Permeation of Fullerenes through Graphynes: Theoretical Design of Nanomechanical Oscillators

Abstract

Carbon allotropes such as fullerenes, carbon nanotubes (CNTs), and graphene have shown great promise for device applications in recent times. Nanomechanical oscillators based on CNTs are well-explored theoretically as well as experimentally. Investigations on the motion of C60 through CNTs have revealed oscillator frequencies of up to 74 GHz. However, the absence of mature technology in the terahertz regime has resulted in the so-called terahertz gap. On the basis of an analysis of the permeation of fullerenes through the nanopores of graphynes (GYs), herein, we report the theoretical design of nanomechanical oscillators in the 0.1–0.5 THz regime. The design strategy involves employing electronic structure methods as well as atomistic model potentials to probe the permeation process of a set of fullerenes, namely, C20, C42, C50, C60, C70, and C84 through the triangular and the rhombus-like nanopores of γ-GY-N (N = 4–6) and r-GY-N (N = 4–5), respectively. Considering the results from the electronic structure methods as a benchmark, we adopt a fitting procedure to extract the optimal values of the parameters in the atomistic model potentials that could be useful for researchers performing force field calculations on fullerene–graphyne systems. Our findings indicate that a discrete atomistic potential of the improved Lennard-Jones type can describe the permeation process leading to the oscillatory response with reasonable accuracy at a computational cost much lower than the electronic structure calculations.

The Necessity of Periodic Boundary Conditions for the Accurate Calculation of Crystalline Terahertz Spectra

“…95,96 However, many recent studies have used ab initio gas-phase simulations to assign experimental condensed phase terahertz spectra, with varying levels of apparent success. [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] It is important to note that in almost all of these cases the discussed 'agreement' with experiment is largely based upon the position of calculated vibrational transitions, with little focus placed upon the accuracy of the predicted mode-types -critical for gaining deeper insight into the way terahertz motions influence bulk material properties, for example. Therefore, this work aims to asses how gas-phase simulations reproduce terahertz spectra, as well as predicting the corresponding vibrational mode-types.…”

The Necessity of Periodic Boundary Conditions for the Accurate Calculation of Crystalline Terahertz Spectra

“…29 However, due to the complexity and (assumed) increased computational cost of periodic boundary condition simulations, gas-phase calculations involving clusters of molecules have been employed in studies describing terahertz vibrations, with varying levels of apparent success. [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] It is important to note that, in general, such assessment is based solely on the position of the calculated transitions, with little focus on the actual motions involved or their accuracy. However, there is a lack of comparison in the literature between these methods, and therefore this work aims to assess how gas-phase simulations perform in regard to reproducing not only the experimental terahertz spectra, but also the prediction of the vibrational mode-types.…”

Modeling the Adsorption of Polycyclic Aromatic Hydrocarbons on Graphynes: An Improved Lennard-Jones Formulation

“…The initial set of ε and r m values for hydrogen−hydrogen interactions are chosen from a previous literature report. 54,61 For interactions between dissimilar atoms, the parameters are obtained by the Lorentz−Berthelot mixing rules 62 as given below…”

“…51−53 Our group has reported a parametrization of the ILJ potential to analyze the permeation of fullerenes through GYs leading to a nanomechanical oscillatory response. 54 Herein, we develop and implement an ILJ potential formulation to model the adsorption of cata-condensed and peri-condensed PAHs on α, β, γ, and rhombic forms of GYs. Our analysis comprises the following steps: (i) parametrization of the ILJ potential using benchmark electronic structure calculations, (ii) validation of the parametrized ILJ potential, (iii) analysis of the potential energy hypersurfaces for adsorption using the parametrized ILJ potential, and (iv) establishment of the predicted features with electronic structure calculations on selected PAH−GY complexes.…”

“…The model was shown to predict the structures of magic number clusters of benzene and coronene. The ILJ potential has been extensively used in recent times for modeling intermolecular interactions involving GYs with potential applications in water desalination, gas storage and separation, energy storage, etc . − Our group has reported a parametrization of the ILJ potential to analyze the permeation of fullerenes through GYs leading to a nanomechanical oscillatory response . Herein, we develop and implement an ILJ potential formulation to model the adsorption of cata-condensed and peri-condensed PAHs on α, β, γ, and rhombic forms of GYs.…”