Computational characterization of novel nanostructured materials: A case study of NiCl2

Alnemrat S., Tomlinson W.W.

Ab initio calculations are used to study the properties of two dimensional (2D) Transition Metal Halides (TMH, TM=Ni; H = Cl, Br) encapsulated inside a derivative of UiO-67 Metal-Organic Frameworks (MOF). Two monolayers of TMHs (NiCl2 and NiBr2) were isolated from the experimental Crystallographic Information File (CIF) and used in this study. We found that the structure of both monolayers within the MOF ([email protected]) have very similar geometries compared to their perfect 2D sheets hypothetically derived from their bulk structures ([email protected]) with small distortions in the Metal–Metal (M–M) and Metal–Halide (M–H) bonds. NiCl2 and NiBr2 sheets have a Ferromagnetic (FM) ground state with large intrinsic magnetic moments localized at each metal site. The predicted FM ground state is also confirmed in the magnetic exchange coupling constant (J) calculations between M centers which are found all positive, but non isotropic within each sheet. Weaker interactions with J ≈0.2 meV are found among NN centers in the outer ring compared to J ≈0.85 meV in the inner rings of both monolayers. The calculated Jś are inserted in a Monte Carlo (MC) code to afford Curie temperatures of 27 K and 22 K for NiCl2/Br2 monolayers respectively. Finally, the experimentally collected structures at low metal loading were found to have distinct magnetic properties compared to the completely filled sheets.

Pedone A., Bertani M., Brugnoli L., Pallini A.

The continuous development and improvement of interatomic potential models for oxide glasses have made classical molecular dynamics a powerful computational technique routinely used for studying the structure and properties of such materials on a par with the more advanced experimental techniques. In this brief review, we retrace the development of the most used interatomic potential models from the earliest MD simulations up to now with a look at the possible future developments in this field due to the advent of the machine learning era and data-driven methods. • An historical overview of the interatomic potentials models for oxide glasses is provided. • The applicability and accuracy of the developed models are discussed. • Practical considerations for optimizing interatomic potential parameters are reported. • Future perspectives on the development of Machine Learning Force-Fields are discussed.

Kistanov A.A., Shcherbinin S.A., Botella R., Davletshin A., Cao W.

A large number of novel two-dimensional (2D) materials are constantly discovered and deposed into the databases. Consolidate implementation of machine learning algorithms and density functional theory (DFT) based predictions have allowed creating several databases containing an unimaginable amount of 2D samples. The next step in this chain, the investigation leads to a comprehensive study of the functionality of the invented materials. In this work, a family of transition metal dichlorides has been screened out for systematical investigation of their structural stability, fundamental properties, structural defects, and environmental stability via DFT based calculations. The work highlights the importance of using the potential of the invented materials and proposes a comprehensive characterization of a new family of 2D materials.

Zhang B., Zhang L., Yang N., Zhao X., Chen C., Cheng Y., Rasheed I., Ma L., Zhang J.

Zhou D., Cui K., Zhou Z., Liu C., Zhao W., Li P., Qu X.

High dehydrogenation temperature and slow dehydrogenation kinetics impede the practical application of magnesium hydride (MgH 2 ) serving as a potential hydrogen storage medium. In this paper, Fe–Ni catalyst modified three-dimensional graphene was added to MgH 2 by ball milling to optimize the hydrogen storage performance, the impacts and mechanisms of which are systematically investigated based on the thermodynamic and kinetic analysis. The MgH 2 +10 wt%Fe–Ni@3DG composite system can absorb 6.35 wt% within 100 s (300 °C, 50 atm H 2 pressure) and release 5.13 wt% within 500 s (300 °C, 0.5 atm H 2 pressure). In addition, it can absorb 6.5 wt% and release 5.7 wt% within 10 min during 7 cycles, exhibiting excellent cycle stability without degradation. The absorption-desorption mechanism of MgH 2 can be changed by the synergistic effects of the two catalyst materials, which significantly promotes the improvement of kinetic performance of dehydrogenation process and reduces the hydrogen desorption temperature. • Synergistic effects of graphene and iron based catalysts have been investigated. • Remarkable features revealed via XRD, SEM, EDS, HRTEM, PCT and DSC. • The conversion of Mg 2 Ni and Mg 2 NiH 4 enhances the performance of hydride storage. • The MgH 2 -10 wt% Fe–Ni @3DG sample releases 5.13 wt% H 2 within 500 s at 300 °C.

Bykov M., Bykova E., Ponomareva A.V., Tasnádi F., Chariton S., Prakapenka V.B., Glazyrin K., Smith J.S., Mahmood M.F., Abrikosov I.A., Goncharov A.F.

Most of the studied two-dimensional (2D) materials are based on highly symmetric hexagonal structural motifs. In contrast, lower-symmetry structures may have exciting anisotropic properties leading to various applications in nanoelectronics. In this work we report the synthesis of nickel diazenide NiN2 which possesses atomic-thick layers comprised of Ni2N3 pentagons forming Cairo-type tessellation. The layers of NiN2 are weakly bonded with the calculated exfoliation energy of 0.72 J/m2, which is just slightly larger than that of graphene. The compound crystallizes in the space group of the ideal Cairo tiling (P4/mbm) and possesses significant anisotropy of elastic properties. The single-layer NiN2 is a direct-band-gap semiconductor, while the bulk material is metallic. This indicates the promise of NiN2 to be a precursor of a pentagonal 2D material with a tunable direct band gap.

Safina L.R., Krylova K.A., Murzaev R.T., Baimova J.A., Mulyukov R.R.

Understanding the structural behavior of graphene flake, which is the structural unit of bulk crumpled graphene, is of high importance, especially when it is in contact with the other types of atoms. In the present work, crumpled graphene is considered as storage media for two types of nanoclusters—nickel and hydrogen. Crumpled graphene consists of crumpled graphene flakes bonded by weak van der Waals forces and can be considered an excellent container for different atoms. Molecular dynamics simulation is used to study the behavior of the graphene flake filled with the nickel nanocluster or hydrogen molecules. The simulation results reveal that graphene flake can be considered a perfect container for metal nanocluster since graphene can easily cover it. Hydrogen molecules can be stored on graphene flake at 77 K, however, the amount of hydrogen is low. Thus, additional treatment is required to increase the amount of stored hydrogen. Remarkably, the size dependence of the structural behavior of the graphene flake filled with both nickel and hydrogen atoms is found. The size of the filling cluster should be chosen in comparison with the specific surface area of graphene flake.

Deng P., Nie X., Wu Y., Tian Y., Li J., He Q.

Preparation of the Ni NPs/N-C nanohybrid and construction processes of the proposed Ni NPs/N-C/CPE-based electrochemical Trp sensor. • Cost-saving preparation of Ni NPs/N-C was simply prepared as advanced electrode materials. • Electrochemical sensor for tryptophan detection by Ni NPs/N-C/CPE was fabricated. • The sensor shows high electrochemical performance and good sensitivity for Trp. • Low-cost, high stability and repeatability of Ni NPs/N-C/CPE were witnessed. Here we report a facile and cost-effective preparation of nickel nanoparticle S/Nitrogen-carbon nanohybrid (Ni NPS/N-C) based on formamide condensation and carbonization, used for highly sensitive and selective electrochemical determination of tryptophan (Trp) in practical samples. The crystallographic phase, surface morphology, elemental distribution, and chemical state of the Ni NPS/N-C nanohybrid were analyzed by XRD, SEM, TEM, EDS, XPS, FTIR, TGA and Raman spectra. The results show that high content of Ni NPs (6.62 wt%) were distributed in the nanohybrid, and a large number of bamboo-like nanotubes were formed during pyrolysis, which dramatically increases the specific surface area, and remarkably promotes the electrical conductivity as well as the catalytic activity of the nanohybrid. The electrochemical behavior of Trp was investigated on the nanohybrid modified carbon paste electrode (Ni NPS/N-C/CPE) and the measurement parameters were optimized. As expected, the modified electrode can remarkably enhance the electrochemical oxidation signal of Trp. Under the optimal experimental conditions, a linear relationship in the range of 0.01–20 μM and 20–80 μM for Trp was established with detection limit of 5.7 nM (S/N = 3). Finally, the proposed sensor was practically applied by evaluation and determination of Trp from various sourcing samples including human serum and pharmaceutical samples.

de Vera P., Azzolini M., Sushko G., Abril I., Garcia-Molina R., Dapor M., Solov’yov I.A., Solov’yov A.V.

Focused electron beam induced deposition (FEBID) is a powerful technique for 3D-printing of complex nanodevices. However, for resolutions below 10 nm, it struggles to control size, morphology and composition of the structures, due to a lack of molecular-level understanding of the underlying irradiation-driven chemistry (IDC). Computational modeling is a tool to comprehend and further optimize FEBID-related technologies. Here we utilize a novel multiscale methodology which couples Monte Carlo simulations for radiation transport with irradiation-driven molecular dynamics for simulating IDC with atomistic resolution. Through an in depth analysis of $$\hbox {W(CO)}_6$$ deposition on $$\hbox {SiO}_2$$ and its subsequent irradiation with electrons, we provide a comprehensive description of the FEBID process and its intrinsic operation. Our analysis reveals that simulations deliver unprecedented results in modeling the FEBID process, demonstrating an excellent agreement with available experimental data of the simulated nanomaterial composition, microstructure and growth rate as a function of the primary beam parameters. The generality of the methodology provides a powerful tool to study versatile problems where IDC and multiscale phenomena play an essential role.

Turupcu A., Tirado-Rives J., Jorgensen W.L.

The binding energies for cation-π complexation are underestimated by traditional fixed-charge force fields owing to their lack of explicit treatment of ion-induced dipole interactions. To address this deficiency, an explicit treatment of cation-π interactions has been introduced into the OPLS-AA force field. Following prior work with atomic cations, it is found that cation-π interactions can be handled efficiently by augmenting the usual 12-6 Lennard-Jones potentials with 1/r4 terms. Results are provided for prototypical complexes as well as protein-ligand systems of relevance for drug design. Alkali cation, ammonium, guanidinium, and tetramethylammonium were chosen for the representative cations, while benzene and six heteroaromatic molecules were used as the π systems. The required nonbonded parameters were fit to reproduce structure and interaction energies for gas-phase complexes from density functional theory (DFT) calculations at the ωB97X-D/6-311++G(d,p) level. The impact of the solvent was then examined by computing potentials of mean force (pmfs) in both aqueous and tetrahydrofuran (THF) solutions using the free-energy perturbation (FEP) theory. Further testing was carried out for two cases of strong and one case of weak cation-π interactions between druglike molecules and their protein hosts, namely, the JH2 domain of JAK2 kinase and macrophage migration inhibitory factor. FEP results reveal greater binding by 1.5-4.4 kcal/mol from the addition of the explicit cation-π contributions. Thus, in the absence of such treatment of cation-π interactions, errors for computed binding or inhibition constants of 101-103 are expected.

Karimi-Maleh H., Cellat K., Arıkan K., Savk A., Karimi F., Şen F.

In this study, we report the synthesis and application of palladium-nickel nanoparticles decorated on functionalized-multiwall carbon nanotube Pd–Ni@f-MWCNT and employed as a sensitive non-enzymatic electrochemical glucose sensor. The composition and crystal structure was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy. The surface morphology of Pd–Ni@f-MWCNT was investigated by a transmission electron microscopy (TEM). The electrochemical response of the Pd–Ni@f-MWCNT to glucose was examined via the cyclic voltammetry. Results revealed that the prepared electrode exhibits high electrocatalytic activity for the oxidation of glucose into gluconolactone. The amperometric response of the Pd–Ni@f-MWCNT electrode to glucose was investigated at a potential of 0.5 V that demonstrated an extended linear range of from 0.01 to 1.4 mM, very low detection limit of 0.026 μM, very high sensitivity at 71 μA mM−1 cm−2, as well as good reproducibility, high stability and applicability for the real sample analysis. The reliability of the developed sensor was verified by comparison with a commercially available glucometer. The obtained results indicate that Pd–Ni@f-MWCNT is a promising candidate for electrochemical glucose sensing.

Luo Z., Lin X., Tang L., Feng Y., Gui Y., Zhu J., Yang W., Li D., Zhou L., Fu L.

Two-dimensional (2D) nanomaterials possessing a unique sheet structure, compared to correlative bulk materials, exhibit excellent properties, especially in the energy storage and energy conversion field. In this case, NiCl2 nanosheets with thicknesses of 2-8 nm are first prepared by a simple chemical vapor deposition method. For the Li-B/LiF-LiCl-LiBr/NiCl2 thermal battery, the specific energy of NiCl2 nanosheets increases from 510 W h kg-1 (NiCl2 rods) to 616 W h kg-1 at an operation temperature of 500 °C and a current density of 0.2 A cm-2. The 2D morphology and large numbers of defects not only improve the redox reaction rates and the lithium storage capacity, but also enhance the adsorption capacity with the flake-like binder MgO, which prolong the discharge time by suppressing the discharge product diffusion to the electrolyte. These results indicate that NiCl2 nanosheets have a great possibility to become a desirable candidate of cathode materials for assisting in the development of high energy output and provide a new way to restrain the immersion between the electrode and electrolyte.

Dai C., Li B., Li J., Zhao B., Wu R., Ma H., Duan X.

Mulitipe stoichiometric ratio of two-dimensional (2D) transition metal dichalcogenides (TMDCs) attracted considerable interest for their unique chemical and physical properties. Here we developed a chemical vapor deposition (CVD) method to controllably synthesize ultrathin NiS and NiS2 nanoplates. By tuning the growth temperature and the amounts of the sulfur powder, 2D non-layered NiS and NiS2 nanoplates can be selectively prepared with the thickness of 2.0 and 7.0 nm, respectively. X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization reveal that the 2D NiS and NiS2 nanoplates are high-quality single crystals in the hexagonal and cubic phase, respectively. Electrical transport studies show that electrical conductivities of the 2D NiS and NiS2 nanoplates are as high as 4.6 × 105 and 6.3 × 105 S·m−1, respectively. The electrical results demonstrate that the synthesized metallic NiS and NiS2 could serve as good electrodes in 2D electronics.

Liu H., Li Y., Fu Z., Li K., Bauchy M.

Interatomic forcefields for silicate glasses often rely on partial (rather than formal) charges to describe the Coulombic interactions between ions. Such forcefields can be classified as “soft” or “hard” based on the value of the partial charge attributed to Si atoms, wherein softer forcefields rely on smaller partial charges. Here, we use machine learning to efficiently explore the “landscape” of Buckingham forcefields for silica, that is, the evolution of the overall forcefield accuracy as a function of the forcefield parameters. Interestingly, we find that soft and hard forcefields correspond to two distinct, yet competitive local minima in this landscape. By analyzing the structure of the silica configurations predicted by soft and hard forcefields, we show that although soft and hard potentials offer competitive accuracy in describing the short-range order structure, soft potentials feature a higher ability to describe the medium-range order.

Deokar G., Casanova-Cháfer J., Rajput N.S., Aubry C., Llobet E., Jouiad M., Costa P.M.

Pristine, few-layer graphene (FLG)/Si nanopillar assemblies are introduced as gas sensitive chemiresistors showing unprecedented sensitivity towards NO2 when operated at room temperature (25 °C) and in humid air. To achieve this, we first developed wafer-scale (∼50 cm2) FLG growth using sub-micrometer thick films of thermally evaporated Cu/Ni on a SiO2/Si substrate. The Ni film was deposited and annealed to induce the formation of a Cu-rich binary alloy. This alloy formation limited the inter-diffusion of Cu and SiO2, a phenomenon known to take place during the CVD growth of graphene on Cu/SiO2/Si. The as-grown high structural quality FLG was transferred, using a conventional wet chemical method, to lithographically patterned arrays of Si nanopillars (non-flat substrate). Testing of the FLG/Si assembly revealed a NO2 sensitivity that outperforms what is reported in the literature for pristine graphene. Overall, our growth and device fabrication work-flow demonstrate a way to design graphene-based gas sensing systems without incurring inconvenient processing steps such as metal foil etching, surface functionalization or particle loading.

Su Q., Chen L., Yin L., Zhao J.

Safina L.R., Rozhnova E.A., Krylova K.A., Murzaev R.T., Baimova J.A.

Graphene reinforced metal matrix composites represent a promising class of materials for high-strength surface coatings because of their high strength and ductility. This study reports the application of different interatomic potentials to correctly describe the interaction between graphene and metals (Al, Cu, Ni, and Ti) by molecular dynamics. Both simple pair potentials, such as Lennard-Jones and Morse, and many-body potentials, such as bond order potential are applied for the simulation of a graphene/metal system at room temperature. Three different structures are considered: (i) graphene interacting with one metal atom; (ii) graphene interacting with a metal nanoparticle, and (iii) three-dimensional graphene network filled with metal nanoparticles. We first determine the potential energy that any graphene/metal system can reach during exposure at 300 K; then, we analyze the interaction dynamics for all considered systems and all potentials. A considerable difference in the interaction between metal nanoparticles with planar and folded graphene was found. For graphene/Ni, graphene/Cu, and graphene/Ti, the Lennard-Jones and Morse potentials yield accurate energetic and structural properties of the studied structures; they also describe interaction in the graphene/metal system in a similar way, at variance with bond-order potential. For graphene/Al, the Tersoff and Morse potentials describe the interaction better than Lennard-Jones. For the simulation of graphene/Me system, the optimal choice of the potential for different structures is of crucial importance. The presented analysis of the interatomic potentials appears to be promising for realistic and accurate simulations of graphene reinforced metal composites.