Highlights • Classical Taylor model proves inadequate for strain prediction. • Micromechanical Taylor Factor outperforms in capturing local effects. • Work-hardening models improve with Micromechanical Taylor Factor. • Different insights into dislocation mechanisms using refined approach. • Potential to revolutionize materials design with greater precision. This study uses Fast Fourier Transform (FFT) simulations in the Düsseldorf Advanced Material Simulation Kit (DAMASK) to investigate the influence of the micromechanical Taylor Factor on the work hardening parameters. Departing from the assumption of a homogeneous deformation in the classical Taylor model, we use the micromechanical Taylor Factor, which takes better account of local grain interactions and strain distributions. Our comparison of simulations using both classical and micromechanical Taylor factors reveal crucial differences in the predicted dislocation mechanisms, leading to different interpretations of work hardening behavior. Our results question the adequacy of conventional models and suggest a more sophisticated understanding of the deformation of polycrystalline materials. The study underscores the importance of an improved modeling approach to characterize deformation and leads to a re-assessment of existing predictive mechanisms in materials science with possible implications for optimizing of material performance. Graphical abstract Download : Download high-res image (259KB) Download : Download full-size image

By employing atomic material properties (i.e., elastic moduli and general stacking fault energy (GSFE)) of Ni3Al with L12 structure, we predict a series of core configurations of dislocations with edge and screw characters associated with slip systems of ( 1 1 1 ) 0 1 1 ¯ and ( 0 0 1 ) 1 1 0 under various external applied stresses. For the slip system of ( 1 1 1 ) 0 1 1 ¯ , the dislocation cores are found to consist of one APB and two CSF faults, with a larger core for the edge dislocation than for the screw. Such multi faults core configuration is missing for the ( 0 0 1 ) 1 1 0 slip system, where only a larger APB fault is present due to a lower APB energy on ( 0 0 1 ) as compared with that on ( 1 1 1 ) . The dissociation mechanism for full dislocations into super partials and possible faults under different applied shear stresses are carefully investigated. It is found that the core structures (including APB, CSF and SISF faults) exhibit different degrees of dependence on the direction and magnitude of the applied stresses. The evolution of local displacements exhibits a specific sequence of “full dislocation → SISF → APB”, which can be modulated by the variation of stresses. Graphical abstract Download : Download high-res image (163KB) Download : Download full-size image

Highlights • This study analyses the stability of COFs at 37 °C and 42 °C and their impact on the binding and interaction energies with DOX. • vdW interactions contribute most to DOX-COF binding energy, while ES and HB interactions were negligible. • The COFs with small polar or non-polar substitutions were unsuitable for DOX release. • COF-HQ with bulky substitution having the highest binding energy, and placement of DOX between the COF substitution layers impeded the temperature effect to release DOX. • DOX release was observed only in COF-OMe at the higher temperature of 42 °C. Nowadays, drug release through temperature control between healthy and cancer cells is also one of the most critical topics in drug delivery. Covalent organic frameworks (COFs) with specific structural units and functional groups can be optimized for efficient smart drug delivery applications. Hence, in the present study, a detailed systematic study on the release of the anticancer drug doxorubicin (DOX) in a temperature-sensitive method from COFs with structural units of 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde substituted with hydrogen (COF-H), ethyl (COF-Et), hydroxyl (COF-OH), methoxy (COF-OMe) and 8-hydroxyquinoline (COF-HQ), by molecular dynamics (MD) simulation method at two temperatures of 37 °C and 42 °C was performed. In addition to the stability of COF systems at 37 °C and 42 °C, the results showed that changing the temperature and substitution effectively changes the binding and interaction energies between the DOX and COFs. It was understood that van der Waals (vdW) interactions, in contrast to electrostatic (ES) interactions, have the major contribution to the binding energy ( Δ G bind ° ). Also, hydrogen bonding (HB) can be effective in binding between the DOX and COFs capable of donating and accepting HBs, such as COF-HQ and COF-OH. It was seen that COFs with completely polar substitution (COF-OH) or completely non-polar substitution (COF-Et and COF-H) were unsuitable, because the DOX establishes strong interactions with these COFs by being placed on the inner surface of the cavities of the COF backbone. Also, COF with bulky substitution, COF-HQ, has the highest Δ G bind ° = −45.9108, but it was observed, due to the gradual placement of the DOX between the COF substitution layers, increasing the temperature was not able to release the DOX. Finally, DOX release was observed among the five COF systems in COF-OMe at 42 °C ( Δ G bind ° = −21.0080 kcal/mol). But at 37 °C, due to the absorption of the DOX inside COF-OMe cavities ( Δ G bind ° = −30.9486 kcal/mol), DOX release was not observed. Graphical abstract Download : Download high-res image (188KB) Download : Download full-size image

Black phosphorene (BlackP), like α-SiS, is a two-dimensional semiconducting material for advanced microelectronics, with a moderate band gap. Even yet, the epitaxial growth of α-SiS on a fertile substrate has proven to be a formidable obstacle, delaying its widespread production for technological applications. Here based on first-principles approaches we identify that α-SiS (which is not a layered material in bulk form) monolayer could be stabilized either in freestanding form or supported on few layers of a BlackP substrate owing to its isovalency nature and the inherent structural resemblance between the two. Our calculation results demonstrate that α-SiS monolayer is stable on BlackP. Furthermore, the synergistic interfacial effect makes BlackP-like α-SiS and BlackP (α-SiS/BlackP) van der Waals (vdW) heterostructure a viable contender for power-driving sodium-ion batteries owing to relatively high binding strength, ultrafast diffusivity (0.08 eV in region-III), transition from semiconducting to upon sodiation, and substantially high theoretical capacity (329 mAhg−1). Moreover, the α-SiS/BlackP vdW heterostructure possesses high optical absorption strength ∼105 cm−1, and can effectively harvest visible solar radiation. The α-SiS growth on such semiconducting substrates could become a novel platform for next-generation nano-energy technology. Graphical abstract The α-SiS growth on such semiconducting substrates could become a novel platform for next-generation nanoenergy technology. Download : Download high-res image (184KB) Download : Download full-size image

Density Functional Theory (DFT) calculations were performed to assess the mechanical properties of an Ir metal nanocluster. The properties under investigation encompassed the bulk modulus, Poisson ratio, elastic shear modulus, and binding energy. The stability of the nanocluster was explored across various shapes, including icosahedron, octahedron, and truncated octahedron, with consideration given to different cluster sizes. The DFT results unveiled a general mechanism for amorphization in the Ir nanocluster of size 55, involving rosette-like structural transformations at the fivefold vertex. Additionally, Phonon Density of States (PDOS) was computed for the core, surface, and total atoms of Ir nanoclusters with sizes 38, 55, and 75, as well as for the Ir bulk structure. These calculations were carried out using both Quantum Sutton-Chen potential (QSC) and Gupta potential models through molecular dynamics (MD) methods. The analysis of the phonon density of states revealed that the contributions of two main peaks in low and high frequencies were associated with the surface and core atoms, respectively. Furthermore, the extension of the phonon density of states was performed for larger-sized Ir nanoclusters. Significantly, the QSC potential was utilized to investigate the adsorption of main peaks and their trends for the phonon density of states in the Ir bulk structure. The results obtained from this method were found to be in agreement with experimental data derived from cold neutron and multidetector time-of-flight spectrometer phonon measurements. Graphical abstract Download : Download high-res image (122KB) Download : Download full-size image

Highlights • The melem/graphene and melem/graphite interfaces were characterized. • Changes in the electronic structure and surface-related parameters of the new organic/organic interface were analysed. • Carbon dioxide adsorption on melem/graphene versus graphene was studied. Through first-principles simulations, we studied the properties of organic/organic interfaces as melem was adsorbed on graphene or graphite. The interaction between molecule and substrate was quantified through the adsorption energy. This parameter results from changes in the geometry of the system, partial charge transfer process and generation of a net interfacial dipole. Different adsorption positions on pristine and defective surfaces were analysed. Defective graphene sheets are more flexible than pristine ones, favouring adsorption. However, surface defects on graphite terrace are not preferential adsorption sites. These modified materials have different electronic structures and amino groups. Thus, they can be used as catalysts since they improve the carbon dioxide uptake by hydrogen bond interactions. Graphical abstract Download : Download high-res image (351KB) Download : Download full-size image

Highlights • The material properties discount calculation method based on fiber distribution was proposed; • The node heat transfer judgment and coupling technique based on the fiber diameter was proposed; • The number of meshes required for composite modeling can be significantly reduced based on the MPDCM and NGTJCT; • The modulus, strengths, and thermal conductivities of 3D SCf/UHTCMCs were evaluated. Conducting precise and consistent research into the mechanical and thermal properties of 3D short fiber-reinforced ultra-high temperature ceramic matrix composites (SCf/UHTCMCs) is essential for the lightweight design optimization of structures operating under extreme loads. While the current use of one-dimensional elements to simplify fiber solids addresses the mesh quantity and quality issues stemming from the demand for periodic cell size, it fails to accurately predict the mechanical and thermal properties of SCf/UHTCMCs. This research developed material models featuring fiber volume fractions ranging from 0 to 15%, derived from statistical data on the aspect ratio distribution of short fibers. Addressing the unique characteristics of SCf/UHTCMCs, we proposed the Material Properties Discount Calculation Method (MPDCM), which leverages fiber distribution to calculate the mechanical properties and thermal conductivity of composite materials. Furthermore, we introduced the Node Heat Transfer Judgment and Coupling Technique (NGTJCT), rooted in fiber diameter, to address the issue of unrealistic heat transfer between fiber nodes and matrix nodes in numerical assessments. Utilizing both MPDCM and NGTJCT allows for a substantial reduction in the required mesh count for composite modeling, while adhering to the dimensional needs of periodic cells and facilitating rapid and precise numerical analysis of 3D short fiber-reinforced composites. The outcomes of this research have the potential to overcome the existing bottleneck in the numerical analysis of SCf/UHTCMCs, minimize the necessity for complex experimental procedures in material performance studies, and lay the groundwork for engineering optimization design. Graphical abstract Download : Download high-res image (360KB) Download : Download full-size image

Due to the highest conversion efficiency of β-CsPbI3 among all the inorganic halide perovskite solar cells, it has attracted widespread attention. This paper systematically studies the formation energy and transition energy level of intrinsic point defects for β-CsPbI3 by using first-principles. The results demonstrate that growth of β-CsPbI3 is greatly affected by the Cs concentration and its growth window is extremely small. Although β-CsPbI3 has some deep-level defects, the formation energies of these defects are relatively high with positive values. Both under Pb-rich and Pb-poor conditions, the transitional energy levels of main intrinsic acceptor defect Pb vacancy (denoted as VPb) is in the valence band, which induces a high hole carrier concentration. Therefore β-CsPbI3 is considered as an excellent p-type semiconductor. It might be used to as a potential candidate of inorganic perovskite materials for solar cell absorber. Graphical abstract Download : Download high-res image (216KB) Download : Download full-size image

Molecular ferroelectrics exhibit various advantages as compared to the traditional oxide ferroelectric materials. Despite tremendous experimental and theoretical efforts in the optimization and understanding of molecular ferroelectric systems, their domain-switching dynamics are yet to be discovered. In this study, we use the Imidazolium perchlorate thin films, a representative molecular ferroelectric material as the model system to systematically investigate the domain switching dynamics under a local bias through a Piezoelectric Force Microscopy (PFM) tip. We employed both thermodynamic calculations and the phase-field approach to explore the effects of various factors, including the magnitude of electric bias, distance to the domain wall, domain size, and substrate strain, on the domain switching behavior. Under intermediate bias, local ferroelastic 109° switching dominates. It is shown that the local 180° switching can occur with multiple sluggish and consecutive 71° switching when the tip is placed far away from the original 180° domain wall; whereas when the tip is placed near the domain wall, the bending of the domain wall towards the tip center can be seen, forming stable curved 180° domain walls. Moreover, the larger the domain size, the smaller the switching area; while the clamping effect from the substrate can inhibit domain switching, leading to a lower switching area with a higher magnitude of compressive strain. We hope to spur further interest in the understanding, designing, and optimization of the molecular ferroelectric thin films. Graphical abstract Download : Download high-res image (197KB) Download : Download full-size image

Highlights • Uniaxial strain is key to tuning of material properties, including magnetic phases. • Decoupling effect of type of strain from geometrical effects by forming square lattice. • Compressive strain leads to FM insulator by reduction of Jahn–Teller distortion. • Correlation plays strong role; DFT gives metal, DMFT gives insulator. • Tensile strain give AFM insulator; Flavor of strain is more important than geometry. Recent years have seen tremendous progress in experimental techniques to create uniaxial strain. Motivated by these advances we investigate the effect of uniaxial strain on LaMnO 3 employing ab-initio dynamical mean-field theory, and put it in contrast to biaxial strain that occurs in epitaxial systems. Projecting on the low-energy subspace of Mn 3 d states, and solving multi-impurity problems, our approach emphasizes on local dynamic correlations at Mn sites. At ambient pressures, LaMnO 3 crystallizes in an orthorhombic unit cell, with in-plane lattice constants a < b , and shows an A-type antiferromagnetic ground state. If we apply uniaxial compressive strain such that the in-plane lattice becomes square with lattice constant a , we find a ferromagnetic insulating state. This is in sharp contrast to DFT results using various functionals like PBE, PBE+ U , and hybrid functionals like HSE, which all predict a half-metallic ferromagnetic behavior. Interestingly, applying uniaxial tensile strain, such that the in-plane lattice becomes square with the longer lattice constant b , an antiferromagnetic insulating state is observed. We trace back these results to the reduction in Jahn–Teller distortion in the case of compressive strain, favoring a ferromagnetic state. This reduction is absent in the tensile case, and the antiferromagnetic state therefore survives. Our study shows that it is the flavor of the strain (compressive or tensile) which is decisive for the magnitude of Jahn–Teller distortions and, hence, the magnetic state. Graphical abstract Download : Download high-res image (226KB) Download : Download full-size image