Improved scaling of temperature-accelerated dynamics using localization

Shim, Yunsic; Amar, Jacques G.

doi:10.1063/1.4954996

Cited by 4 publications

(1 citation statement)

References 53 publications

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“…The simulations were performed at a relatively high temperature (e.g., 600 K) to accelerate the crossing of kinetic barriers. This approach is commonly employed in temperature-accelerated dynamics (TAD) and temperature-based replica exchange molecular dynamics (T-REMD). − In the fully dehydrated state, Rn quickly approached HKUST-1 and entered LCage-I. It was then transiently adsorbed by the triangular aperture-I of SCage from ∼3.77 to 3.78 ns before being captured by a SCage (Figure d, first).…”

Section: Resultsmentioning

confidence: 99%

Water Unexpectedly Impacts Both Thermodynamics and Kinetics of Rn Removal in HKUST-1

Geng,

Mao,

et al. 2023

J. Phys. Chem. C

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Excessive radon (Rn) exposure remains a significant risk factor for lung cancer in the general population. Metal–organic frameworks (MOFs) have emerged as promising materials for Rn radiation protection due to their unique characteristics, including large surface areas and customizable porous structures. However, the presence of water molecules, both during the synthesis process and in humid air, has often been overlooked but can significantly impact the Rn adsorption performance of MOFs in practical applications. In this study, we conducted a comprehensive investigation into the influence of varying water contents on the Rn selectivity and Rn adsorption capacity of HKUST-1, a prospective candidate. Our findings revealed that the primary Rn capture site within HKUST-1 is a tetrahedral cage (SCage) with a diameter of approximately 5.4 Å, which is ideally suited for accommodating Rn. Interestingly, increasing water content enhances the Rn adsorption capacity and selectivity of HKUST-1, primarily due to thermodynamic advantages. However, fully coordinated water molecules can give rise to additional narrow pore apertures (∼3.7 Å), resulting in a high kinetic barrier (∼16.8 kcal/mol) that hampers Rn adsorption by SCage. Consequently, water molecules play a crucial role in regulating the delicate balance between thermodynamics and kinetics in Rn adsorption by modifying the pore aperture morphology of the adsorption site within HKUST-1. Our theoretical calculations predict the optimal range of water content in HKUST-1 for efficient Rn removal, spanning from 0 wt % (fully dehydrated) to 8 wt % (fully coordinated). These findings not only provide theoretical explanations and guidance for future experimental endeavors but also offer valuable insights and references into the role of water molecules in modulating gas separation within MOFs containing open metal sites under different humidity or activation levels.

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Section: Resultsmentioning

confidence: 99%

Water Unexpectedly Impacts Both Thermodynamics and Kinetics of Rn Removal in HKUST-1

Geng,

Mao,

et al. 2023

J. Phys. Chem. C

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Kinetically driven island morphology in growth on strained Cu(100)

Khatri

Sabbar

Shim

et al. 2021

The Journal of Chemical Physics

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We study the effects of strain on the monomer and dimer diffusion mechanisms and island morphology during the growth of Cu on a biaxially strained Cu(100) substrate. We find an approximately linear dependence of the activation barriers on strain. In particular, while hopping is favored for compressive and/or small (<2%) tensile strain, for greater than 2% tensile strain, the exchange mechanism is favored. We then present the results of temperature-accelerated dynamics simulations of submonolayer growth at 200 K. For the case of 2% compressive strain we find that, as in previous kinetic Monte Carlo simulations of Cu/Ni(100) growth, the competition between island growth and multi-atom relaxation (“pop-out”) events leads to an island morphology with a mixture of open and closed steps. At slightly higher coverage, island coalescence then leads to elongated islands. However, annealing leads to a significant decrease in the number of open steps. In contrast, for the case of 8% tensile strain, only one large strongly anisotropic island is formed. Surprisingly, we find that despite the large strain, the island anisotropy is not due to energetics but is instead due to anisotropic attachment barriers that favor the exchange-mediated attachment of monomers to corners over close-packed step-edges. An explanation for the asymmetry in attachment barriers is provided. Our results provide a new general kinetic mechanism for the formation of anisotropic islands in the presence of isotropic diffusion and tensile strain.

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Step instabilities in Fe/Cu(100) growth

Shim

Amar

2017

Phys. Rev. Materials

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Improved scaling of temperature-accelerated dynamics using localization

Cited by 4 publications

References 53 publications

Water Unexpectedly Impacts Both Thermodynamics and Kinetics of Rn Removal in HKUST-1

Water Unexpectedly Impacts Both Thermodynamics and Kinetics of Rn Removal in HKUST-1

Kinetically driven island morphology in growth on strained Cu(100)

Step instabilities in Fe/Cu(100) growth

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