scholarly journals Molecular Dynamics Simulation in the Interlayer of Mixed-Layer Clays Due to Hydration and Swelling Mechanism

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 586
Author(s):  
Yu Yang ◽  
Sanjeev Adhikari ◽  
Guoyuan Xu
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonds ◽  
Interaction Energy ◽  
Mixed Layer ◽  
Bound Water ◽  
Swelling Behavior ◽  
Dynamics Simulation ◽  
Basal Spacing ◽  
Water Interaction ◽  
Swelling Mechanism

The swelling behavior of clay minerals is widely known for its importance in soil and environmental sciences and its detrimental effects in engineering fields. Although more than 70 percent of all clays are of mixed-layer types, the vast majority of the previous experiments and simulations are focused on pure clays, which cause the swelling mechanism of the widespread mixed-layer clay (MLC) and its role in soils are little understood, especially the most common illite-montmorillonite (I-M) mixed-layer clay (MLC). This paper reports on a molecular dynamics (MD) study of the differences in swelling behavior between I-M MLCs containing K+ and Na+ and Na-montmorillonite (MMT). It captures the evolution of quantitative properties such as basal spacing d, interaction energy, and many hydrogen bonds in the clay interlayer, increasing hydration for the first time through the scripts. It is found that MLCs have smaller swellings than Na-MMT due to the asymmetric interlayer charges and mixed counterions in the I-M interlayer. However, in terms of the interaction energy for the in-depth reason of swelling, it is found that the clay-clay interaction energy and the clay-ion interaction energy drop, while the clay-water interaction energy increases with increasing hydration. In addition, the attractive interaction of clay-bound water seriously promotes swelling, and it is mainly composed of Coulomb interaction and Van der Waals interaction. The higher the K+ concentration, the more noticeable these phenomena are. Besides, it is also reported that the number and distribution mechanism of hydrogen bonds in MLCs are very different from that of pure clay. This work provides insight into the molecular mechanism for initial swelling and clay-bound water interaction in widespread MLCs. This will help to decipher its specific role in soils and minimize clay swelling.

Molecular dynamics simulation insight into the temperature dependence and healing mechanism of an intrinsic self-healing polyurethane elastomer

2020 ◽  
Vol 22 (31) ◽  
pp. 17620-17631
Author(s):  
Xianling Chen ◽  
Jing Zhu ◽  
Yanlong Luo ◽  
Jun Chen ◽  
Xiaofeng Ma ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Hydrogen Bonds ◽  
Molecular Diffusion ◽  
Healing Process ◽  
The Self ◽  
Dynamics Simulation ◽  
Polyurethane Elastomer ◽  
Self Healing ◽  
Insight Into

The changes in the type and number of hydrogen bonds as well as the microscopic behavior of molecular diffusion in the self-healing process of polyurethane are revealed.

scholarly journals Molecular Dynamics Simulation of Nanoscale Elastic Properties of Hydrated Na-, Cs-, and Ca-Montmorillonite

2022 ◽  
Vol 12 (2) ◽  
pp. 678
Author(s):  
Lianfei Kuang ◽  
Qiyin Zhu ◽  
Xiangyu Shang ◽  
Xiaodong Zhao
Keyword(s):  
Molecular Dynamics ◽  
Water Content ◽  
Elastic Properties ◽  
Bonding Strength ◽  
Stable State ◽  
Dynamics Simulation ◽  
Basal Spacing ◽  
Stiffness Tensor ◽  
Interlayer Water ◽  
Out Of Plane

The knowledge of nanoscale mechanical properties of montmorillonite (MMT) with various compensation cations upon hydration is essential for many environmental engineering-related applications. This paper uses a Molecular Dynamics (MD) method to simulate nanoscale elastic properties of hydrated Na-, Cs-, and Ca-MMT with unconstrained system atoms. The variation of basal spacing of MMT shows step characteristics in the initial crystalline swelling stage followed by an approximately linear change in the subsequent osmotic swelling stage as the increasing of interlayer water content. The water content of MMT in the thermodynamic stable-state conditions during hydration is determined by comparing the immersion energy and hydration energy. Under this stable hydration state, the nanoscale elastic properties are further simulated by the constant strain method. Since the non-bonding strength between MMT lamellae is much lower than the boning strength within the mineral structure, the in-plane and out-of-plane strength of MMT has strong anisotropy. Simulated results including the stiffness tensor and linear elastic constants based on the assumption of orthotropic symmetry are all in good agreement with results from the literature. Furthermore, the out-of-plane stiffness tensor components of C33, C44, and C55 all fluctuate with the increase of interlayer water content, which is related to the formation of interlayer H-bonds and atom-free volume ratio. The in-plane stiffness tensor components C11, C22, and C12 decrease nonlinearly with the increase of water content, and these components are mainly controlled by the bonding strength of mineral atoms and the geometry of the hydrated MMT system. Young’s modulus in all three directions exhibits a nonlinear decrease with increasing water content.

scholarly journals Solvent Effects on Catechol Crystal Habits and Aspect Ratios: A Combination of Experiments and Molecular Dynamics Simulation Study

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 316 ◽  
Author(s):  
Dan Zhu ◽  
Shihao Zhang ◽  
Pingping Cui ◽  
Chang Wang ◽  
Jiayu Dai ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Hydrogen Bonds ◽  
Solvent Effects ◽  
Dynamics Simulation ◽  
Crystal Habit ◽  
Aspect Ratios ◽  
Solvent Environment ◽  
Solvent Adsorption ◽  
Attachment Energy

This work could help to better understand the solvent effects on crystal habits and aspect ratio changes at the molecular level, which provide some guidance for solvent selection in industrial crystallization processes. With the catechol crystal habits acquired using both experimental and simulation methods in isopropanol, methyl acetate and ethyl acetate, solvent effects on crystal morphology were explored based on the modified attachment energy model. Firstly, morphologically dominant crystal faces were obtained with the predicted crystal habit in vacuum. Then, modified attachment energies were calculated by the molecular dynamics simulation to modify the crystal shapes in a real solvent environment, and the simulation results were in agreement with the experimental ones. Meanwhile, the surface properties such as roughness and the diffusion coefficient were introduced to analyze the solvent adsorption behaviors and the radial distribution function curves were generated to distinguish diverse types of interactions like hydrogen bonds and van der Waals forces. Results show that the catechol crystal habits were affected by the combination of the attachment energy, surface structures and molecular interaction types. Moreover, the changing aspect ratios of catechol crystals are closely related to the existence of hydrogen bonds which contribute to growth inhibition on specific faces.

The influence of a type III antifreeze protein and its mutants on methane hydrate adsorption–inhibition: a molecular dynamics simulation study

2019 ◽  
Vol 21 (39) ◽  
pp. 21836-21846 ◽  
Author(s):  
Mitra Maddah ◽  
Mina Maddah ◽  
Kiana Peyvandi
Keyword(s):  
Molecular Dynamics ◽  
Amino Acids ◽  
Molecular Dynamics Simulation ◽  
Hydrogen Bonds ◽  
Simulation Study ◽  
Methane Hydrate ◽  
Hydrophobic Interactions ◽  
Dynamics Simulation ◽  
Antifreeze Activity ◽  
Adsorption Inhibition

Antifreeze proteins inhibit hydrate growth by hydrophobic interactions in cooperation with hydrogen bonds. Mutation of three polar amino acids (Asn14, Thr18, and Gln44) elucidates the molecular mechanism of AFP III antifreeze activity.

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