High entropy alloys (HEAs) in the hexagonal close-packed (hcp) phase usually show poor mechanical properties. We demonstrate here, by use of ab initio simulations and detailed experimental ...investigations, that the mechanical properties can be improved by optimizing the microstructure. In particular we design a dual-phase HEA consisting of a body-centered cubic (bcc) matrix and hcp laths, with nanoprecipitates of the ω phase in the Sc-Ti-Zr-Hf-Re system, by controlling the Re content. This dedicated microstructure reveals, already in the as-cast state, high compressive strength and good ductility of 1910 MPa and 8%, respectively. Our study lifts the hcp-based HEAs onto a competitive, technological level.
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•Ab initio calculations demonstrate the stabilization of the bcc and the ω phases when adding Re to the Sc-Ti-Zr-Hf system,•Detailed experimental observations including TEM analysis confirm the stabilization and reveal ω nanoparticles,•A mechanically superior dual-phase bcc+hcp microstructure strengthened by ω nanoparticles is designed
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•Super hardness and toughness of VSiN are achieved with Si content at 5.5 at.% Si.•With Si content, highly textured columnar grains, refined columnar grains, nanocomposite structure ...are formed.•DFT revealed that the ternary VSiN coatings become more ductile as the calculated Cauchy pressures (PC) raise, while the Pugh’s ratios (G/B) decrease.•Transfer of electrons to the Si-N bond from the neighboring V-N bonds causes Friedel oscillations and multiplication of the slip system.
Microstructural evolution and deformation mechanisms of magnetron sputtered V-Si-N coatings with various Si contents are investigated by transmission electron microscopy, X-ray absorption spectroscopy, and ab initio calculations. A small amount of Si atoms was dissolved into the cubic VN lattice, locally reducing the neighboring V-N p-d hybridization near the Si site. The Si content was found to impact the architecture of coating significantly. With increasing Si content, the microstructure evolved through three different architectures: (i) highly textured columnar grains, (ii) refined columnar grains, and (iii) nanocomposite structures where elongated grains were bounded by vein-like boundaries. Enhanced damage tolerance was observed in the nanocomposite structure, where multiple toughening mechanisms become active. Ab initio calculations revealed that the incorporation of Si monolayer in the (111)-oriented VN resulted in the formation of weaker Si-N bonds compared to V-N bonds, which allowed a selective response to strain and shear deformations by assisting the activation of the slip systems.
•We develop deep machine learning potential for Al-Cu-Ni melts in the whole composition range.•The potential provides excellent accuracy in comparison to ab initioand experimental data.•The potential ...reveals good compositional transferability.
The use of machine learning interatomic potentials (MLIPs) in simulations of materials is a state-of-the-art approach, which allows achieving nearly ab initio accuracy with orders of magnitude less computational cost. Multicomponent disordered systems have a highly complicated potential energy surface due to both topological and compositional disorder. That arises issues in MLIPs developing, such as optimal design strategy of potentials and their predictability and transferability. Here we address MLIPs for multicomponent metallic melts taking the ternary Al-Cu-Ni ones as a convenient example. We use many-body deep machine learning potentials as implemented in the DeePMD-kit to build MLIP that allows describing both atomic structure and dynamics of the system in the whole composition range. Doing that we consider different sets of neural networks hyperparameters and learning schemes to create an optimal MLIP, which allows archiving good accuracy in comparison with both ab initio and experimental data. We find that developed MLIP demonstrates good compositional transferability, which extends far beyond compositional fluctuations in the training configurations. The results obtained open up prospects for simulating structural and dynamical properties of multicomponent metallic alloys with MLIPs.
Lightweight alloys substitute steel in a wide range of industrial applications. It is still unclear whether the lubricant additives currently employed to reduce friction of sliding metallic parts are ...also efficient on non-ferrous substrates. In particular, the functionality of zinc dialkyldithiophosphates (ZDDPs) in contact with Al- and Mg-containing alloys still needs to be understood. In this work, we describe the properties of ZDDP at Al(111), Al(001), Al(331), Mg(0001) and Mg17Al12 surfaces and interfaces. Our calculations indicate that molecular fragments originated from ZDDP chemisorb more strongly on the intermetallic phase Mg17Al12 with respect to aluminum and magnesium, due to the higher surface energy of the mixed substrate. Ab initio molecular dynamics simulations show that the kinetics of the additive decomposition is significantly different on Al and the mixed phase. These results are supported by atomic force microscopy sliding tests, which revealed that the tribofilm formation is observed only on the latter substrate. This work suggests that the tribological performance of lightweight alloys can be enhanced by increasing the additive-surface chemical interactions.
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•Chemistry of lightweight alloys governs the efficiency to form ZDDP-based tribofilms.•AIMD and AFM show that ZDDP cannot efficiently decompose on aluminum surfaces.•The decomposition of ZDDP on the mixed Mg17Al12 phase is instead favorable.•Affinity between S and Mg atoms drives the initial step of the tribochemical reaction
Curcuma derivatives are widely used as natural pigments in the food industry. Recent biological studies demonstrated that one of its major components, curcuminoids, might also positively impact human ...health. Herein, we use theoretical tools to combine cisplatin, the golden standard of chemotherapy, to curcuminoid analogues that have previously shown anticancer properties. Our goal is to rationalize the design of a series of prodrugs prone to be photo-activated by visible light. The simulations performed in this contribution disclose two novel complexes absorbing in the first phototherapeutic window, i.e., in the 600–800 nm domain. The optimizations of these structures within the framework of photoactivated chemotherapy are discussed.
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•Curcuma derivatives are natural pigments with positive biological properties.•However, medical application fails due to their low bioavailability.•Combination of the parent curcuma with cisplatin prevents early degradation.•Theory is used here for searching enhanced cisplatin-curcuminoids prodrugs.•We report two novel complexes that are compatible with photoactivation.
A phosphate glass (PG) composite based on the ternary system 75 mol% P2O5–15 mol% Nb2O5–10 mol% Bi2O3 was fabricated via the one-step melt-quench method and its anti-corrosion performance was ...evaluated using systematic experimental and theoretical approaches. XRD, Raman spectroscopy, AFM and SEM-EDX techniques were used to confirm the successful synthesis of PG. XRD and DSC disclosed the amorphous nature of the fabricated glass. Weight loss method, Tafel polarization and EIS revealed high inhibition performance of the doped PG toward low carbon steel in the aggressive 1 M HCl medium at different temperatures. Tafel polarizations demonstrated the superior corrosion protection of PG via a mixed-type mechanism with anodic predominance. The protection efficiency, obtained from EIS, increased with increasing the PG concentration, reaching up to 87 % for 250 ppm PG, which agrees with the Tafel analysis result. Further, SEM and AFM images verified that the steel surface is effectively protected by a robust layer of PG. Adsorption isotherms revealed that both physisorption and chemisorption are involved at the steel-electrolyte interface. Ab initio simulations were performed, for the first time on phosphate glass, and unraveled a shielding effect and high electron donating ability of PG, reflecting its strong adsorption, hence explaining its protection effectiveness at the molecular level.
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•Bi- and Nb-oxide-doped phosphate glass (PG) composite was successfully developed and characterized.•PG exhibited remarkable mixed-type corrosion protection to steel at different temperatures.•Adsorption isotherms revealed involvement of both physisorption and chemisorption.•AFM and SEM images demonstrated the efficient protection by a robust barrier layer.•Ab initio simulations gave insights into the adsorption and inhibition mechanism at the molecular/atomic level.
The ML boron phosphide (BP) SBFETs with ML Zr2NF2 and 2H-VS2 electrode show n- and p-type Ohmic contact, respectively, and the device performances in terms of Ion, τ, and PDP surpass the IRDS HP ...targets for the year 2037 and are superior to the Ion of several former studied ML SBFETs with ML metal electrodes.
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•The electrical contact properties of semiconducting ML boron phosphide (BP) with ML metallic MXenes and metallic TMDs are studied using ab initio calculations.•N- and p-type (quasi-) ohmic is obtained with low- and high-work-function ML metals.•The n-/p-type 9-nm-Lg ML BP SBFET with ML Zr2NF2/2H-VS2 electrode at Vdd = 0.5 V surpasses the IRDS HP target for the year 2037 in terms of Ion, τ, and PDP, and Ion superiors to several ML SBFETs with ML metal electrodes.•The physical mechanism of electrode impact on leakage and on-state currents is uncovered.
Pursuing low contact resistance is crucial for ameliorating performances of short-channel Schottky barrier field effect transistors (SBFETs). We have studied the electrical contact properties of semiconducting monolayer (ML) boron phosphide (BP) with metallic MXenes (Zr2NF2, Zr2CF2, Ti2NF2, and Ti2CF2) and metallic TMDs (1T-TaS2, 2H-TaS2, 1T-VS2, and 2H-VS2) using ab initio calculations. The BP/MXene and BP/TMD contacts have clean interfaces without metal-induced gap states and show weak Fermi-level pinning. The n- and p-type (quasi) ohmic contact is obtained with low-work-function metals (Zr2NF2 and Zr2CF2) and high-work-function metals (2H-TaS2, 2H-VS2, and 1T-VS2), respectively. The 9-nm-gate ML BP SBFET with Zr2NF2 (2H-VS2) electrode is an n- (p-) type high-performance (HP) device with the on-state current (Ion), delay time (τ), and power dissipation (PDP) of 1872 (1129) μA/μm, 0.29 (0.15) ps, and 0.27 (0.09) fJ/μm at a supply voltage of Vdd = 0.5 V, surpassing the 12-nm-gate International Roadmap for Device and Systems (IRDS) HP targets for the year 2037 at Vdd = 0.6 V and superior to the Ion of several previously studied ML SBFETs with ML metal electrodes at Vdd = 0.5–0.74 V with 9–10 nm gate. Our study suggests that ML BP SBFETs (with ideal electrodes) are promising candidates for HP applications for more Moore electronics.
The static and dynamic properties of several bulk liquid 4d transition metals at thermodynamic conditions near their respective melting points have been evaluated by using ab-initio molecular ...dynamics simulations. The calculated static structure factors show an asymmetric second peak followed by a more or less marked shoulder which points to a sizeable amount of icosahedral local order. Special attention is devoted to the analysis of the obtained longitudinal and transverse current spectral functions and the corresponding dispersion of collective excitations. For some metals, we have found the existence of two branches of transverse collective excitations in the second pseudo-Brillouin zone. Finally, results are also reported for several transport coefficients.
•First ab initio simulations of some liquid 4d metals.•Good agreement with available experimental structure.•Prediction of important properties, such as diffusivity, sound velocity and viscosity.
We conducted ab initio molecular dynamics simulations to study the structural and dynamical properties in Al80Ti20 liquids. The prepeak that represents some chemically ordered structure, emerges in ...the partial static structure factors at low temperatures. By calculating coordination numbers, we found a preferred connection for Al–Ti pairs, which induces an excess Ti/Al concentration around the central Al/Ti atoms. An excess Ti concentration is even found in the second neighbour shells around Ti atoms, rationalizing the prepeak as the result of chemical concentration fluctuation in these neighbour shells. Concomitantly, slow structural relaxation occurs below 1400K, exhibited as the second step relaxation in self-intermediate scattering function. The slow dynamics induces a non-Arrhenius transition for the temperature-dependent diffusivity and structural relaxation time, as well as the breakdown of the Stokes–Einstein relation. These results unveil the detailed ordering structure for the chemical interaction and the associated dynamical behaviour in Al80Ti20 liquids.
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•Prepeak emerges in partial static structure factors upon cooling down in Al80Ti20 melts.•Excess chemical concentration finds even in the second neighbour shells of atoms.•Slow dynamics happens at the crossover temperature where the prepeak becomes significant.•Stokes–Einstein relation nearly holds on with the diffusivity of Ti.
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