Do SiO2 and carbon-doped SiO2 nanoparticles melt? Insights from QM/MD simulations and ramifications regarding carbon nanotube growth

Page, Alister J.; Chandrakumar, K. R. S.; Irle, Stephan; Morokuma, Keiji

doi:10.1016/j.cplett.2011.01.075

Cited by 8 publications

(20 citation statements)

References 32 publications

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“…The occupancies of molecular orbitals close to the Fermi level were therefore not necessarily integer-occupied; instead they were described using a Fermi-Dirac distribution function of the orbital 5 energy. Such an electron smearing approach has been used extensively by our group in the context of nanoscale self-assembly 29,[34][35][36][49][50][51][52][53] and is also standard practice in traditional first principles-based MD …”

Section: Quantum Chemical Methodsmentioning

confidence: 99%

Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al₂O₃ Catalysts via CH₄ Chemical Vapor Deposition

Page

Saha

et al. 2015

J. Am. Chem. Soc.

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We present quantum chemical simulations demonstrating how single-walled carbon nanotubes (SWCNTs) form, or "nucleate", on the surface of Al2O3 nanoparticles during chemical vapor deposition (CVD) using CH4. SWCNT nucleation proceeds via the formation of extended polyyne chains that only interact with the catalyst surface at one or both ends. Consequently, SWCNT nucleation is not a surface-mediated process. We demonstrate that this unusual nucleation sequence is due to two factors. First, the π interaction between graphitic carbon and Al2O3 is extremely weak, such that graphitic carbon is expected to desorb at typical CVD temperatures. Second, hydrogen present at the catalyst surface actively passivates dangling carbon bonds, preventing a surface-mediated nucleation mechanism. The simulations reveal hydrogen's reactive chemical pathways during SWCNT nucleation and that the manner in which SWCNTs form on Al2O3 is fundamentally different from that observed using "traditional" transition metal catalysts.

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Section: Quantum Chemical Methodsmentioning

confidence: 99%

Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al₂O₃ Catalysts via CH₄ Chemical Vapor Deposition

Page

Saha

et al. 2015

J. Am. Chem. Soc.

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“…At all times, the Lindemann index revealed that the SiO 2 nanoparticle existed as a solid phase structure. Moreover, QM/MD relaxation of this nanoparticle at elevated temperatures (up to 3000 K) indicated that nanoparticle SiO 2 decomposes from the solid phase at sufficiently high temperatures (Page et al, 2011a). This sublimative phenomenon here rules out the VLS mechanism as an explanation of SiO 2 -catalysed SWNT nucleation and growth entirely.…”

Section: A New Breed Of Catalysts: Swnt Nucleation On Sio 2 Sic and Simentioning

confidence: 83%

“…These QM/MD investigations will be the focus of this section. QM/MD simulations of methane CVD on SiO 2 nanoparticles at 1200 K (Page et al, 2011b) is outlined in Fig. 8.…”

Section: A New Breed Of Catalysts: Swnt Nucleation On Sio 2 Sic and Simentioning

confidence: 99%

Mechanisms of Single-Walled Carbon Nanotube Nucleation, Growth and Chirality-Control: Insights from QM/MD Simulations

Page¹,

Chandrakumar²,

Wang³

et al. 2011

Electronic Properties of Carbon Nanotubes

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“…At all times, the Lindemann index revealed that the SiO 2 nanoparticle existed as a solid-phase structure. Moreover, QM/MD relaxation of this nanoparticle at elevated temperatures (up to 3,000 K) indicated that nanoparticle SiO 2 decomposes from the solid phase at sufficiently high temperatures [212]. This sublimative phenomenon here rules out the VLS mechanism as an explanation of SiO 2 -catalyzed SWCNT nucleation and growth entirely.…”

Section: Nucleation From Nonmetal Nanoparticlesmentioning

confidence: 93%

“…Si-based materials, and in particular SiO 2 , have been remarkably successful in this respect. Yet it has only been since 2010 that the atomistic mechanisms of SiO 2 -, SiC-, and Si-catalyzed SWCNT nucleation have been clarified [211,212]. These QM/MD investigations will be the focus of this section.…”

Section: Nucleation From Nonmetal Nanoparticlesmentioning

confidence: 98%

Atomistic Mechanism of Carbon Nanostructure Self-Assembly as Predicted by Nonequilibrium QM/MD Simulations

Irle

Page

Saha

et al. 2012

Practical Aspects of Computational Chemistry II

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We review our quantum chemical molecular dynamics (QM/MD)-based studies of carbon nanostructure formation under nonequilibrium conditions that were conducted over the past 10C years. Fullerene, carbon nanotube, and graphene formation were simulated on the nanosecond time scale, considering experimental conditions as closely as possible. An approximate density functional method was employed to compute energies and gradients on the fly in direct MD simulations, while the simulated systems were pushed away from equilibrium via carbon concentration or temperature gradients. We find that carbon nanostructure formation from feedstock particles involves a phase transition of sp to sp 2 carbon phases, which begins with the formation of Y-junctions, followed by a nucleus consisting of pentagons, hexagons, and heptagons. The dominance of hexagons in the synthesized

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Do SiO2 and carbon-doped SiO2 nanoparticles melt? Insights from QM/MD simulations and ramifications regarding carbon nanotube growth

Cited by 8 publications

References 32 publications

Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al₂O₃ Catalysts via CH₄ Chemical Vapor Deposition

Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al₂O₃ Catalysts via CH₄ Chemical Vapor Deposition

Mechanisms of Single-Walled Carbon Nanotube Nucleation, Growth and Chirality-Control: Insights from QM/MD Simulations

Atomistic Mechanism of Carbon Nanostructure Self-Assembly as Predicted by Nonequilibrium QM/MD Simulations

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Do SiO2 and carbon-doped SiO2 nanoparticles melt? Insights from QM/MD simulations and ramifications regarding carbon nanotube growth

Cited by 8 publications

References 32 publications

Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al2O3 Catalysts via CH4 Chemical Vapor Deposition

Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al2O3 Catalysts via CH4 Chemical Vapor Deposition

Mechanisms of Single-Walled Carbon Nanotube Nucleation, Growth and Chirality-Control: Insights from QM/MD Simulations

Atomistic Mechanism of Carbon Nanostructure Self-Assembly as Predicted by Nonequilibrium QM/MD Simulations

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Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al₂O₃ Catalysts via CH₄ Chemical Vapor Deposition

Quantum Chemical Simulation of Carbon Nanotube Nucleation on Al₂O₃ Catalysts via CH₄ Chemical Vapor Deposition