Deformation Potential Research Articles

Impact penetration response of fiber metal laminates padded with 3D continuous fiber-reinforced polyurethane foam

Novel composite combinations are needed to meet the broad mechanical requirements for lightweight structures by integrating various properties within a single structure. This includes high structural rigidity and impact resistance with low overall density. Fiber metal laminates (FMLs) are advanced composite materials composed of an alternating stacking sequence of metal alloys layers and fiber-reinforced polymers. However, FMLs exhibit lower puncture deformation potential compared to fiber-reinforced thermoplastics (FRTPs). To address this limitation, polyurethane (PUR) foam with 3D continuous fiber-reinforcement, is investigated as padding. The FML, manufactured via thermoforming, is based on basalt fiber-reinforced polyamide 6 and two layers of aluminum alloy. The PUR foam is fabricated through structural reaction injection molding and reinforced with a spacer fabric. Subsequently, low velocity impact tests are conducted for this novel composite and its single components. The results unveil significant insights into the impact behavior of the materials. The highest perforation resistance of 81 J is achieved by the FML padded with 3D continues fiber-reinforced polyurethane foam while offering equal deformation capability as without reinforced PUR foam. These findings underscore the superior impact performance of the fiber metal laminate padded with 3D continues fiber-reinforced polyurethane foam, offering valuable insights for the advancement of impact-resistant materials in various engineering applications.

The BeP2 monolayer exhibits ultra-high and highly anisotropic carrier mobility and 29.3% photovoltaic efficiency.

Two-dimensional materials with a combination of a moderate bandgap, highly anisotropic carrier mobility, and a planar structure are highly desirable for nanoelectronic devices. This study predicts a planar BeP2 monolayer with hexagonal symmetry that meets the aforementioned desirable criteria using the CALYPSO method and first-principles calculations. Calculations of electronic properties demonstrate that the hexagonal BeP2 monolayer is an intrinsic semiconductor with a direct band gap of approximately 0.94 eV and this direct bandgap characteristic is maintained under strain. The mobilities of hexagonal BeP2 are electron-dominated, reaching ∼105 cm2 V-1 s-1, which is two orders of magnitude higher than the mobility of holes. The high carrier mobility results from the small deformation potential constant, which arises from the unique decoupling behavior of electrons in the valence and conduction bands. Furthermore, our calculations reveal that the photovoltaic efficiency of hex-BeP2 is as high as 29.3%, which is comparable to those of well-known thin-film solar cell absorbers, thanks to its high visible light absorption coefficient of ∼105 cm-1 and its direct bandgap feature.

Structural and electronic features enabling delocalized charge-carriers in CuSbSe2

Inorganic semiconductors based on heavy pnictogen cations (Sb3+ and Bi3+) have gained significant attention as potential nontoxic and stable alternatives to lead-halide perovskites for solar cell applications. A limitation of these novel materials, which is being increasingly commonly found, is carrier localization, which substantially reduces mobilities and diffusion lengths. Herein, CuSbSe2 is investigated and discovered to have delocalized free carriers, as shown through optical pump terahertz probe spectroscopy and temperature-dependent mobility measurements. Using a combination of theory and experiment, the critical enabling factors are found to be: 1) having a layered structure, which allows distortions to the unit cell during the propagation of an acoustic wave to be relaxed in the interlayer gaps, with minimal changes in bond length, thus limiting deformation potentials; 2) favourable quasi-bonding interactions across the interlayer gap giving rise to higher electronic dimensionality; 3) Born effective charges not being anomalously high, which, combined with the small bandgap (≤1.2 eV), result in a low ionic contribution to the dielectric constant compared to the electronic contribution, thus reducing the strength of Fröhlich coupling. These insights can drive forward the rational discovery of perovskite-inspired materials that can avoid carrier localization.

Optical properties of 2D GeTe under strain: A DFT study

Monolayer germanium telluride (GeTe) exhibits tunable electronic and optical properties, making it promising for device applications. Using Density Functional Theory (DFT), we investigate the impact of uniaxial strain, ϵ, on its band structure and dielectric function (DF), ε̃. Tensile strain along the —zigzag direction induces a direct-to-indirect bandgap transition at ϵ = 2%, reducing the gap from 1.80 to 1.62 eV. Compressive strain narrows the gap while maintaining its indirect nature. Strain also induces in-plane anisotropy in the DF and shifts the optical absorption spectrum. We determine a deformation potential (DP) of −6.45 eV for the bandgap under tensile strain and DPs for other above bandgap high-symmetry points. These findings highlight the potential of strain engineering for tuning GeTe’s properties in devices.

A FINITE ELEMENT MODEL FOR CALCULATING A NON-THIN ORTHOTROPIC CYLINDRICAL SHELL, TAKING INTO ACCOUNT THE INDUCED INHOMOGENEITY

The formulation of a model for the deformation and strength calculation of an open cylindrical shell of circular shape rigidly pinched along contour planes formed by generators is considered. The ratios of the geometric parameters of the shell differ significantly from thin-walled structures, to which traditional technical hypotheses could be applied. The formulation of a mathematical model defining the stress-strain states of a thick-walled structure was carried out within the framework of a nonlinear three-dimensional theory. The peculiarity of the developed model was that orthotropic composites were adopted as the structural materials of the shell, the deformation and strength properties of which manifest themselves in different ways in accordance with the types of stress states being realized. The manifestation of such mechanical properties of materials is interpreted as induced heterogeneity, which significantly complicates the methodology for calculating spatial structures. Due to the specified features of the research object, isoparametric finite elements of a three-dimensional tetrahedral shape, the nodes of which had three degrees of freedom, were used to develop a computational model. In order to adequately account for the stiffness properties of orthotropic composites exhibiting induced heterogeneity, the basis of the determining relationships for them was the deformation potential formulated in the normalized stress tensor space associated with the main axes of orthotropy of materials. Due to the nonlinearity of the problem under consideration, the process of solving it was based on the method of variable elasticity parameters. As a result of the implementation of the computational model, comprehensive information was obtained on the stresses, deformations and displacements of the shell, the main of which are presented in the text of the article with the addition of their analysis.

Acoustic Phonon Scattering in Free‐Standing Anisotropic Silicon Plates

The electron–acoustic‐phonon interaction in a free‐standing anisotropic Si plate with (001) surface is studied taking into account the elastic anisotropy of the Si crystal and the modulated phonon modes. The interaction potential is derived from the modulated phonon modes and the anisotropic deformation potential constants. The effective deformation potential constant Dac is then calculated considering only the lowest electronic sub‐band. In the quantum well model for the electronic states, it is shown that the effective deformation potential for the modulated phonons in an anisotropic Si plate becomes Dac ≈ 13 eV in the thinner region of the plate thickness . It is also shown that both the phonon modulation and the crystal anisotropy have non‐negligible effects on the effective deformation potential and electron mobility.

Inter-valley phonon scattering limited performance of n-channel WS2 monolayer transistors

Abstract In addition to the K conduction band valley of monolayer WS2, there is a remote Q valley located 0.1 eV above the K valley. We investigate the effects of intra- and inter-valley phonon scattering, including K ↔ Q inter-valley scattering, on monolayer WS2 device performance using a recursive Green’s function algorithm and the Büttiker probe scattering model. Our analysis reveals that ballisticity drops to 54% when only intra-valley phonon scattering is considered. When inter-valley phonon scattering (excluding K ↔ Q inter-valley scattering) is added, ballisticity decreases to 42%. This further declines to 12% with the inclusion of K ↔ Q inter-valley scatterings. Similarly, low-field mobility values decrease successively from 395 cm 2 ( V ⋅ s ) − 1 to 223 cm 2 ( V ⋅ s ) − 1 and then to 110 cm 2 ( V ⋅ s ) − 1 at a sheet density of 109 cm−2. The primary scattering mechanism responsible for this degradation is K → Q inter-valley acoustic phonon scattering, characterized by a high deformation potential of 7.3 × 10 8 eV cm − 1 and a low energy of 16.76 meV. Additionally, K → Q inter-valley scattering significantly populates the Q valley, which presents a higher potential barrier in the on-state conduction band profile, resulting in a lower on-state current. Our analysis shows that approximately 40% of the on-state total power dissipated within the device is due to phonon scattering effects, with the remainder being released through thermalization in the device’s contacts.

Giant deformation potential induced small polaron effect in Dion–Jacobson two-dimensional lead halide perovskites

Abstract Halide perovskites have attracted much attention recently. However, the strong lattice distortion effects in these materials have led to debates regarding the nature of charge carriers. While the behavior of carriers in bulk three-dimensional materials is well-documented, the characteristics of carriers in two-dimensional perovskites remain less understood. In this study, we provide direct and clear evidence of small polaron formation through transient spectroscopic analysis of deformation potential and dynamic lattice screening. Coherent acoustic phonon wave signals reveal a strong coupling between carriers and lattice degrees of freedom, leading to small polaron formation and a spin lifetime enhancement of up to tenfold. Utilizing optical Kerr spectroscopy and theoretical modeling, we observed a notably long polarization response time at room temperature, attributed to lattice distortion and small polarons approximately two-unit cells in size. Temperature-dependent coherent phonon dynamics and X-ray diffraction further confirmed the presence of small polarons. This discovery underscores the significance of the cooperative interplay between exciton dynamics and the small polaron field, particularly in influencing the Coulomb exchange interaction of excitons.

Optimizing Reduction Guide Stability in Osteotomy Using Patient-Specific Instrumentation: A Basic Guideline.

The use of patient-specific instruments (PSIs) for osteotomies is becoming more popular in orthopaedic surgery for correcting mechanical axis and posttraumatic deformities. However, the PSI reduction guides have great potential for intraoperative deformation, which adversely affects the accuracy of the procedure. To conduct a finite element analysis (FEA) to analyze different design parameters to improve the intraoperative stability of the reduction guides. Descriptive laboratory study. A reduction guide with a rectangular cross section and four 4-mm K-wire slots was simplified, and the following parameters were modified: width, height, profile design, K-wire thickness, and positions. Bending and torsional moments were applied to the guide construct and guide deformation and equivalent stress were determined using FEA. Increasing the profile height by 25% resulted in a 44% reduction in guide deformation for bending (37% for torsion). A 25% increase in profile width led to an 18% deformation reduction for bending (22% for torsion). Transverse K-wire slots resulted in 51% less deformation in torsion compared with longitudinally oriented slots. Placing the central K-wire slots 25% closer to the osteotomy reduced guide deformation by 20% for bending and 11% for torsion. The most effective methods to increase reduction guide stability are to increase the guide height and reduce the central K-wire distance to the osteotomy. When performing opening or closing wedge osteotomies, which mainly involve bending of the guide, a high-profile guide and longitudinally oriented K-wire slots should be used. When torque is expected as in rotational osteotomies, the K-wire holes in guides should be oriented transversely to reduce intraoperative deformation.

Tl2XY (X, Y = S, Se) monolayers with low lattice thermal conductivity and high thermoelectric performance by full-band approach with four scattering mechanisms

Abstract The low lattice thermal conductivity and high thermoelectric performance of the Janus Tl2SSe monolayer in the temperature region of 300–700 K are identified based on the thermoelectric properties of the Tl2S2, Tl2SSe, and Tl2Se2 monolayers. The transport coefficients for carrier concentrations and temperatures are obtained by solving the linearized Boltzmann transport equation in a full-band electronic structure. Four scattering mechanisms of acoustic deformation potential, optical deformation potential, polar optical phonon, and ionized impurity scatterings are considered. The ionized impurity scattering is recognized as the most important. The lattice thermal conductivity of the Janus Tl2SSe monolayer is substantially smaller than those of the Tl2S2, Tl2Se2 monolayers with higher symmetry. Moreover, we find that the Janus structures of the Tl2SSe monolayer increase the dielectronic constants and enhance the polar optical phonon scattering, then reduce the power factor to some extent. Therefore, the lattice thermal conductivity actually couples with the transport coefficient and cannot be individually regulated as is usually assumed. However, the ZT value of the Tl2SSe monolayer can still reach 1.77 at 700 K even if the intrinsic concentration and the bipolar effect are included. Therefore, the Tl2SSe monolayer is expected to be a promising candidate for thermoelectric materials.

Ensemble Monte Carlo transport studies of zinc-blende cuprous halides

We present a comprehensive theoretical analysis of intrinsic high-field transport in cuprous halides: CuCl, CuBr, and CuI. Ensemble Monte Carlo transport simulations were performed based on analytical approximations of the multi-valley and three-band electronic structure model. The deformation potentials, extracted from carrier–phonon interaction matrix elements calculated via the Wannier function approach, were employed to determine scattering rates. Our detailed analysis uncovers intriguing transport characteristics based on the complex valence band structures, resulting from spin–orbit coupling and band inversion. Remarkably, the hole mobility in CuI was exceptionally high, reaching up to 193 cm2/V s, while CuCl exhibited unusual temperature dependencies in hole transport. Additionally, the electron mobility in CuI was found to be 254 cm2/V s, indicating a minimal disparity between carrier mobilities, which is advantageous for optoelectronic applications.

"Revolutionizing auricular seroma treatment: exploring diverse surgical strategies with a comprehensive case study".

Auricular seromas present a significant therapeutic challenge due to their propensity for recurrence and potential for cosmetic deformity. This case series illustrates the effective management of post-traumatic auricular seromas through diverse surgical approaches in two patients. Each case highlights the use of different splinting materials post-surgery, detailing the clinical presentations, surgical interventions, and follow-up outcomes. Additionally, the study reviews alternative treatment modalities reported in the literature, providing a comprehensive overview of current strategies for managing auricular seromas. By exploring these cases, the study enhances understanding of the surgical strategies and their outcomes, emphasizing the importance of tailored treatments for auricular seromas.

Nonlinear Finite Element Analysis of Bone–Implant Contact in Three Short Dental Implant Models with Varying Osseointegration Percentages

Objectives: Dental implants have become a cornerstone of restorative dentistry, providing a long-lasting method for tooth replacement. The degree of osseointegration has a significant effect on biomechanical stability at the bone–implant contact (BIC), determining the continued efficacy of these implants. However, the exact consequences of changing osseointegration levels on different implant designs, especially in bones with variable densities, are not well known. Methods: This study used 3D finite element analysis (FEA) to look at the biomechanical performance of three short dental implants: BioMet 3iT3, Straumann® Standard Plus Short-Regular Neck (SPS-RN), and Straumann® Standard Plus Short-Wide Neck (SPS-WN). This paper tested the implants at four stages of osseointegration: 25%, 50%, 75%, and 100% in both high-density (bone type III) and low-density (bone type IV) cancellous bone. It also created and examined realistic CAD models under static occlusal loading conditions to assess stress distribution and major strains at the bone–implant contact. Results: The study discovered that as osseointegration increases, von Mises stress and principal strains go down significantly for all implant types. The SPS-WN implant had the lowest strain values, especially for bone with low density. These reductions demonstrate increased mechanical stability as the bone–implant interface becomes more capable of dispersing mechanical stresses, minimizing the potential for localized deformation and bone resorption. Conclusions: The results highlight the importance of achieving optimum osseointegration to reduce mechanical stress and increase the lifespan of dental implants. The SPS-WN type implant performed better in biomechanical tests than the others, especially when bone conditions were not ideal. This makes it a great choice for clinical applications that need long-term implant success.

A novel cellular structure with center-symmetric cell walls for morphing applications

Cellular structures are potential candidates for the supporting framework of flexible morphing skins. Unlike traditional zero Poisson’s ratio (ZPR) cellular structures with axisymmetric cell walls, this paper proposes a novel cellular structure with center-symmetric cell walls. The in-plane mechanical properties of this novel structure are explored through theoretical analysis and substantiated by both finite element simulations and experimental tests. Compared to the classic accordion honeycomb structure, the elastic modulus in the x-direction of the novel structure is reduced by an average of 58%, the strain amplification rate is increased by 122%, and the in-plane stiffness anisotropy is improved by 200%. These findings suggest that the proposed structure offers far superior stiffness anisotropy and large deformation potential, making it more suitable for morphing applications than the traditional ZPR cellular structures.

Carrier scattering and temperature characteristics of mobility and resistivity of Fe-doped GaN

Abstract The electron mobility and dark resistivity of Fe-doped semi-insulating GaN (GaN:Fe) are calculated over the temperature range from 10 K to 500 K by considering the impurities compensation mechanism and majority carrier scattering. The temperature characteristic curve of the mobility exhibits unimodality and the curve of resistivity decreases monotonically with rising temperature. The carrier scatterings induced by ionized impurities, acoustic deformation potential, piezoelectric, and polar optical phonons are analyzed. It is found that the mobility is determined by ionized impurity scattering, piezoelectric scattering, and polar optical phonon scattering in different temperature ranges, and the contribution of acoustic deformation potential scattering is negligible over the entire temperature range. Furthermore, the effects of concentrations of shallow donors and deep acceptors on the temperature characteristic curves of mobility and resistivity, the peak mobility and its corresponding temperature (peak temperature), and the mobility and resistivity at room temperature are discussed. Our simulation shows the calculation results agree very well with the reported experimental and theoretical results when the Fe-related level is selected as 0.58 eV below the conduction band edge. Understanding of thermal properties of dark resistivity and mobility can be useful for optimizing GaN:Fe-based electronic and photonic devices performance in different temperature regimes.

Deformation behavior of PST-TiAl bicrystals at 800 °C

PST (polysynthetic twinned) TiAl crystal exhibits excellent mechanical properties, and thus, it has been regarded as a critical candidate for turbine blades in the aero-engine industry. For the first time, the deformation behavior of PST-TiAl bicrystals with two different α2/γ lamellar orientations was studied in this work. Ti-46Al-6Nb bicrystals were cut from directionally solidified ingots, and three bicrystals of B1 (10°–14°), B2 (10°–19°), B3 (6°–75°) together with a single crystal of S1 (3°) were stretched at 800 °C. Then, the deformation behaviors, including fracture morphology, crack propagation, and deformation mechanism, were analyzed. Interestingly, these bicrystals show good high-temperature tensile performance, and their deformation behaviors seem to be very anisotropic. The findings indicate that the misorientation disparity in bicrystals primarily determines their deformation coordination capacity and corresponding mechanical performance. Subsequently, the difference in deformation orientation between the two lamellae significantly controls fracture behavior and deformation compatibility. High slip potential and abundant variant choices in γ phases are supposed to be beneficial for deformation capacity improvement. Meanwhile, the deformation potential of ordinary dislocation and superlattice dislocation slip systems in the α2 phase was also examined. Results show that the disparity in dislocation motion ability between γ variants gradually amplifies the advantages of the easy-mode phase in deformation through strain coordination, while mitigating the disadvantages associated with the difficult-mode phase. During further deformation, the relatively low bicrystal misorientation and small deformation capacity differences between the two lamellae determine high deformation coordination and improved performance. Overall, our work reveals that bicrystal deformation initiates at the relatively softer lamellae and proceeds to the harder lamellae, and its final comprehensive performance is determined by the deformation coordination capacity between the two lamellae.

Exploring photoconduction mechanisms in Lead‐Free Cs3Sb2I9 single crystal thin films

The future commercial advancement of lead-halide perovskites (LHPs) faces obstacles due to the existence of harmful lead and the inadequate stability associated with these materials. To tackle this challenge, we have prepared a Cs3Sb2I9 perovskite single-crystalline thin film (Cs3Sb2I9 device) using a technique based on the restricted evaporation of solvents in space, aiming for effective photodetection. The photodetector in the current study shows a responsivity (R) of around 111 mA/W and a detectivity (D∗) of approximately 3.7 × 1012 Jones. While these performance metrics are comparable to other photodetectors, there is a need for additional optimization to match the capabilities of commercial silicon and germanium-based counterparts. The examination of ultrafast transient absorption provides insights into the essential photophysics inherent in Cs3Sb2I9. The synergy between the deformation potential and the Fröhlich effect plays a crucial role in shaping electronic dynamics. This synergy leads to the self-trapping of charge carriers, resulting in the creation of localized polarons within the Cs3Sb2I9 lattice within just some picoseconds. The restriction of carrier mobility within Cs3Sb2I9 arises from the self-capturing and confinement of small polarons (SPs). Furthermore, it was noted that SPs in a localized state could undergo absorption into an elevated state (photon energy ⁓ 1.60 eV). This process effectively facilitates the charge carriers' mobilization to a more dispersed eigenstate. Our research provides essential comprehension into the light-induced processes of lead-free halide perovskites (LFHPs), offering valuable insights for their prospective use in optoelectronics as promising future semiconducting agents.

Unraveling the electronic properties in SiO2 under ultrafast laser irradiation

First-principles simulations were conducted to explore various electronic properties of crystalline SiO2 (α-quartz) under ultrafast laser irradiation. Employing Density Functional Perturbation Theory and the many-body (GW) approximation, we calculated the impact of thermally excited electrons on the electronic specific heat, electron pressure, effective mass, deformation potential, electron-phonon coupling and electron relaxation time of quartz, covering a wide range of electron temperatures, up to 100,000 K. We show that the electron-phonon relaxation time of highly-excited quartz becomes twice faster compared to low-excited states. The deformation potential, which dictates atomic displacement, has a non-monotonic behavior with a well-pronounced minimum at around 16,000 K (2.7 × 1021 cm−3 of excited electrons) where the bond ionicity of the Si-O starts decreasing followed by a cohesion loss at 35,000 K due to the pressure exerted by the excited electrons on the lattice. Consequently, our calculated data, illustrating the evolution of physical parameters, can facilitate simulations of laser-matter interactions and provide predictive insights into the behavior of quartz under experimental conditions.

Layer-dependent transport and optoelectronic properties in 2D all-inorganic Ruddlesden–Popper perovskite Cs2PbBr4

In recent years, two-dimensional (2D) all-inorganic Ruddlesden–Popper (RP) perovskites have attracted significant research attention. In this study, the electronic and carrier transport properties of 2D layered RP perovskite Cs2PbBr4 are studied by DFT calculations. The carrier mobility of the RP perovskite Cs2PbBr4 layers are studied based on deformation-potential (DP) theory. We found that the carrier mobility in 2D Cs2PbBr4 layers are enhanced as the number of layers increases. For trilayer Cs2PbBr4 the electron mobility reaches 7588.7 cm2V−1s−1, which is much higher than the widely studied bulk MAPbI3 (1500 cm2V−1s−1). In addition, the exciton binding energies are also calculated. Our work proves that the 2D RP perovskite Cs2PbBr4 layers are potential candidates for the photoelectronic devices applications.

Investigations for increasing the 3D-forming potential of high-density fiberboards

The trend in modern interior design leans towards curved and shaped surfaces. This cannot be achieved with flat materials without additional effort. Materials from renewable resources, such as wood-based materials, are material- and energy-intensively processed to enable larger deformations. Therefore, this study deals with methods to increase the deformation potential of adhesive-free, high-density fiberboards. One method is plasticizing in a saturated steam atmosphere, which is well known from the bending of solid wood. The second is the application of a special kerf pattern that geometrically increases the deformability. The combination of both methods was also investigated. Uniaxial tensile tests were performed to evaluate the deformation potential of the methods used. The strain along and transverse to the tensile direction, as well as the modulus of elasticity and Poisson’s ratio, were determined as results. All the methods investigated lead to an increase in the maximum strain along the tensile load: steaming by a factor of 2, kerf patterning by a factor of 4, and the combination by a factor of 10 as compared to solid fiberboard. The application of the kerf pattern causes an auxetic material behavior with a negative Poisson’s ratio. The combination of both methods reduces the modulus of elasticity by a factor of more than 100. Overall, the investigated methods are suitable for increasing the deformation potential of fiberboards with regard to the forming of 3D-shaped surfaces.