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 Effects of Temperature on Structural Properties of Hydrated Montmorillonite: Experimental Study and Molecular Dynamics Simulation

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Wangbing Hong ◽  
Jie Meng ◽  
Changdong Li ◽  
Shengyi Yan ◽  
Xin He ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Water Content ◽  
Structural Properties ◽  
Environmental Changes ◽  
Electrostatic Force ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Interlayer Water ◽  
Layer Spacing ◽  
Bonding Structure

Montmorillonite (MMT) is highly sensitive to environmental changes and therefore plays a key role in the structural evolution of rocks and soils and even damage and disasters. The effects of important environmental factors (the temperature and water content) on MMT structural properties require in-depth study. The structure and morphology of sodium montmorillonite (Na-MMT) and its thermal products (micro-nanoparticles) were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). A molecular dynamics (MD) simulation was performed to investigate how temperature (below the failure temperature of the Na-MMT crystal layer) affects the structural properties of hydrated MMT. (1) The laboratory results showed that increasing the temperature significantly affected water molecules, and the particle aggregates exhibited inhomogeneous thermal expansion. The interlayer structure collapsed at 500–700°C. (2) In the simulation, the pull-off force inhibited interactions among oxides, crystal layers on both sides of the sample, and the bonding structure of water molecules, thus exposing the stress on the bonding body for analysis. The MMT ultimate stresses in the X, Y, and Z directions all trended downward with increasing water content and temperature. (3) Environmentally induced damage was most likely to occur in the Z direction. Increasing the number of interlayer water molecules increased the layer spacing and considerably weakened van der Waals forces, such that the roles of the electrostatic force and the interlayer hydrogen bond network gradually became significant. The most significant impact of increasing the temperature was reflected in the hydrogen bonding network, resulting in the destruction of the interlayer water bridge, the gradual failure of the layered bonding structure, and the formation or development of cracks. This improved understanding of the structural properties of MMT aggregates under environmental change advances research on the evolutionary behaviour of nano-, micro-, and macrostructures of rocks and soils.

Comparison of the effect of poly(N-vinyl caprolactam) and poly(N-isopropyl acrylamide) trimers on the stability of hydrated Na-montmorillonite: A molecular dynamics study

2020 ◽  
pp. 096739112093524
Author(s):  
Jiafang Xu ◽  
Moussa Camara ◽  
Hualin Liao ◽  
Hong Guo ◽  
Kouassi Louis Kra ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Conformational Changes ◽  
Stable State ◽  
Dynamics Simulation ◽  
Effect Of Temperature ◽  
Radius Of Gyration ◽  
Molecular Arrangement ◽  
Isopropyl Acrylamide ◽  
The Stability ◽  
The Impact

In the present study, we performed a molecular dynamics simulation of the intercalation of poly( N-isopropyl acrylamide) (NIPAM)3 and poly( N-vinyl caprolactam) (NVCL)3 trimers into Na-montmorillonite (Na-Mt) to evaluate their effects on the interlayer structure and the stability of hydrated Na-Mt. The impact of both trimers on the interlayer species and their dynamics properties at different temperatures in a canonical ensemble (NVT) were investigated. The results showed that the electrostatic forces exerted by Na cations on H2O molecules and the interlayer H2O molecular arrangement are not affected by the rise in temperature after adding both trimers. Trimer addition reinforced the structure of interlayer H2O molecules so that the effect of temperature increase on them became negligible. The structural dynamics evolution of the radius of gyration of both trimers showed the existence of conformation changes when temperature increased. These conformational changes are more complex in the case of (NVCL)3 than (NIPAM)3 due to its large monomers. Both trimers reduced the mobility of interlayer particles with a better inhibition effect obtained for (NVCL)3 compared to (NIPAM)3. The concentration profile of interlayers’ species showed the affinity of Na cations for clay mineral surfaces while H2O molecules moved away. Compared these two trimers, the most stable state of Na-Mt is achieved with (NVCL)3. These results could help highlight the inhibition properties of (NIPAM)3 and (NVCL)3 on hydrated Na-Mt and to predict its stability against changes in environmental conditions.

Molecular dynamics simulation of interlayer water embedded in phospholipid bilayer

2014 ◽  
Vol 36 ◽  
pp. 49-56 ◽  
Author(s):  
Won Bae Han ◽  
Suk Jun Kim ◽  
Hyeun Hwan An ◽  
Hee-Soo Kim ◽  
Yongdeok Kim ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Phospholipid Bilayer ◽  
Dynamics Simulation ◽  
Interlayer Water

A molecular dynamics simulation study of elastic properties of HMX

2003 ◽  
Vol 119 (14) ◽  
pp. 7417-7426 ◽  
Author(s):  
Thomas D. Sewell ◽  
Ralph Menikoff ◽  
Dmitry Bedrov ◽  
Grant D. Smith
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Elastic Properties ◽  
Simulation Study ◽  
Dynamics Simulation
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