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Crystal surfaces play a pivotal role in governing various significant processes, such as adsorption, nucleation, wetting, friction, and wear. A fundamental property that influences these processes is the surface free energy, γ. We have directly calculated γ(T) for low-index faces of Lennard-Jones (LJ), germanium, and silicon crystals along their sublimation lines using the computational cleavage technique. Our calculations agree well with experimental values for Si(111) and Ge(111), highlighting the accuracy of the method and models used. For LJ crystals, we identified a premelting onset at Tpm = 0.75Tm, marked by a sharp increase in atom mobility within the second outermost surface layer. Notably, Tpm closely aligned with the endpoint of the LJ melting line at negative pressures, Tend = 0.76Tm. We hypothesize that the emergence and coexistence of a liquid film atop the LJ crystal at Tpm < T < Tm correspond to the metastable melting line under negative pressures experienced by stretched crystal surfaces. Furthermore, our study of thin LJ crystal slabs reveals that premelting-induced failure leads to recrystallization below the homogeneous freezing limit, offering a promising avenue to explore crystal nucleation and growth at extremely deep supercoolings. Finally, no evidence of premelting was detected in the model crystals of Ge and Si, which is consistent with the experimental observations. Overall, our findings offer valuable insights into crystal surface phenomena at the atomic scale. [ABSTRACT FROM AUTHOR]

The propagation of light beams in photovoltaic pyroelectric photorefractive crystals is modelled by a specific generalization of the nonlinear Schrödinger equation (GNLSE). We use a variational approximation (VA) to predict the propagation of solitary-wave inputs in the crystals, finding that the VA equations involve a dilogarithm special function. The VA predicts that solitons and breathers exist, and the Vakhitov–Kolokolov criterion predicts that the solitons are stable solutions. Direct simulations of the underlying GNLSE corroborates the existence of such stable modes. The numerical solutions produce both regular breathers and ones featuring beats (long-period modulations of fast oscillations). In the latter case, the Fourier transform of amplitude oscillations reveals a nearly discrete spectrum characterizing the beats dynamics. Numerical solutions of another type demonstrate the spontaneous splitting of the input pulse in two or several secondary ones. [ABSTRACT FROM AUTHOR]

Crystals constitute a variety of important materials from everyday life to cutting-edge fields. The properties of a crystal are determined by its structure, as demonstrated by physics theory, which is essential for understanding and designing materials. In recent years, deep learning-based methods have been proposed to predict crystal material properties and achieved satisfactory performance. However, these methods have not adequately accounted for the key composition of crystals, i.e., periodicity. To address this issue, we propose a periodicity aware crystal transformer (PACT), which uses hierarchical self-attention mechanisms to enforce periodicity constraints on the crystal structure. Specifically, it applies unit-wise self-attention and crystal-wise self-attention to ensure that the surroundings of atoms or unit cells at periodic distances are identical. Extensive benchmark experiments demonstrate that our proposed model exhibits superior performance, achieving an average improvement of 7.07% over previous methods. Additionally, ablation studies show both unit-wise self-attention and crystal-wise in the hierarchical self-attention mechanisms are effective in modeling the periodicity. [ABSTRACT FROM AUTHOR]

During the plastic deformation of metallic materials, part of expended mechanical energy diffuses as heat. The fraction of plastic work converted into heat is called the Taylor–Quinney Coefficient (TQC), which is often assumed to be a constant parameter of about 0.9. The remaining portion of the plastic work is called stored energy. The stored energy is known as the main driving force for dynamic or static recovery and recrystallization. Therefore, numerical predictions and experimental measurements of the stored energy and TQC are essential to optimize thermomechanical material processing. An adequate prediction of the stored energy and the TQC using existing crystal plasticity models in line with the experimental measurements remains a challenging problem. In this work, a thermodynamic class of crystal plasticity models is used to predict the stored energy and TQC of copper and aluminum single crystals. Then, the numerical stored energy predictions are extended to polycrystalline austenitic steel 316L and compared with the experimental measurements from the literature. An ad-hoc factor is introduced in the numerical expression of stored energy in order to compensate for the difference with the experimental measurement. To this end, the contributions of statistically stored dislocations (SSDs) and geometrically necessary dislocations (GNDs) for the stored energy prediction are analyzed to understand the physical origin of the ad-hoc factor. The contribution of GNDs to stored energy and enhanced hardening is accounted for by means of a strain gradient plasticity model. The present systematic finite element crystal plasticity simulations also include specific interface conditions at grain boundaries. The presented computational analysis indicates that, compared to the experiment, there remains dark energy in the evaluation of energy storage as predicted by the proposed thermodynamically consistent crystal plasticity framework. [ABSTRACT FROM AUTHOR]

Cylindrical Haynes 282 tensile specimens fabricated by laser powder bed fusion (L-PBF Haynes 282) have shown anomalous tensile deformation behavior, characterized by anisotropic lateral contraction and elliptical tensile fracture surfaces. In this work, crystal plasticity finite element simulations are conducted to explore the underlying mechanisms of such anomaly. Cylindrical models of grain aggregates are created according to the experimentally observed grain structure of L-PBF Haynes 282. The initial crystallographic orientations are assigned to generate a range of textures ranging from single crystalline to completely random. The evolution of the shapes and crystallographic textures of the simulated grain aggregates during tensile deformation have been analyzed and compared with experiments. It is found that the near-single crystal texture of L-PBF Haynes 282 is responsible for the deformation anomaly. Specifically, the simulated single crystal under tension along the [110] axis exhibits strong anisotropic lateral contraction; and the deformation of the model with random texture is symmetric about the loading axis. While both models evolve a relatively strong [111] pole along the loading axis during deformation, the orientation of the single crystal model splits about the [ 1 1 ¯ 0 ] direction and the random-texture model evolves into a strong fiber texture. When small, random misorientations are introduced into the single crystal model, the deformation anisotropy and texture evolution appear to be the intermediate of the two extreme cases; and resemble what is observed from the experiment. [ABSTRACT FROM AUTHOR]

We study the counting problem of BPS D-branes wrapping holomorphic cycles of a general toric Calabi-Yau manifold. We evaluate the Jeffrey-Kirwan residues for the flavoured Witten index for the supersymmetric quiver quantum mechanics on the worldvolume of the D-branes, and find that BPS degeneracies are described by a statistical mechanical model of crystal melting. For Calabi-Yau threefolds, we reproduce the crystal melting models long known in the literature. For Calabi-Yau fourfolds, however, we find that the crystal does not contain the full information for the BPS degeneracy and we need to explicitly evaluate non-trivial weights assigned to the crystal configurations. Our discussions treat Calabi-Yau threefolds and fourfolds on equal footing, and include discussions on elliptic and rational generalizations of the BPS states counting, connections to the mathematical definition of generalized Donaldson-Thomas invariants, examples of wall crossings, and of trialities in quiver gauge theories. [ABSTRACT FROM AUTHOR]

We introduce a class of 4-dimensional crystal melting models that count the BPS bound state of branes on toric Calabi-Yau 4-folds. The crystalline structure is determined by the brane brick model associated to the Calabi-Yau 4-fold under consideration or, equivalently, its dual periodic quiver. The crystals provide a discretized version of the underlying toric geometries. We introduce various techniques to visualize crystals and their melting configurations, including 3-dimensional slicing and Hasse diagrams. We illustrate the construction with the D0-D8 system on 4. Finally, we outline how our proposal generalizes to arbitrary toric CY 4-folds and general brane configurations. [ABSTRACT FROM AUTHOR]

Zigzag strip bundles are combinatorial models realizing the crystals B (∞) and the highest weight crystals B (λ) over quantum affine algebras U q (g) , and they are closely related with Nakajima monomials and Kashiwara embeddings of specific type. In this paper, we introduce new zigzag strip bundles for U q (g) , which we call reverse zigzag strip bundles in order to distinguish from the previous ones, and we give explicit 1-1 correspondences with the set of Nakajima monomials and the image of Kashiwara embedding which are different from those appeared in the study of the zigzag strip bundles. Another main result is to give different points of view about zigzag strip bundles and reverse zigzag strip bundles. Indeed, the previous 1-1 correspondences between the sets of zigzag strip bundles or reverse zigzag strip bundles, and the sets of Nakajima monomials or images of Kashiwara embeddings were determined based on the number of blocks in the columns of these strip bundles. In our work, we use the number of blocks in the rows of zigzag strip bundles and reverse zigzag strip bundles to provide characterizations of Nakajima monomials and images of Kashiwara embeddings that differ from the previous ones. That is, we give characterizations of Nakajima monomials and Kashiwara embeddings of 4 types. Further, we discuss the connection between zigzag strip bundles and reverse zigzag strip bundles. [ABSTRACT FROM AUTHOR]

Doping-induced local symmetry breaking of centrosymmetric molecular crystals endows them with piezoelectric and pyroelectric properties. In this work, we measured temperature dependences of pyroelectric and piezoelectric coefficients in α-glycine crystals single-doped by threonine and double-doped by threonine and alanine. We analyzed primary and secondary pyroelectric effects in these crystals and suggested a model of the dopant complexes related to the observed effects. [ABSTRACT FROM AUTHOR]

Additive manufacturing of as-build metal materials with laser powder bed fusion typically leads to the formations of various chemical phases and their corresponding microstructure types. Such microstructures have very complex shape and size anisotropic distributions due to the history of the laser heat gradients and scanning patterns. With higher complexity compared to the post-heat-treated materials, the synthetic volume reconstruction of as-build materials for accurate modelling of their mechanical properties is a serious challenge. Here, we present an example of complete workflow pipeline for such nontrivial task. It takes into account the statistical distributions of microstructures: object sizes for each phase, several shape parameters for each microstructure type, and their morphological and crystallographic orientations. In principle, each step in the pipeline, including the parameters in the crystal plasticity model, can be fine-tuned to achieve suitable correspondence between experimental and synthetic microstructures as well as between experimental stress–strain curves and simulated results. To our best knowledge, this work represents an example of the most challenging synthetic volume reconstruction for as-build additive manufacturing materials to date. [ABSTRACT FROM AUTHOR]

The phase‐field crystal model (PFC) describes crystal structures at diffusive timescales through a periodic order parameter representing the atomic density. One of its main features is that it naturally incorporates elastic and plastic deformation. To correctly interpret numerical simulation results or devise extensions related to the elasticity description, it is important to have direct access to the elastic field. In this work, we discuss its evaluation in classical PFC models based on the Swift–Hohenberg energy functional. We consider approaches where the stress field can be derived from the microscopic density field (i.e., the order parameter) and a simple novel numerical routine is proposed. By numerical simulations, we demonstrate that it overcomes some limitations of currently used methods. Moreover, we shed light on the elasticity description conveyed by classical PFC models, characterizing a residual stress effect present at equilibrium. We show explicitly and discuss the evaluation of the elastic fields in prototypical representative cases involving an elastic inclusion, a grain boundary, and dislocations. [ABSTRACT FROM AUTHOR]

Oxidative stress is a major risk factor for calcium oxalate nephrolithiasis. Reports suggest that oxidative stress response is induced in animals and humans with kidney stones. Keap1, Nrf2, and HO-1 are known as oxidative stress mediators. However, the association between oxidative stress response and stone formation is unclear. In this study, we analyzed oxidative stress response from the acute to the crystal formation phase when crystal formation was applied to renal crystal mice model and bioimaging mice and investigated the effect on crystal formation. In renal tissues, after glyoxylate administration, HO-1 increased for up to 6 h and returned to baseline at 24 h. This was observed following each daily dose until five days after the crystallization phase; however, the range of increase was attenuated. The possibility that Nrf2 activity influenced the number of crystals was considered in the experiment. Crystal formation increased in Nrf2-deficient mice and could be reduced by Nrf2 activators. In conclusion, the oxidative stress response via the Keap1-Nrf2 pathway may contribute to crystal formation. Particularly, this pathway may be a prospective target for drug development to prevent and cure nephrolithiasis. [Display omitted] • Expression of Nrf2 and Keap1 dynamically changes by time in renal stone models. • Genetic inactivation of Nrf2 promotes renal CaOx crystal formation. • Pharmacological activation of Nrf2 inhibits renal CaOx crystal formation. • Modulation of Nrf2 may have clinical applications in preventing kidney stones. [ABSTRACT FROM AUTHOR]

We discuss the Goldstone mode of skyrmion crystal in a model of two-dimensional ferromagnet with the Dzyaloshinskii–Moriya interaction in magnetic field. We use stereographic projection approach to construct skyrmion crystal and consider skyrmion displacement field. The small overlap of the individual skyrmion images restricts the potential energy to the interaction of nearest neighboring displacements. The closed form of the Goldstone mode dispersion is found and its dependence on the magnetic field is studied. We use semiclassical quantization to define the Green's function and show that the propagation of displacements through the crystal changes its tensorial form from anisotropic to isotropic one at large times. [ABSTRACT FROM AUTHOR]

Train vibrations can travel through the track, tunnel structure, and surrounding strata as well as into the structure of buildings near tunnels, where they can be radiated as low-frequency vibration waves and noises inside the building. Low-frequency vibration reduction is a major challenge for vibration control technology. Herein, the new phononic-like crystal metaconcrete material was invented to make the track bed for decreasing vibration induced by trains because it can open low-frequency bandgaps to reduce the low-frequency vibration in actual subway engineering. First, the original phononic-like crystal model was optimized to improve the vibration reduction effect for low-frequency bandgaps. Second, the metaconcrete track beds were conducted according to the new phononic-like crystal model based on the vibration reduction need. Finally, the metaconcrete track beds were installed in the Ning-Ju line of Nanjing Metro in Nanjing, China, and the vibration reduction effect was monitored. The monitoring results in the Ning-Ju line demonstrate that the new phononic-like crystal structure metaconcrete track bed has excellent vibration reduction performance for rail transportation. [ABSTRACT FROM AUTHOR]

The lattice parameters of A2XY6 (A = K, Cs, Rb, and Tl; X = tetravalent cation; Y = F, Cl, Br, and I) cubic crystals play significant roles in designing materials for specific technological applications and uniquely describe the material crystal structure. Despite the importance of its lattice parameters, the experimental determination of these parameters requires special sophisticated equipment, while the first principle calculation consumes appreciable time and might need complex software packages. The existing empirical relation in the literature is characterized by large percentage deviation, and the recently proposed machine learning support vector regression method cannot be empirically implemented on new compounds. This present work fills the research gap through the development of empirical relation between the lattice parameters, electronegativity and ionic radii of the constituting ions using extreme learning machine (ELM) with the grid search (GS) hyper-parameters optimization method. The proposed model is developed through the analysis of atomic structural properties of 85 crystals that serve as representatives of the A2XY6 group. On the basis of a mean absolute percentage error, the developed GS-ELM model outperforms the existing Brik and Kityk [J. Phys. Chem. Solids 72(11), 1256–1260 (2011)] model with a percentage improvement of 58.37%, while it performs better than Alade et al. [J. Appl. Phys. 127(1), 15303 (2020)] model with the percentage enhancement of 37.90%. The outstanding performance of the proposed GS-ELM model coupled with its ease of implementation would be of great significance by enhancing the search for new materials tailored to targeted application and preventing lattice constant mismatch in thin film fabrication. [ABSTRACT FROM AUTHOR]

Electron–phonon coupling plays a central role in the transport properties and photophysics of organic crystals. Successful models describing charge- and energy-transport in these systems routinely include these effects. Most models for describing photophysics, on the other hand, only incorporate local electron–phonon coupling to intramolecular vibrational modes, while nonlocal electron–phonon coupling is neglected. One might expect nonlocal coupling to have an important effect on the photophysics of organic crystals because it gives rise to large fluctuation in the charge-transfer couplings, and charge-transfer couplings play an important role in the spectroscopy of many organic crystals. Here, we study the effects of nonlocal coupling on the absorption spectrum of crystalline pentacene and 7,8,15,16-tetraazaterrylene. To this end, we develop a new mixed quantum–classical approach for including nonlocal coupling into spectroscopic and transport models for organic crystals. Importantly, our approach does not assume that the nonlocal coupling is linear, in contrast to most modern charge-transport models. We find that the nonlocal coupling broadens the absorption spectrum non-uniformly across the absorption line shape. In pentacene, for example, our model predicts that the lower Davydov component broadens considerably more than the upper Davydov component, explaining the origin of this experimental observation for the first time. By studying a simple dimer model, we are able to attribute this selective broadening to correlations between the fluctuations of the charge-transfer couplings. Overall, our method incorporates nonlocal electron–phonon coupling into spectroscopic and transport models with computational efficiency, generalizability to a wide range of organic crystals, and without any assumption of linearity. [ABSTRACT FROM AUTHOR]

The bendability of extruded profiles of an age hardenable aluminum alloy is investigated using mechanical tests on flat tensile specimens and bending specimens. Two profile geometries are considered, where the profiles exhibit different grain structures. The microstructure of the profiles in terms of the crystallographic texture and constituent particles is otherwise comparable. While the tensile properties are not that different for the two profiles, their bendability is strongly dependent on the grain structure and is about twice as high for one profile than for the other. A newly proposed coupled damage and single crystal plasticity model is used in finite element analyses of the mechanical tests to investigate the influence of the grain structure on the bending behavior, and the numerical results are compared to the experimental tests. The crystallographic texture and the grain morphology of the profiles, found by the electron back-scatter diffraction technique, are explicitly represented in the finite element models. The crystal plasticity simulations capture the difference in the bendability of the two profiles, and in agreement with the experiments predict a considerably higher bendability for one of the profiles. It is found that the grain structure affects the shear band formation in these profiles, but also the local texture where the shear bands are located is important for crack initiation and propagation as grains with certain crystallographic orientations may have a higher fracture resistance. [ABSTRACT FROM AUTHOR]

Objective: Particle shape can have a significant impact on the bulk properties of materials. This study describes the development and application of machine-learning models to predict the crystal shape of mefenamic acid recrystallized from organic solvents. Methods: Crystals were grown in 30 different solvents to establish a dataset comprising solvent molecular descriptors, process conditions and crystal shape. Random forest classification models were trained on this data and assessed for prediction accuracy. Results: The highest prediction accuracy of crystal shape was 93.5% assessed by fourfold cross-validation. When solvents were sequentially excluded from the training data, 32 out of 84 models predicted the shape of mefenamic acid crystals for the excluded solvent with 100% accuracy and a further 21 models had prediction accuracies from 50–100%. Reducing the feature set to only solvent physical property descriptors and supersaturations resulted in higher overall prediction accuracies than the models trained using all available or another selected subset of molecular descriptors. For the 8 solvents on which the models performed poorly (< 50% accuracy), further characterisation of crystals grown in these solvents resulted in the discovery of a new mefenamic acid solvate whereas all other crystals were the previously known form I. Conclusions: Random forest classification models using solvent physical property descriptors can reliably predict crystal morphologies for mefenamic acid crystals grown in 20 out of the 28 solvents included in this work. Poor prediction accuracies for the remaining 8 solvents indicate that further factors will be required in the feature set to provide a more generalized predictive morphology model. [ABSTRACT FROM AUTHOR]

The Czochralski (CZ) process is the core technology for producing semiconductor silicon monocrystalline (SMC), and it is a complex batch process. However, the crystal growth rate and crystal diameter, which are key quality indicators, are difficult to detect directly online, and the offline calculation process lags seriously, which easily causes blind crystal quality control. Therefore, this paper proposes a data-driven and mechanism-based hybrid model for semiconductor SMC quality variables prediction in the CZ process. Firstly, a data-driven model JITL-SAE-ELM based on just-in-time learning (JITL) fine-tuning strategy is proposed. This model is used to solve the nonlinear and time-varying relationship of the energy transfer process in the CZ process that cannot be accurately described by traditional mechanism models. Here, the SAE-ELM model integrates a stacked autoencoder (SAE) and an extreme learning machine (ELM), which are used to deeply capture the nonlinear and time-varying features of process data. Secondly, according to the hydrodynamics and geometric behavior, a crystal pulling dynamic mechanism model based on the crystal growth mechanism is constructed, which avoids the complicated heat transfer link. Further, considering the unmodeled dynamics caused by model parameter uncertainty during the combination of the energy transfer model and crystal pulling dynamic mechanism model, a crystal diameter compensation model SAE-ELM was developed to improve the prediction accuracy of the CZ process hybrid model. Finally, an industrial data experiment based on a CZ monocrystal furnace illustrates the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a variational polycrystalline model in finite crystal plasticity with one active slip system and rigid elasticity. The task is to determine inner and outer bounds on the domain of the constrained macroscopic elastoplastic energy density, or equivalently, the affine boundary values of a related inhomogeneous differential inclusion problem. A geometry‐independent Taylor inner bound, which we calculate directly, follows from considering constant‐strain solutions to a relaxed problem in combination with well‐known relaxation and convex integration results. On the other hand, we deduce outer bounds from a rank‐one compatibility condition between the affine boundary data and the microscopic strain at the boundary grains. While there are examples of polycrystals for which the two above‐mentioned bounds coincide, we present an explicit construction to prove that the Taylor bound is nonoptimal in general. [ABSTRACT FROM AUTHOR]

The justification of the applicability of constitutive models to exploring technological processes requires a detailed analysis of their performance when they are used to describe loadings including the complex loading mode that is characteristic of these processes. This paper considers the effect of equivalent stress overshooting after the strain-path changes known to occur in metals and alloys. The macrophenomenological and multilevel models, which are based on crystal plasticity, account for this effect by applying anisotropic yield criteria at the macro- and mesolevels, respectively. We introduce a two-level constitutive statistical inelastic deformation model (identified for aluminum) that incorporates the popular simple phenomenological anisotropic hardening law for describing the behavior of FCC polycrystals. The results of the numerical simulation are in satisfactory agreement with existing experimental data. Statistical analysis of the motion of a mesostress in the stress space on the crystallite yield surface is performed. The obtained data are compared with the results found using the isotropic hardening law. The results clarify the simulation details of statistical crystal plasticity models under loading with strain-path changes in materials and demonstrate their suitability for describing the processes under consideration. [ABSTRACT FROM AUTHOR]

Crystal phase quantum dots are formed by vertically stacking zinc-blende and wurtzite phases during nanowire growth. In this work, we show, using an atomistic many-body approach, that crystal field splitting in the wurtzite phase, as well as spontaneous polarization originating from the phase interfaces, will strongly affect the properties of lowest hole states in InP crystal phase quantum dots, and in turn the excitonic optical spectra. We also show that the artifact-free modeling of crystal phase quantum dots should incorporate any additional potentials on equal footing with the electron-hole interaction. In this paper, we discuss a reliable theoretical framework that can be applied to investigate the electronic and optical properties of InP-based crystal phase quantum dots. The importance of accurate excitonic calculations for such systems is highlighted in view of their potential applications in nanowire photonics, yet further research is necessary for bringing theory and experiment in agreement. [ABSTRACT FROM AUTHOR]

• A two-scales macro-micro method is developed to model the materials undergo necking and failure, in order to determine the material intrinsic properties at microstructural scale. • A macro rate-dependent anisotropic plasticity and damage model is proposed that well captured the necking strain, total elongation and reduction of area at various applied strain rate. • The 'true' stress-strain behaviors at the necking zone are identified and transferred to the crystal plasticity microstructural model, which then captures the underlying heterogenous deformation and damage in the microstructure during the necking, and reveals 'true' microstructure-properties relationship. This work develops a two-scales macro-micro approach to address the challenge in calibrating crystal plasticity microstructural models when samples undergo necking prior to fracture. The crystal plasticity models are crucial for predicting the materials' plastic deformation and failure at the microstructure level, identifying the materials' intrinsic properties as well as investigating the microstructure-properties relationships. However, after necking occurs, the experimentally measured stress-strain curves fail to reflect the materials 'true' stress-strain behavior and cannot be directly fitted into crystal plasticity models. The proposed macro-micro approach employs a top-down strategy to address this challenge, which has been studied with experimental tests on precipitation-strengthened Ni-based superalloy Haynes® 282®. In this approach, a macro rate-dependent anisotropic plasticity model with Voce-type hardening and Rice-Tracey damage law is first utilized to model the deformation and failure of the tensile bar, and calibrated by matching the stress-strain curves, necking strain, and reduction of area. Especially, to match the testing results under different applied strain rates, the rate-sensitivity parameter m and saturation stress in the elasticity model are modified to incorporate dependence on the local strain rate. Then, the 'true' stress-strain behaviors are extracted from the necking zone of the macro-model, which are used to calibrate a micro-model with explicit microstructures and governed by an extended crystal plasticity law. The consistency between the micro-model and macro-model are enforced during calibration. The calibration outcomes from the crystal plasticity model elucidate the materials intrinsic properties for slip, hardening, and failure, which is vital for further investigations into the microstructure-properties relationship and for accurate prediction of the material behavior under various test and service conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The most stable defect compensation model is constructed using lattice dynamics. • H i is bonded to an O ion forming hydroxyl (0.99 Å) in both systems. • (V K + H i). have large formations and are therefore unstable. • It is expected to produce absorption with peaks around 167 nm and 179 nm. • It is expected to produce luminescence with peaks around 623 nm and 867 nm. The electronic structures, defect formations, defect transition levels and optical properties for V K + H i defect models in KDP crystals have been studied based on DFT. Lattice dynamics methods give the most reasonable compensation mechanism for V K , namely compensation with the third-nearest H i neighbor from V K for the paraelectric (PE) phase and compensation with the fourth-nearest neighbor H i from V K for the ferroelectric (FE) phase. The defect formation energies indicate that the (V K + H i) x (The superscript represents the charged state, the 'x' represents neutral, '" represents −1 charge state and '.' represents +1 charge state.) is the main defect type in this kind of defect cluster and a self-trapped electron is located at H i in the (V K + H i)′ system. For (V K + H i) x system, one electron is accommodated in V K. There is not a new defect state in the band gap. The H i bonds with the O ion (0.99 Å) form a hydroxyl. For (V K + H i)′ system, the hydroxyl is broken, the H i exists in an atomic form and introduces new defect states in the band gap. As the large relaxation energy leads to a large Huang-Rhys factor, the Stokes red shifts will significantly affect the optical properties. A broad ultraviolet (UV) absorption band and emission band range from UV to visible are obtained originating from the defect cluster. We believe that the far-violet absorption peaks (167 nm and 179 nm) caused by defect cluster V K + H i can significantly impact the optical damage threshold of the KDP. [ABSTRACT FROM AUTHOR]

• High-fidelity representative volume elements（RVEs）for ultra-high strength steel have been established. • Deformation strain of the UHSS is non-uniform with two distinct types of deformation bands. • The deformation inhomogeneity and fracture formation location are affected by the initial orientation of the grains. • The α-fiber texture enhances the deformation inhomogeneity of ultra-high-strength steel. Understanding deformation inhomogeneity and the formation mechanism of crack are crucial for fully exploiting the potential of ultra-high strength steel (UHSS). In this paper, the deformation inhomogeneity and microscopic crack formation mechanism of UHSS were investigated by combining high-fidelity crystal plasticity models with microscopic experiments. The simulation results at grain level show that the deformation strain of the UHSS is non-uniform, characterized by distinct deformation bands. A broad deformation band extends between multiple grains at an angle of approximately 40 degrees to the rolling direction, while a sharp deformation band is observed within a single grain. These features are intricately linked to the initial orientation (Taylor factor) distribution of the grains and their rotational behavior. The locations with greater Taylor factor deviations become potential crack initiation sites. In addition, as the deformation proceeds, the α-fiber reinforcement exacerbates the deformation inhomogeneity of the UHSS. [ABSTRACT FROM AUTHOR]

Size effect has a significant influence on the accuracy of two key factors of parameters and models in crystal plasticity simulation. This study introduces a parameter identification method that considers the indentation size effect, determining the initial slip resistance of IN625 alloy. Based on the identified parameters and utilizing the integral point traversal method, a grain boundary affected zone (GBAZ), whose strength field related to the distance to the grain boundary (GB) is introduced into the polycrystalline microstructure to represent the hindering effect of GBs on dislocations. This method effectively predicts the Hall-Petch effect and strain hardening behavior of IN625 alloy. The research reveals that dislocation pile-ups primarily concentrate in small grain clusters within the material. In fine-grained microstructures, a large volume fraction of GBs promotes dislocation pile-ups, reducing the mean free path of dislocations, leading to an increase in dislocation multiplication rate, and consequently, enhancing the strain hardening rate. An increase in GBAZ thickness results in a large stress level within the material, accompanied by a decrease in the homogeneity of stress distribution. However, the sensitivity of strain to GBAZ thickness is found to be low. The method proposed in this work holds significant applicative relevance in parameter calibration and prediction the mechanical properties of polycrystalline materials. • A modified method for identifying crystal plasticity parameters was proposed. • There is a strong linear relationship between strength and hardness at the micro-nano scale. • An explicit grain boundary affected zone was introduced into the model. • The Hall-Petch effect and strain hardening behavior of IN625 alloy was predicted. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct cyclic analysis combined with a phenomenological crystal plasticity model is used to simulate the cyclic behaviour of L-PBF 316L SS and to predict its shakedown limit. • Direct cyclic analysis accurately and efficiently computes the stable cyclic response of the material. • The critical combination of a defect and an unfavourable surrounding grain orientation can significantly reduce the shakedown limit. • Various local heterogeneous responses around a defect in the material L-PBF 316L SS were observed by simulation and it is suggested that they may be correlated with the scatter of the fatigue strength. The fatigue performance of Laser Powder Bed Fusion manufactured 316L stainless steel is critical for cyclic loading applications. Additive manufacturing of 316L produces a characteristic microstructure consisting of grains with a fine cellular structure within. This microstructure shows a comparatively high fatigue strength combined with a high defect tolerance. The purpose of this paper is to numerically analyse the local response of this microstructure to cyclic loading and, in particular, the joint action between lack of fusion defects and the surrounding grain structure. The traditional incremental analysis method for polycrystalline alloys is computationally expensive. Therefore, a direct cyclic analysis combined with a phenomenological crystal plasticity model is used in this work to predict the stable cyclic response of the material, resulting in a much lower computational cost. Three statistically equivalent representative volume elements are generated. The considered crystal plasticity parameters are calibrated using experimental tensile stress–strain curves. The comparison with incremental analysis demonstrates the accuracy and efficiency of the proposed method. The shakedown limit, based on the maximum load that allows the convergent cyclic response, significantly depends on the local grain orientation around lack of fusion defects, revealing a reason for the large scatter in the fatigue strength. [ABSTRACT FROM AUTHOR]

Sila‐ibuprofen is a new potential nonsteroidal anti‐inflammatory drug which deviates from its parent ibuprofen in terms of the electrostatic potential around the carbon/silicon‐switched C/Si—H group. Therefore, sila‐ibuprofen is more water soluble and has a lower melting enthalpy. However, its binding and inhibition properties of cyclooxygenases appear to be very similar to regular ibuprofen. Therefore, in this study, intermolecular interactions and interaction densities of both ibuprofen and sila‐ibuprofen in their biologically active forms, i.e. deprotonated and as the pure S‐enantiomers are investigated. Quantum‐crystallographically refined salts with argininium and 1‐phenylethan‐1‐amoninium (PEA) counter‐cations as crystalline models of the interactions with the guanidine functional group of arginine inside cyclooxygenases are presented. The similarities and differences between the polarization of ibuprofen and sila‐ibuprofen in the crystal, enzyme, solvent and isolated environments are discussed based on quantum‐chemical calculations. For the explicit crystal and enzyme environments, specifically, molecular dynamics simulations starting from the crystal models were combined with QM/MM calculations. [ABSTRACT FROM AUTHOR]

We studied the fracture strain of polycrystal ɑ-iron at three different hydrogen concentrations and for three crystal sizes with molecular dynamics simulations (MDs). As the hydrogen concentration increases, a fine crystal model's fracture resistance is prone to below a comparatively coarse grain model. This finding elucidates that the most vulnerable area can alter from coarse grain zone to fine-grain zone in the welding heat-affected zone (HAZ) with the effect of hydrogen. A simplified model is thus built to predict the strain energy increment in different crystal size systems caused by the introduction of hydrogen atoms. This strain energy increment is not equal to the fracture energy reduction induced by the same amount of hydrogen insertion, demonstrating that elastic volume expansion of grain boundary (GB) caused by hydrogen is not the determining mechanism of intergranular failure. The density of triple or multi-junctions of GBs, which is typically dependent on the volume fraction of GBs, is the crucial factor for intergranular failure caused by hydrogen embrittlement. [Display omitted] • The GB expansion and the concentration of H are linearly correlated. • Fine crystals be more susceptible to H-induced fracture than coarse crystal. • Multi-junctions of GBs are most sensitivity to hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

In this work, we present the cubic crystal elastic constants of a fully crystallized white dwarf stellar core. Elastic constants were calculated utilizing modal analysis of three-dimensional single-layer and stratified multi-layer crystalline core models. The models were generated using a Fortran based forward calculation algorithm in combination with a finite element modeling software program and were based on the parameters associated with the pulsating crystallized white dwarf BPM 37093. The calculated cubic crystal elastic constants, in comparison with elastic parameters of theoretical Coulomb crystal models of white dwarf matter, differed by, at most, a few orders of magnitude. In addition, the crystallized stellar core elastic parameters produced associated vibrational modes and frequencies that are consistent with the periodicity observed in BPM 37093. [ABSTRACT FROM AUTHOR]

The out-of-plane optical constants of monolayer two-dimensional materials have proven to be experimentally elusive. Owing to their reduced dimensionality, optical measurements have limited sensitivity to these properties which are hidden by the optical response of the substrate. Therefore, there remains an absence of scientific consensus on how to correctly model these crystals. Here we perform an experiment on the optical response of a single-layer two-dimensional crystal that addresses these problems. We successfully remove the substrate contribution to its optical response by a step deposition of a monolayer crystal inside a thick polydimethylsiloxane prism. This allows for a reliable determination of both the in-plane and the out-of-plane components of its surface susceptibility tensor. Our results prescribe one clear theoretical model for these crystals. This precise characterization of their optical properties will be relevant to future progresses in photonics and optoelectronics with two-dimensional materials. Experimental testing of the expected linear optical anisotropy of 2D crystals, arising from their finite thickness, have so far been complicated by substrate contributions. Here, immersion of monolayer samples in a low-refractive-index polymer allows more accurate determination of their optical constants. [ABSTRACT FROM AUTHOR]

Photomechanical molecular crystals are a family of mechanically responsive materials that have been recognized as a novel type of actuator. The actuation properties of photomechanical crystals should be characterized. However, deflection and force, which are crucial for actuators, are dependent on experimental conditions such as light intensity and crystal size, and thus the number of combinations under different conditions is infinite. This causes difficulty in obtaining the relationship between the experimental conditions and actuation outputs. To solve this problem, this paper presents a machine learning-based regression approach for modeling the deflection and force of a photo-bending crystal. The deflection and force were experimentally measured for various light intensities and crystal sizes. These time-series data of deflection and force were represented by feature values via exponential fitting for bending and unbending processes. The features of the maximum value and speed of deflection and force were analyzed by polynomial regression and variable selection. Through this process, the most fitted models were constructed for deflection and force and most of them were interpreted by material mechanics. This statistical strategy will potentially be applied to control or optimize other functions of stimuli-responsive crystals. [ABSTRACT FROM AUTHOR]

The growth process of Czochralski (Cz) silicon single crystal is a dynamic time-varying system with nonlinearity, strong coupling, large hysteresis, and uncertain model. Traditional model-based control methods are difficult to achieve satisfactory crystal growth control effects, and it is difficult to ensure that the crystal quality meets the actual process requirements. Therefore, from the perspective of data-driven modeling and control, this paper proposes a model predictive control method for the crystal growth process with a V/G soft-sensing model for measuring crystal quality. First, because the V/G value to measure crystal quality is difficult to obtain directly, a hybrid variable weighted stacked autoencoder random forest (HVW-SAE-RF) soft-sensing model based on data-driven V/G value is established. Here, the HVW-SAE is used to extract the deep quality-related features of the measurable process data, and the RF is used for the regression prediction of the SAE output layer; Second, using the dual closed-loop control strategy, the inner loop is based on the HVW-SAE-RF soft-sensing model of the V/G value, and the predictive PI control method is used to control the V/G value closely related to the crystal quality within a reasonable range, and the outer loop based on real-time estimation of V/G values to achieve nonlinear model predictive control (NMPC) of crystal diameter; finally, the effectiveness of the proposed method is verified based on the industrial production process data of silicon single crystal. [ABSTRACT FROM AUTHOR]

Model-based control methods do not produce satisfactory control results with the batch process control of Czochralski (CZ) silicon monocrystalline with complex nonlinearity, large delay, and time-varying dynamics. Therefore, this paper proposes a data-driven model-free adaptive iterative learning control method (MFAILC) to achieve precision control of the batch process. Firstly, to improve the accuracy of the data-driven model, a novel deep learning model for crystal growth process is established by combining a stacked autoencoder (SAE) and a long short-term memory network (LSTM) to extract the working condition information and the dynamic timing features in process data. Traditional model-based control methods are limited by the difficulties in modeling and by the unmodeled dynamics. So, to overcome this problem, the heater controller and the crystal puller controller are designed, based on the iterative dynamic linearization technology, to ensure that the silicon monocrystalline batch manufacturing process always maintains precision control. Also, the discrete-time extended state observer (ESO) is introduced to compensate for the influence of disturbances, to improve the robustness of the control system. Finally, the efficacy of the proposed method is verified by applying it for the predictive modeling and batch control of thermal field temperature and crystal diameter during crystal growth. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mathematical model for crystallization in a tubular crystallizer was developed. • Nucleation has been shown to control the kinetics of benzoic acid crystallization. • Breakage term has been introduced to population balance equation. • Appropriate CSD span was obtained with size-independent crystal growth model. Since crystallization is one of the leading separation, isolation, and purification methods, the present mechanistic work investigated its continuous approach, presenting the precipitation of the benzoic acid molecules in a plug flow crystallizer. In some crystallization experiments, seeding was used in an attempt to eliminate spontaneous nucleation phenomena to allow better control over crystal size distribution by promoting crystal growth. At the same measurement time, a systematic mathematical model, based on mass varying expressions, kinetics and particle balance equations, was applied to predict the properties of the product crystals. Benchmarking the results of validation experiment, the established physical representation sufficiently described operation, which is confirmed by comparing various experimentally and theoretically determined process and product characteristics. Since liquid static mixers were used, a nearly perfect defined regime formation was achieved, which could be demonstrated by comparing simulated, calculated and experimentally-determined differential functional size distribution; therefore, a developed general morphology independent modelling could be built to optimise unit satisfactorily. Although crystallization of benzoic acid was investigated, the methodology can be easily applied to crystallization of other active pharmaceutical ingredients. The utilization of process analytical technologies and simulations can aid optimisation, intensification and automation, which can improve the quality of formulations. [ABSTRACT FROM AUTHOR]

The structures of Aspergillus oryzae α-amylase were determined in a tetragonal crystal, having one molecule as asymmetric unit, and a monoclinic crystal with two molecules as asymmetric unit. Both crystal forms were obtained from trace contaminants of an old commercial lipase preparation. Structures were determined and refined to 1.65 Å and 1.43 Å resolution respectively. The latter crystal has a non-crystallographic (NCS) twofold axis within the asymmetric unit. Glycosylation at Asn197 is evident, and in the tetragonal crystal can be seen to include three, partially disordered sugar residues following the initial N -acetyl glucosamine (NAG). Superposition of the tetragonal crystal model on the α-amylases from Bacillus subtilis (PDB: 1BAG), pig pancreas (PDB: 3L2L), and barley (PDB: 1AMY), show a high degree of coincidence, particularly for the (β/α) 8 -barrel domains, and especially within the active site. Using this structural agreement between amylases, we extrapolated the binding model of a six residue, limit dextrin found in pig pancreas α-amylase to the A. oryzae enzyme model, which predicts substrate interacting amino acid residues. [ABSTRACT FROM AUTHOR]

Interband three-photon optical transitions in crystals of the InSb and type are classified, and the spectral dependence of some optical transitions is analyzed. The coefficient of linear-circular dichroism of interband three-photon absorption in a crystal in the Kane model is calculated. [ABSTRACT FROM AUTHOR]

Titanium alloys exhibit complex microstructures containing heterogeneities at different lengthscales. Although the size of primary α grains is typically in the micrometer range, processing of α / β titanium alloys can introduce millimeter long clusters of α particles with the same or nearly the same crystallographic orientation. These microtextured regions (MTRs), also called macrozones, are known to have a detrimental influence on the alloy performance under cyclic loadings. Recent studies evidenced an effect of the degree of microtexture on the yield strength of polycrystalline aggregates. In the present work, numerical simulations of the macroscopic response of large 3D aggregates containing MTRs with different shapes and sizes were performed using a fast Fourier transforms-based crystal plasticity model. Both macroscale response and microscale stress and strain fields were found affected by the presence of MTRs and their features. A mechanistic understanding of the relation between the mechanical behavior at different scales is discussed to obtain insights into the, still poorly understood, effect of microtextured regions on tensile properties. [ABSTRACT FROM AUTHOR]

The simple model that can describe structure and charge ordering in complex doped organic crystals is proposed. We consider the quasione-dimensional model of a crystal with chains (stacks) of flat BEDT-TTF molecules. In a chain of large molecules, small molecules fill every space between large molecules. The interaction between all molecules is described by the Lennard-Jones potential. It is shown that the small dopant molecules are in the double-well potential. It is shown that in case of the electrically neutral molecules at low temperatures, there is a fluctuating structural ordering: the small molecules group in pairs near a large molecule, and the lattice period in the fluctuation domain doubles. The structure of the boundary between the fluctuation domains is defined. In case of the charged molecules, correction to electric dipole interaction makes the system essentially three-dimensional, and there is ferroelectric ordering in a chain and an antiferroelectric one between the chains. Structure of the charge domains and domain boundaries are described. [ABSTRACT FROM AUTHOR]

Nonlinear elastic models are widely used to describe the elastic response of crystalline solids, for example, the well-known Cauchy–Born model. While the Cauchy–Born model only depends on the strain, effects of higher-order strain gradients are significant and higher-order continuum models are preferred in various applications such as defect dynamics and modeling of carbon nanotubes. In this paper we rigorously derive a higher-order nonlinear elasticity model for crystals from its atomistic description in one dimension. We show that, compared to the second-order accuracy of the Cauchy–Born model, the higher-order continuum model in this paper is of fourth-order accuracy with respect to the interatomic spacing in the thermal dynamic limit. In addition we discuss the key issues for the derivation of higher-order continuum models in more general cases. The theoretical convergence results are demonstrated by numerical experiments. [ABSTRACT FROM AUTHOR]

The work is devoted to the description of unsteady thermal processes in low-dimensional structures. To obtain the relationship between the microscopic and macroscopic descriptions of solids, it is necessary to understand the heat transfer mechanism at the micro-level. At the latter, in contrast to the macro-level, analytical, numerical, and experimental studies demonstrate significant deviations from the Fourier's law. The paper bases on the ballistic heat transfer model, according to which the heat is carried by the thermal waves. This effect can be applied, for example, to signal transmission and heat removal problems. The influence of non-nearest neighbors on processes in discrete media, as well as processes in polyatomic lattices, is investigated. To describe the evolution of the initial thermal perturbation, the dispersion characteristics and group velocities in one-dimensional crystal are analyzed for (i) a diatomic chain with variable masses or stiffnesses and for (ii) a monatomic chain with regard for interaction with second neighbors. A fundamental solution to the heat distribution problem for the corresponding crystal models is obtained and investigated. The fundamental solution allows to obtain a description of waves traveling from a point source, and can serve as the basis for constructing all other solutions. In both cases, the solution consists of two thermal fronts moving one after another with different speeds and intensities. Quantitative estimates of the intensity of the thermal wave front are given, and the dynamics of changes in the velocities and intensities of the waves depending on the parameters of the problem is analyzed. Thus, a simple method for estimating the wavefronts intensity is proposed and tested on two models. These results can be used to identify and analyze those parts of the wave processes that are of interest in terms of interpretation of the effects observed in the experiments. [ABSTRACT FROM AUTHOR]

Metaconcrete, as a new type of composite material with vibration attenuation characteristics, is formed by replacing traditional coarse aggregates with a heavy metal core wrapped with an elastic soft coating and mixing with cement mortar. However, due to the high bandgap frequency and narrow bandgap width, it is greatly limited in the engineering application of low frequency vibration control. In order to broaden the range and number of elastic wave bandgap of metaconcrete materials and solve the problem of low frequency vibration, a novel three-component cement-based phononic-like crystal model is proposed based on local resonance theory, and phononic-like crystal metaconcrete vibration reduction material is developed accordingly. Secondly, the band structure, bandgap mechanism, and frequency response function of the phononic-like crystal metaconcrete are calculated and analyzed, and indoor tests of the phononic-like crystal metaconcrete are conducted. Finally, a phononic-like crystal metaconcrete subway track bed is prepared using the developed phononic-like crystal metaconcrete material, and applied to the practical subway engineerings to solve the low frequency vibration problem generated during subway operation. The results show that the phononic-like crystal metaconcrete opens 6 low frequency bandgaps in the frequency range of 200 Hz, and the attenuation values are mostly above 10 dB in the frequency range of the bandgap, and the attenuation effect is good. Meanwhile, the on-site monitoring results show that the phononic-like crystal metaconcrete subway track bed has good low frequency vibration reduction effect in the 200 Hz frequency range. The maximum value of the one-third octave insertion loss of the tunnel wall is 13.22 dB, the maximum vertical Z-vibration level difference of the tunnel wall is 5.052 dB, and the maximum vertical frequency division vibration level difference of the tunnel wall is 5.926 dB. The maximum value of the vertical frequency division vibration level difference in the frequency range of 4–200 Hz is 13.87 dB, and the average value is 5.74 dB. The relevant research results of this paper provide a new technical approach to solve the problem of low frequency vibration in subway engineering and other engineering construction, breaking through the traditional vibration reduction control technology of civil engineering structures, and providing new idea and method for long-term vibration reduction and application of engineering structures. • This paper develops phononic-like crystal metaconcrete vibration reduction material. • The material can open multiple low frequency vibration reduction bandgaps. • The material is used to prepare a new type of subway vibration reduction track bed. • The subway track bed has remarkable low frequency vibration reduction performance. [ABSTRACT FROM AUTHOR]

Microcrystal electron diffraction (MicroED) is a powerful tool for determining high-resolution structures of microcrystals from a diverse array of biomolecular, chemical, and material samples. In this study, we apply MicroED to DNA crystals, which have not been previously analyzed using this technique. We utilized the d(CGCGCG) 2 DNA duplex as a model sample and employed cryo-FIB milling to create thin lamella for diffraction data collection. The MicroED data collection and subsequent processing resulted in a 1.10 Å resolution structure of the d(CGCGCG) 2 DNA, demonstrating the successful application of cryo-FIB milling and MicroED to the investigation of nucleic acid crystals. [Display omitted] • MicroED was applied to determine the structure of DNA • A d(CGCGCG) 2 DNA duplex was used as a model target and its 1.1 Å structure was determined • Cryo-FIB milling was employed to create thin crystalline lamella for MicroED • This study demonstrates the applicability of MicroED for nucleic acid crystallography Haymaker et al. used microcrystal electron diffraction (MicroED) to determine the structure of a model DNA crystal to 1.1 Å. This study shows the applicability of MicroED to nucleic acid crystallography. [ABSTRACT FROM AUTHOR]

In very thin ply laminates, delamination failure initiation occurs at much higher stress levels as compared to conventional ply laminates. This results in significant plastic deformation in the matrix accompanied by large fiber rotations. A closer look reveals that microstructure of fiber reinforced composites at large strains do not rotate with the plastic spin induced by the total deformation gradient and therefore inelasticity of such materials requires dedicated constitutive models. This paper focuses on inelastic response of such composites by using a recently proposed crystal plasticity based modeling framework and extents it by a non-local continuum damage mechanics formulation. As opposed to existing works related to composites, adapted crystal plasticity model is formulated and implemented in an implicit manner. To address the initiation and evolution of damage observed at large strains, localizing implicit gradient damage (LIGD) framework is used to degrade the slip resistance and hardening mechanisms on longitudinal and transverse slip systems by means of two separate damage variables. A user element (UEL) subroutine encapsulating all the components of the model is developed and integrated within the commercial finite element solver Abaqus. Capabilities of the model are assessed at material point, ply, and component levels by comparisons with analytical solutions and selected experimental results from the literature. • A damage extended crystal plasticity like model for thin ply laminates. • Mesh independent damage treatment with localizing implicit gradient formulation. • Different damage variables pertaining to longitudinal and transverse slip system. • Implementation of a three-field user element within Abaqus at finite strains. [ABSTRACT FROM AUTHOR]

Dislocations strongly affect the quality of Czochralski-grown germanium crystals used for various applications, however, the influence of different growth parameters on the dislocation distribution has not been extensively studied in the literature. In the present work, a simplified parametric crystal growth model is introduced which is suitable for large-scale numerical studies. The time-dependent temperature and dislocation density distributions in the crystal are calculated and analyzed. The Alexander–Haasen model is applied for dislocation modeling. Model parameters are taken from previously published discrete dislocation dynamics simulations, establishing a novel coupling between mesoscopic and macroscopic simulations. A W-shaped radial distribution of the dislocation density is obtained in the simulations. It is shown that the effective ambient temperature and crystallization front deflection have the strongest influence on the dislocation distribution. The results are compared to the experiment, showing a qualitative agreement, but also several deviations. Limitations of the considered dislocation modeling approach and the simplified thermal model are discussed. [Display omitted] • A simplified parametric model is introduced for Czochralski crystal growth. • Large-scale numerical parametric studies are carried out. • Influence of growth parameters on the dislocation distribution is analyzed. • Detailed comparison with measured dislocation density maps is performed. [ABSTRACT FROM AUTHOR]

The challenges of classic rate-independent crystal plasticity models regarding the determination of active slip systems and computation of solutions due to linear dependent slip systems are still a field of active research. In that regard, interior-point methods are promising approaches because a logarithmic barrier term naturally avoids the combinatorial active set search, and these methods are applicable even when the gradient of inequality constraints is linearly dependent. In this paper, a new interior-point algorithm suitable for rate-independent crystal plasticity at finite strains is developed. For that purpose, the postulate of maximum dissipation is recast as a constrained optimization problem whose optimality conditions are derived by utilizing interior-point approaches. This optimization problem is discretized in time by means of an exponential time integration of the flow rule, and the time-discrete equations are solved by a Newton scheme. The focus of this paper is the efficiency and robustness of the implementation of this approach. In particular, the effect of different line search procedures, favorable residual forms, preconditioning methods, barrier parameter updates and the consistent algorithmic tangent modulus are discussed and further elaborated. In addition, aspects regarding uniqueness and well-posedness of the algorithm are analyzed in a geometrically linearized setting. Efficiency and robustness of the developed algorithm are shown by numerical examples of an FCC crystal including finite element simulations without stabilizing hardening or rate-dependent effects. Furthermore, the results are compared to the well-established augmented Lagrangian formulation. [ABSTRACT FROM AUTHOR]

The generally greater degree of thermal motion of guest molecule(s) relative to the host often impedes their accurate modelling in crystal structures. We propose a 'rule-of-thumb' for estimating the maximum number of guest molecules that can be accommodated in a given amount of accessible space in an adequately modelled host structure. A survey of the Cambridge Structural Database was carried out to evaluate the fractional occupancy of the accessible space for almost 40 000 solvates involving 20 common solvents. Using widely accessible software tools, the volume of a guest is estimated as its van der Waals surface, while the guest-occupiable space of a potentially porous host is determined as that available to a virtual spherical probe. We propose terminology more appropriate to the supramolecular interpretation of surface typology: the probe-traversable and probe-accessible boundaries as traced out by the locus and surface of a spherical probe, respectively. High-throughput analysis using commercial and free software packages yielded a mean = 51.1(4)%, ranging from 45.3(6)% for hexane to 60(1)% for acetic acid. [ABSTRACT FROM AUTHOR]