Spectroscopy of phonon modes of a single-wall armchair carbon nanotube using measurements of nonlinear conductance: Theory

We investigate thermal transport in water/carbon nanotube (CNT) composite systems using molecular dynamics simulations. Carbon-carbon interactions are modeled using the second-generation REBO potential, water-water interactions are modeled using the TIP4P potential, and carbon-water interactions are modeled using a Lennard-Jones potential. The thermal conductivities of empty and water-filled CNTs with diameters between 0.83 nm and 1.66 nm are predicted using molecular dynamics simulation and a direct application of the Fourier law. For empty CNTs, the thermal conductivity decreases with increasing CNT diameter. As the CNT length approaches 1 micron, a length-independent thermal conductivity is obtained, indicative of diffusive phonon transport. When the CNTs are filled with water, the thermal conductivity decreases compared to the empty CNTs and transitions to diffusive phonon transport at shorter lengths. To understand this behavior, we calculate the spectral energy density of the empty and water-filled CNTs and calculate the mode-specific group velocities, relaxation times, and thermal conductivity. For the empty 1.10 nm diameter CNT, we show that the acoustic phonon modes account for 65 percent of the total thermal conductivity. This behavior is attributed to their long mean-free paths. When the CNT is filled with water, interactions with the water molecules shorten the acoustic mode mean-free path and lower the overall CNT thermal conductivity.

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Comparative analysis of electron-phonon relaxation in a semiconducting carbon nanotube and a PbSe quantum dot

Pure and Applied Chemistry ◽

10.1351/pac200880071433 ◽

2008 ◽

Vol 80 (7) ◽

pp. 1433-1448 ◽

Cited By ~ 4

Author(s):

Bradley F. Habenicht ◽

Svetlana V. Kilina ◽

Oleg V. Prezhdo

Keyword(s):

Carbon Nanotube ◽

Quantum Dot ◽

Density Functional ◽

Low Frequency ◽

Electronic Energy ◽

Relaxation Processes ◽

Phonon Modes ◽

Lorentzian Line ◽

Line Shapes ◽

Optical Modes

The key features of the phonon-induced relaxation of electronic excitations in the (7,0) zig-zag carbon nanotube (CNT) and the Pb16Se16 quantum dot (QD) are contrasted using a time-domain ab initio density functional theory (DFT) simulation. Upon excitation from the valence to the conduction band (CB), the electrons and holes nonradiatively decay to the band-edge in both materials. The paper compares the electronic structure, optical spectra, important phonon modes, and decay channels in the CNT and QD. The relaxation is faster in the CNT than in the QD. In the PbSe QD, the electronic energy decays by coupling to low-frequency acoustic modes. The decay is nonexponential, in agreement with non-Lorentzian line-shapes observed in optical experiments. In contrast to the QD, the excitation decay in the CNT occurs primarily via high-frequency optical modes. Even though the holes have a higher density of states (DOS), they relax more slowly than the electrons, due to better coupling to low-frequency vibrations. Further, the expected phonon bottleneck is not observed in the QD, as rationalized by a high density of optically dark states. The same argument applies to the CNT. The computed results agree well with experimentally measured ultrafast relaxation time-scales and provide a unique atomistic picture of the electron-phonon relaxation processes.

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THE EFFECT OF THE DIAMETER ON THE SPECIFIC HEAT OF CARBON NANOTUBES

International Journal of Nanoscience ◽

10.1142/s0219581x0900575x ◽

2009 ◽

Vol 08 (01n02) ◽

pp. 35-38 ◽

Cited By ~ 4

Author(s):

MAHMOUD JAFARI ◽

MAJID VAEZZADEH ◽

LEILA BOHLOLI OSKOEI

Keyword(s):

Carbon Nanotubes ◽

Carbon Nanotube ◽

Specific Heat ◽

Acoustic Phonon ◽

Phonon Modes ◽

Specific Temperature

Specific heat of carbon nanotube (CNT) is affected by its diameter. Increasing of the CNTs diameter increases its specific heat. This phenomenon is due to transversal acoustic phonon modes. The contribution to specific heat from TA modes varies linearly with temperature and becomes saturated after specific temperature. In this paper, the effect of CNTs diameter on the specific heat is theoretically simulated. The result indicates that transversal phonon modes play an important role in the increasing of specific heat with respect to the diameter.

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Thermal conductivity of multi-walled carbon nanotube sheets: radiation losses and quenching of phonon modes

Nanotechnology ◽

10.1088/0957-4484/21/3/035709 ◽

2009 ◽

Vol 21 (3) ◽

pp. 035709 ◽

Cited By ~ 165

Author(s):

Ali E Aliev ◽

Marcio H Lima ◽

Edward M Silverman ◽

Ray H Baughman

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotube ◽

Phonon Modes ◽

Radiation Losses ◽

Multi Walled Carbon Nanotube

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Thermal Conductivity of Water/Carbon Nanotube Composite Systems: Insights From Molecular Dynamics Simulations

Volume 2: Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Computational Heat Transfer ◽

10.1115/ht2009-88029 ◽

2009 ◽

Author(s):

J. A. Thomas ◽

R. M. Iutzi ◽

A. J. H. McGaughey

Keyword(s):

Thermal Conductivity ◽

Molecular Dynamics ◽

Carbon Nanotube ◽

Effective Thermal Conductivity ◽

Linear Response Theory ◽

Phonon Transport ◽

Dynamics Simulation ◽

Phonon Modes ◽

Composite Systems ◽

Dynamics Simulations

The effective thermal conductivity of water/carbon nanotube (CNT) composite systems is predicted using molecular dynamics simulation. Both empty and water-filled CNTs with diameters ranging from 0.83 nm to 1.26 nm are considered. Using a direct application of the Fourier law, we explore the transition to diffusive phonon transport with increasing CNT length and identify the correlation between CNT diameter and fully-diffusive thermal conductivity. Using Green-Kubo linear response theory, we explore how the thermal conductivity of water inside CNT varies with tube diameter. We predict the effective thermal conductivity of the composite systems and examine how the phonon modes in the CNT are affected by interactions with the water molecules.

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Energy Loss in Carbon Nanotube Beam Oscillators due to Anelastic Relaxation

Journal of Engineering Materials and Technology ◽

10.1115/1.4006506 ◽

2012 ◽

Vol 134 (3) ◽

Cited By ~ 2

Author(s):

Zhong Zhou ◽

Vijay K. Vasudevan ◽

Dong Qian

Keyword(s):

Carbon Nanotube ◽

Energy Dissipation ◽

Analytical Formula ◽

Analytical Prediction ◽

Q Factor ◽

Phonon Modes ◽

Additional Energy ◽

Major Mechanism ◽

Q Factors ◽

Quality Factor Q

We present a semi-analytical approach to study the energy dissipation in carbon nanotube (CNT) beam oscillators under gigahertz excitation. The energy dissipation properties are quantified by the quality factor (Q factor) and associated anelastic properties. Our study reveals that the Q factor is related to the tube radius through an inverse relation for both single walled CNTs (SWCNTs) and multiwalled CNTs (MWCNTs) beam oscillators. At frequency close to the resonance range, significant energy dissipation is observed due to the activation of phonon modes that serve as a major mechanism for energy dissipation in SWCNTs. For MWCNTs, a registration dependent potential (RDP) is introduced to study the effect of intertube registration. Interlayer friction arising from the π bond overlap is shown to contribute significantly to the additional energy dissipation. Based on the extensive simulation studies, an analytical formula for estimating the Q factors of MWCNTs is proposed. Validation of the analytical prediction with the available experimental data yields a good agreement and quantifies the roles of different factors contributing to the energy dissipation through anelastic relaxation.

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