Molecular Dynamics Simulation of Thermomechanical Properties of Montmorillonite Crystal. 1. Isolated Clay Nanoplate

Abstract

The structure and mechanical properties of clay nanoparticles is a subject of growing interest because of their numerous applications in engineering. We present the results of molecular dynamics simulation for a single nanoplate of pyrophyllite - a 2:1 clay mineral consisting of two tetrahedral sheets of SiO4 and an intervening octahedral AlO6 sheet. Simulations were performed in the temperature interval from 5 to 750 K using the ionic-type potentials of Cygan et al. On this basis the temperature dependences of structural parameters, characterizing both tetrahedral and octahedral sheets as well as single lamella, have been studied. Two slightly different structures were observed in this wide temperature interval. The mechanical properties of the nanoplate were calculated from stress-strain diagrams, which have been obtained at relatively slow rates of deformation (for molecular simulations). Using different types of loading, we calculated the full elasticity tensor and estimated the influence of temperature on its components. We estimated also the bending and torsion stiffnesses of the nanoplate as specific characteristics of this type of particle. Because the nanoplate is atomically thin, a reasonable determination of the thickness is a nontrivial problem, both in the modeling of mechanical properties and in physical interpretation of the obtained data. We propose a procedure for its calculation.

Study of the dynamics of poly(ethylene oxide) by combining molecular dynamic simulations and neutron scattering experiments

“…In fact, PEO has also been a focus of interest for studying confinement effects under different conditions, such as e.g., in nanocomposites. 25,26 Obviously, the proper characterization of the deviations from the bulk behavior of PEO under different confinement situations demands the detailed knowledge of the structural and dynamical properties of the neat polymer at a molecular scale. This can be provided by the combination of neutron scattering experiments and molecular dynamics ͑MD͒ simulations.…”

“…7,[27][28][29][30][31][32][33][34][35][36][37][38][39] Regarding MD simulations on PEO, a relatively large number of publications can be found in literature. 25,26,[40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]60 Some of them deal mainly with structural properties, 48,50,51,[53][54][55][56]60 but the local dynamics is also addressed in others; 42,52,57 sometimes the works have been motivated by its use as polyelectrolyte 40,41,49 or have been focused on its confined behavior. …”

“…25,26,[40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]60 Some of them deal mainly with structural properties, 48,50,51,[53][54][55][56]60 but the local dynamics is also addressed in others; 42,52,57 sometimes the works have been motivated by its use as polyelectrolyte 40,41,49 or have been focused on its confined behavior. 25,26,42 Always fully atomistic models have been investigated, except in the case of Refs. 49 and 55 where united atom simulations were performed.…”

Computer simulation study of the materials properties of intercalated and exfoliated poly(ethylene)glycol clay nanocomposites

“…For instance, the high surface area and the small interparticle distances of the platelets can, in principle, significantly alter the properties of the polymer matrix, such as the polymer crystalline morphology, chain conformation and dynamics through confinement effects in a nanoscopic environment. [17][18][19][20] Thus, many factors could potentially be responsible for the enhancement offered by these nanofillers. In order to gain greater control over the material properties and hence the design of future materials, a better understanding of the relative contribution from each source is needed.…”

Hybrid and Hierarchical Composite Materials

“…The effect of temperature on the stiffness coefficients of nanoclay have been studied using molecular dynamic simulation (Mazo et al 2008). A parallelepiped containing 45 unit cells (1800 atoms) was constructed and periodic boundary condi- tions were applied on all three directions.…”