Solid–liquid transitions in homogenous ovalene, hexabenzocoronene and circumcoronene clusters: A molecular dynamics study

Chen, Dongping; Akroyd, Jethro; Mosbach, Sebastian; Opalka, Daniel; Kraft, Markus

doi:10.1016/j.combustflame.2014.07.025

Cited by 35 publications

(39 citation statements)

References 75 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The atom-centered point charges were parameterized for the MD simulation by a transferable electrostatic model for PAH molecules (48). An isotropic potential (isoPAHAP) was used for intermolecular C-C, C-H, and H-H interactions (49). We adapted the intramolecular potential parameters from the optimized, all atom potentials for liquid simulations (OPLS-AA) force field (50) for all angles.…”

Section: Methodsmentioning

confidence: 99%

Flame-formed carbon nanoparticles exhibit quantum dot behaviors

Liu

Singh

Saggese

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

We examine the quantum confinement in the photoemission ionization energy in air and optical band gap of carbon nanoparticles (CNPs). Premixed, stretched-stabilized ethylene flames are used to generate the CNPs reproducibly over the range of 4-23 nm in volume median diameter. The results reveal that flameformed CNPs behave like an indirect band gap material, and that the existence of the optical band gap is attributed to the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap in the polycyclic aromatic hydrocarbons comprising the CNPs. Both the ionization energy and optical band gap are found to follow closely the quantum confinement effect. The optical band gaps, measured both in situ and ex situ on the CNPs prepared in several additional flames, are consistent with the theory and the baseline data of CNPs from stretched-stabilized ethylene flames, thus indicating the observed effect to be general and that the particle size is the single most important factor governing the variation of the band gap of the CNPs studied. Cyclic voltammetry measurements and density functional theory calculations provide additional support for the quantum dot behavior observed. carbon nanoparticles | quantum dots | flames N anosized carbon grains composed of disordered polycyclic aromatic hydrocarbons (PAHs) are one of the most abundant forms of carbon material in nature (1). As a less-celebrated allotrope of carbon in comparison with fullerenes, nanotubes, and graphene, carbon nanoparticle (CNP) has its share of importance in a wide range of physical phenomena. Studies of interstellar emission spectra suggest that PAH dust grains or CNPs are ubiquitous in the interstellar media (2-5); and they are considered as the tracer of the star formation process (3, 6). CNPs are formed in flames during incomplete combustion. They are part of the soot-formation process. Mature soot or atmospheric black carbon particles often contain both elemental and organic carbon, the relative amounts of which vary by source (7). Soot impacts the global and region climate systems (8, 9) because of its light-absorbing properties (10, 11) and also as cloud condensation nuclei (12). CNPs 10-20 nm in size or fine carbon particles are themselves abundant in diesel exhausts (13). Their light-absorption properties and impact on climate forcing remain poorly characterized (14). As a material, however, CNPs have found their applications in photovoltaic and electrochemical devices, including perovskite solar cells in which flame CNPs act as a hole transfer medium (15).In contrast to the notion that soot, young or mature with respect to its growth in flames, is a broadband light absorber, recent studies have shown that CNPs several nanometers in size have well-defined optical band gaps or band edges (16)(17)(18). The band gap arises from the energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the constituent PAHs (18,19). While previous studies (16-18) explored the vari...

show abstract

Section: Methodsmentioning

confidence: 99%

Flame-formed carbon nanoparticles exhibit quantum dot behaviors

Liu

Singh

Saggese

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

View full text Add to dashboard Cite

show abstract

“…There have been a number of studies investigating theoretical aspects of PAH dimerisation as the initial step to particle nucleation. Sabbah et al [58] found that the equilibrium of pyrene dimerisation strongly favours the dissociation of the dimer at high temperature and that much larger PAHs, PAHs the size of circumcoronene, are required to be able to play a role in nucleation [59][60][61][62]. A key assumption made, however, is that dimerisation is governed by equilibrium kinetics.…”

Section: Resultsmentioning

confidence: 99%

Modelling PAH curvature in laminar premixed flames using a detailed population balance model

Yapp

Wells

Akroyd

et al. 2017

Combustion and Flame

Self Cite

View full text Add to dashboard Cite

A detailed population balance model, which includes the kinetic Monte Carloaromatic site (KMC-ARS) model for detailed polycyclic aromatic hydrocarbon (PAH) growth, is used to compute the Gauss curvature of PAHs in laminar premixed ethylene and benzene flames. Previous studies have found that capping of an embedded 5-member ring causes curvature in graphene edges. In this work, a capping process is added to the KMC-ARS model with the rate coefficient of the capping reaction taken from the work of You et al. [Proc. Combust. Inst., 33:685-692, 2011]. We demonstrate that the Gauss-Bonnet theorem can be used to derive a correlation between the number of 5-and 6-member rings in a PAH and its Gauss curvature (or radius of curvature), independent of where the 5-member ring is embedded within the PAH structure. Numerical simulation yields satisfactory results when compared to the experimentally determined Gauss curvature reported in the literature. Computed and experimental fringe length distributions are also compared and the results suggest that PAHs smaller than the size required for inception are able to condense onto particles.

show abstract

“…The relative orientation of aromatic rings within a PAH molecule is neglected at the CG level for simplicity and thus, the CG representations of all the PAH molecules under study are planar. It has been suggested to treat larger PAHs as rigid bodies due to high Debye temperature of their in‐plane vibrations . However, for smaller PAHs where the in‐plane vibrations are noticeable, the rigid molecule approximation needs to be validated, which we do in our simulations.…”

Section: Modeling and Simulationmentioning

confidence: 99%

“…It has been suggested to treat larger PAHs as rigid bodies due to high Debye temperature of their in-plane vibrations. [51] However, for smaller PAHs where the in-plane vibrations are noticeable, the rigid molecule approximation needs to be validated, which we do in our simulations. Each of the GB ellipsoid in a PAH molecule is represented by the corresponding center of mass coordinates and the orientation vector, which is the symmetry axis of the planar molecule, normal to its plane.…”

Section: Coarse-graining Schemementioning

confidence: 99%

“…However, the huge computational expense of such methods limits these investigations to either dimers or small clusters. Atomistic simulation provides access to comparatively larger length scales and allows the study of larger clusters and bulk systems . Such simulations have mostly relied on all‐atom force fields like optimized potentials for liquid simulations (OPLS), atomic multipole optimized energetics for biomolecular simulation (AMOEBA), molecular mechanics (MM3), and atomistic models such as anisotropic potential for PAH molecules (PAHAP), which are based on symmetry‐adapted perturbation theory.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Toward Transferable Coarse‐Grained Potentials for Poly‐Aromatic Hydrocarbons: A Force Matching Approach

Tripathy

Agarwal

Kumar

2018

Macro Theory & Simulations

View full text Add to dashboard Cite

Poly‐aromatic hydrocarbons (PAHs) have been the subject of numerous experimental investigations for their multitude of existence, from particulate soot to the vast cosmos. Given the structural peculiarity of PAHs, where aromatic moieties serve as the basic building blocks, a generalized coarse‐grained (CG) description befits and holds immense potential to investigate large‐scale PAH systems and their derivatives via CG simulation. Toward this, a minimal CG mapping scheme is proposed where a set of PAHs are modeled as planar molecules made up of oblate ellipsoids, which interact via uniaxial Gay–Berne (GB) potential. A force‐based systematic coarse‐graining approach is followed to extract the CG force field parameters. The resulting GB parameters are found to be either comparable or show definite trends as a function of molecular size. CG simulation is shown to retain the qualitative structural features of the underlying atomistic systems with multi‐fold decrease in computational cost. Accelerated equilibration of atomistic systems is shown to be achievable by MC simulations of CG systems followed by back‐mapping, where the atomistic structure is exactly reproduced.

show abstract

Solid–liquid transitions in homogenous ovalene, hexabenzocoronene and circumcoronene clusters: A molecular dynamics study

Cited by 35 publications

References 75 publications

Flame-formed carbon nanoparticles exhibit quantum dot behaviors

Flame-formed carbon nanoparticles exhibit quantum dot behaviors

Modelling PAH curvature in laminar premixed flames using a detailed population balance model

Toward Transferable Coarse‐Grained Potentials for Poly‐Aromatic Hydrocarbons: A Force Matching Approach

Contact Info

Product

Resources

About