaticity. Doping rare earth elements into clusters can significantly improve the performance and application value of the materials. The structure, bonding properties, stability, and aromaticity of MSn 9 − (M = Sc , Y, La) have been investigated using density-functional theory. The global minimum structure of these clusters is determined to be the addition of a triangle to the vertex position of a pentagonal bipyramid. Ab initio molecular dynamics simulations are used to demonstrate the thermal stability of the structure. Bonding analyses indicate the presence of ionic bonding and covalent bonding. Iso-chemical shielding surfaces and the gauge-including magnetically induced currents indicate that MSn 9 − clusters are significantly aromatic. This study provides a comprehensive understanding of tin-based nanomaterials, which is important for their design and synthesis. Integrating AIMD simulations with diverse bonding analyses elucidates the stability of ScSn 9 − clusters, while revealing their aromaticity through visualization using GIMIC. [Display omitted] [ABSTRACT FROM AUTHOR]

Based on the first-principles calculations of density functional theory (DFT), the crystal structure, molecular structure, electronic properties, and optical absorption properties of methyl urotropine perchlorate under hydrostatic compression in the range of 0 ~ 100 GPa were calculated. The results show that the crystal structure of methyl urotropine perchlorate undergoes two structural transformations under hydrostatic compression. The H1A-H1B bond breaks at 25 GPa, generating two new covalent bonds N3-H1A and O1-H1B. The covalent bonds of O2A-C1 and Cl1-H3A are formed at 85 GPa. The compression ratio of lattice constants (a, b, c) and unit cell volume change abruptly at 25 GPa and 85 GPa, respectively. The conclusion that new bonds are formed under high pressure is further demonstrated by analyzing the partial density of states (PDOS) of N3, H1A, O1, H1B, O2A, C1, Cl1, and H3A atoms. The absorption spectrum showed that the absorption peak of methyl urotropine perchlorate gradually enhanced with the increase of pressure and the highest absorption peak shifted to high frequency. Highlights: The structure of methyl urotropine perchlorate was optimized, and its lattice constants (a, b, c, and V) and compression ratios at different pressures were calculated. Methyl urotropine perchlorate undergoes two structural transitions at pressurization to 25 GPa and 85 GPa, with the breaking of old bonds and the formation of new bonds. The DOS of methyl urotropine perchlorate was analyzed, further confirming the structural transformation by high pressure. The effect of high pressure on optical absorption properties was investigated. [ABSTRACT FROM AUTHOR]

Fe0.22V2O5(H2O)0.5 (FeVO) and Mn0.22V2O5(H2O)0.5 (MnVO) nanobelts with rich crystalline defects are synthesized by a facile one‐step hydrothermal approach. Their largest interlayer spacings are 10.6 Å and Rietveld refinement demonstrates the lamellar hydrated Fe3+ pillars in FeVO link different V–O–V layers via covalent bonds. Furthermore, all their V centers are five‐coordinated by O atoms, which is lower than the maximum coordination number of V (6), demonstrating that there are abundant oxygen vacancies (denoted as structural deficiency) in FeVO due to the lack of oxygen ligands, which can promote the migration of Zn2+ along the (001) surface of FeVO with a low energy barrier of 0.88 eV, as evidenced by density functional theory (DFT) simulations. FeVO exhibits an excellent capacity of 598 mAh g–1 at 0.1 A g–1 and long‐term cycling performance with a capacity retention of more than 80% over 1800 cycles at 5 A g–1, which is associated with the dual defects (structural oxygen vacancies and crystalline defects) and the extra capacity provided by the interconversion of Fe3+ ↔ Fe2+. Furthermore, a series of ex situ characterizations of the FeVO electrode reveal the co‐(de)intercalation of Zn2+/H+ and surface migration mechanism. [ABSTRACT FROM AUTHOR]

The excellent adhesion strength between the substrate and coating in the field of cemented carbide-coated tools is the crux of ensuring the durability of coated tools. The TiN coating is often used as a bonding layer to improve the bonding strength between the substrate and outer coating. Insights into detailed information on the interfacial properties between substrate and coating are essential for developing coating structures with optimal adhesion properties. Therefore, first-principles calculations were used to investigate the anisotropy of the elastic characteristics of WC and TiN as well as the bonding mechanism at the interface. The findings demonstrate that WC and TiN bulks have different symmetries in their anisotropy of elastic characteristics. WC(0001) and TiN(111) slabs can be well-lattice matched thanks to the low lattice mismatch ratio (2.7%). The HCP stacking mode has larger bonding energy than the OT and hole stacking modes in the interface structure with identical terminating atoms. The C-HCP-Ti interface forms covalent and ionic bonds, which is thermodynamically stable (γ = −1.127 J/m2) and has the highest bonding strength (Wad = 8.899 J/m2) among all interface structures. The results of this study provide a practical perspective for improving the mechanical properties of cemented carbide-coated tools. [ABSTRACT FROM AUTHOR]

The electronic structures of Zr 8 Co 8 and its hydrides have been systematically investigated using the first-principles calculation based on density functional theory. Additionally, the influence of the Ti and Hf doping on the atomic bonding properties of Zr 8 Co 8 and its hydrides (Zr 7 HfCo 8 , Zr 7 HfCo 8 H, Zr 16 Co 15 HfH 48 , Zr 7 TiCo 8 , Zr 7 TiCo 8 H, and Zr 16 Co 15 TiH 48 compounds) were also studied to provide new insights into the hydrogenation of Zr 8 Co 8. The Ti and Hf atoms were occupied the Zr position in the ZrCo alloy, while they were occupied the Co position in the Zr 16 Co 16 H 48 system. Ti and Hf doping could achieve the purpose of anti-disproportionation. Ti and Hf could weak the Zr–Co bond for the improvement of the hydrogenation performance of Zr 8 Co 8 , and the covalence of the Co–H bond was higher than that of the Zr–H bond. The existence of a Co–H covalent bond in the crystal is conducive to the hydrogen absorption of Zr 8 Co 8 to form Zr 16 Co 16 H 48. Inhibition of Co–H interaction during Zr 8 Co 8 hydrogenation can accelerate the formation of Zr 8 Co 8 H for the improvement of its hydrogenation performance. • The purpose of this article is to provide new insights into the hydrogenation of Zr 8 Co 8. • The Ti and Hf occupy the Zr position of ZrCo, while they occupy the Co position of ZrCo hydride. • Inhibition of Co–H interaction can improve hydrogenation performance of ZrCo. [ABSTRACT FROM AUTHOR]