Reactive Molecular Dynamics Simulations to Understand Mechanical Response of Thaumasite under Temperature and Strain Rate Effects

Hajilar, Shahin; Shafei, Behrouz; Cheng, Tao; Jaramillo-Botero, Andrés

doi:10.1021/acs.jpca.7b02824

Cited by 10 publications

(4 citation statements)

References 37 publications

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“…For Si-O, they are 4.06, 4.12 (2 × 1 × 2), and 4.23 for the 1 × 1 × 2, 2 × 1 × 2, and 2 × 2 × 2 systems, respectively, clearly indicating an increase of the Si-O coordination number for larger unit cells, due to the presence of these highly-coordinated motifs. It is worth mentioning that Si atoms with coordination numbers larger than 4 have been reported in a couple of synthesized minerals; namely, a high-pressure phase of MgSi(OH) 6 [126] and a dense phase (so-called phase D) of MgSi(OH) 2 O 4 [127,128], predicted by means of theoretical calculations to occur in thaumasite [129], a naturally-occurring mineral present in the Earth's crust. For Mg-O, the coordination numbers are kept at 5.82 for all unit cell systems, probably due to compensation effects in the different Mg coordination spheres.…”

Section: Unit Cell Size Effects In the Amorphisation Of The Mg 2 Sio mentioning

confidence: 99%

Multiscale Computational Simulation of Amorphous Silicates’ Structural, Dielectric, and Vibrational Spectroscopic Properties

2018

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Silicates are among the most abundant and important inorganic materials, not only in the Earth’s crust, but also in the interstellar medium in the form of micro/nanoparticles or embedded in the matrices of comets, meteorites, and other asteroidal bodies. Although the crystalline phases of silicates are indeed present in nature, amorphous forms are also highly abundant. Here, we report a theoretical investigation of the structural, dielectric, and vibrational properties of the amorphous bulk for forsterite (Mg2SiO4) as a silicate test case by a combined approach of classical molecular dynamics (MD) simulations for structure evolution and periodic quantum mechanical Density Functional Theory (DFT) calculations for electronic structure analysis. Using classical MD based on an empirical partial charge rigid ionic model within a melt-quenching scheme at different temperatures performed with the GULP 4.0 code, amorphous bulk structures for Mg2SiO4 were generated using the crystalline phase as the initial guess. This has been done for bulk structures with three different unit cell sizes, adopting a super-cell approach; that is, 1 × 1 × 2, 2 × 1 × 2, and 2 × 2 × 2. The radial distribution functions indicated a good degree of amorphization of the structures. Periodic B3LYP-geometry optimizations performed with the CRYSTAL14 code on the generated amorphous systems were used to analyze their structure; to calculate their high-frequency dielectric constants (ε∞); and to simulate their IR, Raman, and reflectance spectra, which were compared with the experimental and theoretical crystalline Mg2SiO4. The most significant changes of the physicochemical properties of the amorphous systems compared to the crystalline ones are presented and discussed (e.g., larger deviations in the bond distances and angles, broadening of the IR bands, etc.), which are consistent with their disordered nature. It is also shown that by increasing the unit cell size, the bulk structures present a larger degree of amorphization.

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Section: Unit Cell Size Effects In the Amorphisation Of The Mg 2 Sio mentioning

confidence: 99%

Multiscale Computational Simulation of Amorphous Silicates’ Structural, Dielectric, and Vibrational Spectroscopic Properties

2018

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“…Furthermore, molecular dynamics (MD) simulation has predicted that the stress‐strain relationships of thaumasite are substantially dependent on the direction of the applied strain. This study also revealed that the mechanical strength of thaumasite differed depending on the orthogonal directions …”

Section: Introductionmentioning

confidence: 59%

“…This study also revealed that the mechanical strength of thaumasite differed depending on the orthogonal directions. 14 The application of cementitious materials under severe conditions requires complete understanding of the mineral characteristics of constituent crystals. Although the temperature-related stability and elastic properties of thaumasite near ambient conditions have been studied, no article has reported the structural changes of thaumasite under high pressure.…”

Section: Introductionmentioning

confidence: 99%

Pressure‐induced anomalous behavior of thaumasite crystal

Moon

Bae

et al. 2020

J Am Ceram Soc

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This work investigated the structural responses of thaumasite crystal, an important phase to understand the structural integrity of concrete‐based structures, using synchrotron‐based X‐ray diffraction and first‐principles calculations. The 100 peak was immediately diffused upon the contact of pressure‐transmitting medium, but regenerated under subsequent pressurization. Under high pressure, it showed complex nonlinear responses; lattice parameters a and b became stiffer first (between 1.06 and 2.32 GPa) then lattice parameter c became significantly incompressible (beyond 2.32 GPa). The densification of hydrogen bond network in the channels surrounded by calcium silicate columns and the interaction between the network and the medium caused the first nonlinear response and completely weakened the periodicity of lattice parameters a and b (beyond 5.37 GPa). However, this amorphization phenomenon did not leave a permanent damage on the crystal, leading to the reshaping of the weakened crystallinity upon the release of pressure. Simulation results further elucidated the compressive mechanism of thaumasite crystal. It confirmed that deformation due to pressure mainly took place in the channel space, thus strengthening the hydrogen bonds. It also suggested a potential symmetry breaking of hexagonal structure that makes the stiffness characteristics of the crystal highly anisotropic under pressure.

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“…A periodic boundary condition is applied to the three spatial directions of each simulation box. − The Polak–Ribiere version of the conjugate gradient algorithm is used to minimize the potential energy of the atomistic models. The energy-minimized models are then equilibrated using the MD method in an isothermal–isobaric ensemble (NPT) at 450 K and 0 bar for 1.0 ns (nanosecond, 10 –9 s).…”

Section: Computational Detailsmentioning

confidence: 99%

Multiscale Investigation of Interfacial Thermal Properties of n-Octadecane Enhanced with Multilayer Graphene

Hajilar¹,

Shafei²

2019

J. Phys. Chem. C

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Among various phase change materials that can be employed for energy-storage purposes, octadecane has received growing attention due to its chemical stability paired with nontoxic/noncorrosive characteristics. Octadecane, however, has a low thermal conductivity, which prevents it from efficient heat exchange with the surrounding environment. To address this issue, the promise of adding carbon-based nanofillers, including single and multilayer graphene (MLG), is investigated in this study from a fundamental perspective. For this purpose, the reverse nonequilibrium molecular dynamics method is employed according to the Muller–Plathe algorithm to understand the mechanisms governing thermal conductance at the interface of the octadecane matrix and graphene fillers. Based on rigorous vibration power spectrum analyses, it is revealed that interfacial thermal resistance increases by increasing the number of graphene layers. To scale up the findings of atomistic simulations and determine the macroscale thermal conductivity of octadecane–MLG composites, the effective medium theory is employed. The influence of MLG filler’s length and volume fraction on the composite’s thermal conductivity is investigated in detail. The outcome of this study provides the insight necessary to enhance the thermal transport properties of octadecane (and other similar paraffinic materials) for efficient energy-storage systems.

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Reactive Molecular Dynamics Simulations to Understand Mechanical Response of Thaumasite under Temperature and Strain Rate Effects

Cited by 10 publications

References 37 publications

Multiscale Computational Simulation of Amorphous Silicates’ Structural, Dielectric, and Vibrational Spectroscopic Properties

Multiscale Computational Simulation of Amorphous Silicates’ Structural, Dielectric, and Vibrational Spectroscopic Properties

Pressure‐induced anomalous behavior of thaumasite crystal

Multiscale Investigation of Interfacial Thermal Properties of n-Octadecane Enhanced with Multilayer Graphene

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