Article
Chemistry, Physical
Chun Kei Lam, Bert L. de Groot
Summary: We use molecular dynamics simulations and Markov state models to investigate the dynamical details of ion permeation in potassium channels. Our results reveal that the direct knock-on permeation is the dominant mechanism across various conditions, and it is also observed in other potassium channels with conserved selectivity filters. Furthermore, we explore the dependence of permeation cycles on charge strength. These findings provide valuable insights into the conduction mechanisms in potassium channels.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Multidisciplinary Sciences
N. Gao, Z. W. Yao, G. H. Lu, H. Q. Deng, F. Gao
Summary: The study found a new diffusion mechanism for <100> interstitial dislocation loops in BCC iron using self-adaptive accelerated molecular dynamics, which represents a significant step towards understanding the mechanical behavior and microstructure evolution of the material.
NATURE COMMUNICATIONS
(2021)
Article
Polymer Science
Ting Ge, Jiuling Wang, Mark O. Robbins
Summary: As the degree of coarse-graining increases, the stress level during strain hardening decreases, but the stress-strain curves can be collapsed with a simple rescaling factor. In the same strain range, the conformational changes in local chain segments are almost the same.
Article
Chemistry, Multidisciplinary
Robert M. Ziolek, Alejandro Santana-Bonilla, Raquel Lopez-Rios de Castro, Reimer Kuhn, Mark Green, Christian D. Lorenz
Summary: In this study, the nanoscale structure of the polymer F8BT and its impact on its optical properties were investigated using molecular dynamics simulations. The researchers found a giant percolating cluster in amorphous F8BT, which has implications for the quantum yield and color shift observed in conjugated polymer-based devices and nanostructures. Additionally, the study showed that distinct conformations can be unraveled from the disordered structure of amorphous F8BT using a machine learning protocol.
Article
Polymer Science
Yasmin Khairy, Fernando Alvarez, Arantxa Arbe, Juan Colmenero
Summary: In this study, fully atomistic molecular dynamics simulations were conducted on polyisobutylene above the glass transition to characterize the dynamics of different kinds of atoms. All atoms, including main-chain carbons, demonstrated a crossover from Gaussian to non-Gaussian behavior in the intermediate scattering function. The research indicates that methyl-group rotations are coupled with the main-chain dynamics, challenging the assumption of the statistically independence of rotational and segmental motions.
Article
Engineering, Chemical
Andreas Schoenhals, Paulina Szymoniak, Mohamed A. Kolmangadi, Martin Boehning, Michaela Zamponi, Bernhard Frick, Markus Appel, Gerrit Guenther, Margarita Russina, Dmitry A. Alentiev, Maxim Bermeshev, Reiner Zorn
Summary: The study found that poly(tricyclononenes) with Si-substituted bulky side groups have high microporosity, making them potential candidates for active separation layers for gas separation membranes. The low temperature relaxation process involving methyl group rotation suggests that some methyl groups may be immobilized in their rotation due to steric hindrance.
JOURNAL OF MEMBRANE SCIENCE
(2022)
Review
Nanoscience & Nanotechnology
Vincent M. Torres, Erik Furton, Jensen N. Sevening, Elisabeth C. Lloyd, Masafumi Fukuto, Ruipeng Li, Darren C. Pagan, Allison M. Beese, Bryan D. Vogt, Robert J. Hickey
Summary: The tunable properties of thermoplastic elastomers (TPEs) allow them to be used in a wide range of applications. The design and synthesis of new macromolecules are necessary to control the mechanical properties of TPEs. In this study, in situ small-angle X-ray scattering (SAXS) measurements reveal distinct deformation mechanisms between linear and grafted TPEs, leading to enhanced mechanical properties.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Polymer Science
Dominic Wadkin-Snaith, Paul Mulheran, Karen Johnston
Summary: This study used molecular dynamics simulations to investigate the nucleation and crystallization of polymers under homogeneous and heterogeneous conditions. The presence of a surface was found to affect the crystallization behavior of the polymers. Polymers with stiff chains crystallized more readily than flexible polymers in the absence of a surface, while the presence of an isotropic surface promoted crystallization in flexible systems. The model provides insight into the mechanisms of polymer crystallization and can help in the design of nucleants for controlling polymer crystallization.
Article
Mechanics
Wuyang Zhao, Maximilian Ries, Paul Steinmann, Sebastian Pfaller
Summary: This study presents a phenomenological viscoelastic-viscoplastic constitutive model based on CG MD simulations, focusing on the intermolecular interaction of polymer chains. The model, with 10 material parameters, fits well the CG MD simulations of PS under different strain rates.
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
(2021)
Article
Biochemistry & Molecular Biology
Cheng-Dong Li, Muhammad Junaid, Xiaoqi Shan, Yanjing Wang, Xiangeng Wang, Abbas Khan, Dong-Qing Wei
Summary: Cholesterol affects the dimerization of C99 but does not directly compete with it. The presence of cholesterol stabilizes the C99 dimer and influences the production of Aβ.
FRONTIERS IN MOLECULAR BIOSCIENCES
(2022)
Article
Engineering, Multidisciplinary
Huesnue Dal, Osman Gueltekin, Selcuk Basdemir, Alp Kagan Acan
Summary: The optimal use and design of amorphous glassy polymers in goods is essential in various industrial sectors, with fracture response depending on microstructure, temperature level, and loading rate. Shear yielding and crazing are described in terms of their evolution equations, and fracture is modeled using a crack phase-field approach, considering both ductile and brittle failure simultaneously. This novel failure criterion models macroscopic crack initiation and growth leading to ductile or brittle fracture, demonstrating predictive performance through fitting of experimental data.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2022)
Article
Chemistry, Multidisciplinary
Jincheng Ji, Weihua Zhu
Summary: The effects of vacancy defects on the structure, stability, and initial decomposition mechanisms of BTF were studied. The vacancies were found to be distributed in the form of aggregation thermodynamically. Introduction of vacancies did not change the initial decomposition path of BTF, with N-O bond fracture being the most important decomposition pathway. Additionally, BTF molecules around vacancy defects showed enhanced decomposition.
Article
Chemistry, Multidisciplinary
Carlos A. Ramos-Guzman, Milorad Andjelkovic, Kirill Zinovjev, J. Javier Ruiz-Pernia, Inaki Tunon
Summary: In this study, the by-residue decomposition of noncovalent interactions and analysis of naturally occurring mutations were used to detect potential mutations in the 3CL protease of SARS-CoV-2 that confer resistance to nirmatrelvir. It was found that the E166V mutation reduces the binding affinity of the protease to nirmatrelvir and increases the activation free energy for the formation of the covalent enzyme-inhibitor complex, resulting in resistance to the treatment with this drug. The conclusions of this study can be useful for predicting the consequences of introducing nirmatrelvir in the virus fitness landscape and designing new inhibitors targeting possible resistance mechanisms.
Article
Engineering, Mechanical
Chuanlong Xu, Xiaobao Tian, Wentao Jiang, Qingyuan Wang, Haidong Fan
Summary: This study investigates the migration mechanisms of symmetric tilt grain boundaries (STGBs) in magnesium using molecular dynamic simulations. The results show that the migration mechanisms of grain boundaries are significantly influenced by their structure, with small angle STGBs migrating through twin nucleation and growth, large angle STGBs migrating through the glide of grain boundary dislocations, and medium angle STGBs transforming into twin boundaries through the emission of lattice dislocations/stacking faults.
INTERNATIONAL JOURNAL OF PLASTICITY
(2022)
Article
Multidisciplinary Sciences
Weiwei He, Yen-Lin Chen, Lois Pollack, Serdal Kirmizialtin
Summary: The structural diversity of double-stranded DNA and RNA helices, with some variations linked to sequence serving as signaling units for protein-binding partners, is of fundamental importance in understanding their mechanisms. By integrating solution x-ray scattering and molecular dynamics simulations, robust correlations between features in the profiles and duplex geometry have been identified, providing atomic-level insights into their structural diversity. Notably, dsRNA shows sensitivity to the valence and identity of associated cations.
Article
Automation & Control Systems
Haoyu Li, Xin Wang, Junjie Zhang, Binyu Wang, Marina Breisch, Alexander Hartmaier, Igor Rostotskyi, Vyacheslav Voznyy, Yu Liu
Summary: While pure titanium is already a popular choice for medical applications due to its mechanical and chemical properties, this study explores how surface texturing can further enhance its functionalities. The researchers used picosecond pulsed laser ablation to create precise mesh-type surface textures on pure titanium, resulting in improved wettability and biocompatibility. Evaluation tests showed that the mesh-type surface textures had a positive effect on the biocompatibility of BMSC cells due to enhanced hydrophilicity.
INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY
(2022)
Article
Materials Science, Multidisciplinary
Abhishek Biswas, Surya R. Kalidindi, Alexander Hartmaier
Summary: This study presents a hybrid method that combines the classical crystallographic yield locus method (CYL) with the crystal plasticity finite element method (CPFEM) to determine the anisotropic yield locus (YL) of a material. The hybrid method is shown to produce reliable results for diverse crystallographic textures, even with pronounced plastic anisotropy. The calibrated CYL method is used to construct a smooth yield function that can potentially be used in standard continuum plasticity methods for finite element analysis.
MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING
(2022)
Article
Materials Science, Coatings & Films
Navneet K. Singh, Gidla Vinay, Andrew S. M. Ang, Dhiraj K. Mahajan, Harpreet Singh
Summary: This study assesses the synergic effect of cavitation erosion and corrosion on two HVOF-sprayed nickel-based cermet coatings, WC-NiCr and WC-H, on Monel K-500 substrate. It was found that WC-NiCr coating reduced the cavitation erosion losses in Monel alloy by 45% and had better corrosion results. SEM analysis revealed that the corrosive medium generated defects on the coating surface, increasing the cavitation erosion losses. WC-NiCr coating is recommended to enhance the cavitation-corrosion resistance in Monel K-500 alloy.
SURFACE & COATINGS TECHNOLOGY
(2022)
Article
Engineering, Mechanical
Vishal Singh, Rakesh Kumar, Yann Charles, Dhiraj K. Mahajan
Summary: Modeling the coupled diffusion-mechanics response is essential for understanding the multifaceted hydrogen-assisted damage evolution in metallic materials. This study utilizes a dislocation density-based crystal plasticity model coupled with a hydrogen diffusion/trapping model to simulate the deformation and failure under the HELP mechanism of hydrogen embrittlement. The findings highlight the significant role of hydrogen in influencing dislocation interactions and density, leading to macroscopic softening or hardening.
INTERNATIONAL JOURNAL OF PLASTICITY
(2022)
Article
Materials Science, Multidisciplinary
Tushita Rohilla, Narinder Singh, Narayanan C. Krishnan, Dhiraj K. Mahajan
Summary: Fuel cells are efficient energy conversion devices with various applications. The proton conductivity of Polymer Electrolyte Membrane (PEM) is crucial for fuel cell performance. Developing alternatives to commercial PEMs based on costly perfluorinated ionomers is a pressing need. Sulfonated polyimides (SPIs) have shown better proton conductivity than commercial PEMs at lower hydration levels and higher temperatures, but finding alternative SPI PEMs requires extensive experimental efforts. Machine learning approaches can reduce these efforts and predict proton conductivity.
COMPUTATIONAL MATERIALS SCIENCE
(2023)
Article
Chemistry, Physical
Rakesh Kumar, Aman Arora, Dhiraj K. Mahajan
Summary: Small-scale, low-cycle fatigue experiments were conducted on hydrogen charged nickel specimens to identify potential intergranular crack initiation sites. A crystal plasticity model considering dislocation density and a hydrogen transport model based on slip-rate were developed to study the micromechanics. A fatigue indicator parameter (FIP) was introduced to model the crack initiation process by considering plastic slip, GB stress, and local hydrogen concentration. The analysis showed that special GBs retain more hydrogen due to low diffusivity, while random GBs quickly diffuse hydrogen to the bulk.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Chemistry, Physical
Abhishek Biswas, Dzhem Kurtulan, Timothy Ngeru, Abril Azocar Guzman, Stefanie Hanke, Alexander Hartmaier
Summary: This study focuses on investigating the mechanical behavior of low-nickel austenitic steel under high-pressure torsion fatigue (HPTF) loading, particularly the axial creep deformation observed in the experiment. The results show that a J2 plasticity model with an associated flow rule fails to describe the axial creep behavior, while a micromechanical model based on an empirical crystal plasticity law with kinematic hardening described by the Ohno-Wang rule can accurately match the HPTF experiments. Therefore, our findings confirm the versatility of crystal plasticity combined with microstructural models in describing the mechanical behavior of materials under reversing multiaxial loading situations.
Article
Materials Science, Multidisciplinary
Mahdieh Shahmardani, Ruslan Logvinov, Tomas Babinsky, Stefan Guth, Shubhadip Paul, Abhishek Biswas, Napat Vajragupta, Alexander Hartmaier
Summary: This work investigates the cyclic deformation behavior of additively manufactured 316L austenitic stainless steel. Specimens of 316L steel are produced using powder bed fusion of metals with laser beams (PBF-LB/M) with different parameters, and cyclic strain tests are conducted to assess their deformation behavior under cyclic loads at room temperature. Additionally, a micromechanical model based on representative volume elements (RVE) is developed to simulate the deformation-dependent internal stresses within the microstructure. The study reveals significant effects of specimen orientation and crystallographic texture on cyclic behavior, with a minor influence of grain shape.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Engineering, Mechanical
Aman Arora, Aanchna Sharma, Mohit Singh, Dhiraj K. Mahajan, Vinod Kushvaha
Summary: This study presents an extensive experiment on the fatigue response of glass-filled epoxy composites under cyclic loading. Rod-shaped particulate glass fibers with volume fractions of 0%, 5%, 10%, and 15% are used to reinforce the epoxy matrix. The mechanical behavior of the resulting composite is examined under monotonic tensile loading and tension-tension cyclic fatigue loading. The study utilizes in-situ low cycle fatigue testing to investigate the damage mechanisms leading to crack initiation and propagation.
INTERNATIONAL JOURNAL OF FATIGUE
(2023)
Article
Materials Science, Multidisciplinary
Rakesh Kumar, Dhiraj K. Mahajan
Summary: In this study, a coupled framework of dislocation density-based crystal plasticity model and slip-rate based hydrogen transport model is developed to simulate hydrogen-assisted damage at the deforming crack-tip. The evolving hydrogen concentration is accounted for by chemical potential-based boundary conditions and mobile dislocation-assisted hydrogen transport. A novel fracture indicator parameter is proposed to quantify the damage, considering the combined effect of local hydrogen concentration, accumulated plastic slip, and stress triaxiality. Depending on the crystal orientation, the damage is shown to be associated either with an individual hydrogen embrittlement mechanism (hydrogen-enhanced localized plasticity and hydrogen-enhanced decohesion) or their synergistic effect at the crack tip.
MECHANICS OF MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
G. Tolooei Eshlaghi, G. Egels, S. Benito, M. Stricker, S. Weber, A. Hartmaier
Summary: This article presents a robust and comprehensive approach for reconstructing the three-dimensional microstructure of two-phase materials based on electron backscatter diffraction (EBSD) maps from orthogonal surfaces. The method involves processing surface maps using spatial correlation functions combined with principal component analysis (PCA) to generate a representative fingerprint. The approach is demonstrated to accurately describe the microstructure of a metastable austenitic steel and can generate statistically equivalent microstructures.
FRONTIERS IN MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Santiago Benito, Gero Egels, Alexander Hartmaier, Sebastian Weber
Summary: The microstructure plays a crucial role in connecting the thermodynamic, compositional, and kinetic stochasticity with macroscopic behavior. In this study, we propose a fast first-order variogram as a statistical tool to comprehensively describe chemical segregations in metallic materials. We discuss its derivation, application, advantages, and limits, and compare it with popular texture characterization techniques. This method provides a simple yet powerful way to characterize the severity of micro and mesosegregations and quantify their influence on material behavior.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Materials Science, Multidisciplinary
Jan Schmidt, Alexander Hartmaier
Summary: This article proposes a new generic descriptor for crystallographic texture that allows an explicit consideration of the microstructure in data-driven constitutive modeling. It provides a pathway to microstructure-sensitive data-driven constitutive modeling.
JOURNAL OF MATERIALS SCIENCE
(2023)
Article
Nanoscience & Nanotechnology
Aravindh Nammalvar Raja Rajan, Marcel Krochmal, Mahdieh Shahmardani, Thomas Wegener, Alexander Hartmaier, Thomas Niendorf, Ghazal Moeini
Summary: The AM process continues to attract attention in industrial and academic research due to its high degrees of design freedom and flexibility in the production process. However, the use of AM-processed components for parts under cyclic loading is limited by significant variance in cyclic behavior and the effects of AM-associated defects. This study examines and predicts the low-cycle fatigue behavior of AlSi10Mg parts produced by laser-based powder bed fusion in both the as-built and direct-aged condition using experiments and microstructure-sensitive models. The applied modeling framework accurately predicts the LCF behavior of AlSi10Mg under various strain amplitudes and ratios for both conditions.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Materials Science, Multidisciplinary
Aman Arora, Harpreet Singh, Ilaksh Adlakha, Dhiraj K. Mahajan
Summary: This study provides new insights into the role of vacancy-hydrogen (VaH) complexes in the hydrogen embrittlement of nickel. Atomistic simulations are used to investigate the effect of hydrogen concentration and crystal orientations on dislocation behavior in nickel. The study finds that VaH complexes lead to higher embrittlement compared to hydrogen atoms alone. Additionally, the presence of VaH complexes causes softening during dislocation emission and hardening during dislocation propagation, which is consistent with experimental observations of dislocation structures on fractured surfaces in the presence of hydrogen.
MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING
(2023)
