The Thermal Conductivity of Magnesite, Dolomite and Calcite as Determined by Molecular Dynamics Simulation

In this study, the phonon-based thermal conductivity of magnesite (MgCO3) and dolomite (CaMg(CO3)2) is calculated and compared with an earlier recent calculation on calcite (CaCO3). Equilibrium molecular dynamics simulation by way of the elegant Green-Kubo formalism is used for calculating the thermal conductivity. The thermal conductivity is investigated over a wide temperature range (from 200 K to 800 K) for all of the above mentioned materials. The most reliable potential parameters are used for characterising the interatomic interactions. In all of the models, two independent mechanisms are considered. The first is temperature independent, which is relevant to the acoustic short-range and optical phonons, and the other is temperature dependent, which is linked to the acoustic long-range phonons. In the study, the heat current autocorrelation function (HCACF) is calculated over the averages of the NPT, NVT and NVE ensembles in the x- and z- directions. In addition, it is shown that the optical, acoustic short- and long-range phonon modes are the main contributors to the decomposition model of the thermal conductivity. In a further investigation, the effects of the computational cell sizes on the thermal conductivity are investigated with five different simulation blocks containing 30, 240, 810, 1920 and 6480 atoms. Finally, this research provides a comparison of the thermal conductivity from this study and experimental studies: they are in good agreement.

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Thermal Conductivity of Individual Single-Wall Carbon Nanotubes

Journal of Heat Transfer ◽

10.1115/1.2717242 ◽

2006 ◽

Vol 129 (6) ◽

pp. 705-716 ◽

Cited By ~ 215

Author(s):

Jennifer R. Lukes ◽

Hongliang Zhong

Keyword(s):

Experimental Data ◽

Thermal Conductivity ◽

Carbon Nanotubes ◽

Molecular Dynamics ◽

Molecular Dynamics Simulation ◽

Dynamics Simulation ◽

Single Wall Carbon Nanotubes ◽

Heat Current ◽

Single Wall Carbon ◽

Simulation Methodology

Despite the significant amount of research on carbon nanotubes, the thermal conductivity of individual single-wall carbon nanotubes has not been well established. To date only a few groups have reported experimental data for these molecules. Existing molecular dynamics simulation results range from several hundred to 6600 W∕m K and existing theoretical predictions range from several dozens to 9500 W∕m K. To clarify the several-order-of-magnitude discrepancy in the literature, this paper utilizes molecular dynamics simulation to systematically examine the thermal conductivity of several individual (10, 10) single-wall carbon nanotubes as a function of length, temperature, boundary conditions and molecular dynamics simulation methodology. Nanotube lengths ranging from 5 nm to 40 nm are investigated. The results indicate that thermal conductivity increases with nanotube length, varying from about 10 W∕m to 375 W∕m K depending on the various simulation conditions. Phonon decay times on the order of hundreds of fs are computed. These times increase linearly with length, indicating ballistic transport in the nanotubes. A simple estimate of speed of sound, which does not require involved calculation of dispersion relations, is presented based on the heat current autocorrelation decay. Agreement with the majority of theoretical/computational literature thermal conductivity data is achieved for the nanotube lengths treated here. Discrepancies in thermal conductivity magnitude with experimental data are primarily attributed to length effects, although simulation methodology, stress, and intermolecular potential may also play a role. Quantum correction of the calculated results reveals thermal conductivity temperature dependence in qualitative agreement with experimental data.

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Phonon Thermal Conductivity of the Cubic and Monoclinic Phases of Zirconia by Molecular Dynamics Simulation

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.843.110 ◽

2020 ◽

Vol 843 ◽

pp. 110-115

Author(s):

Leila Momenzadeh ◽

Irina V. Belova ◽

Graeme E. Murch

Keyword(s):

Experimental Data ◽

Thermal Conductivity ◽

Molecular Dynamics ◽

Molecular Dynamics Simulation ◽

Lattice Thermal Conductivity ◽

Dynamics Simulation ◽

Heat Current ◽

Phonon Thermal Conductivity ◽

Low Thermal Conductivity ◽

Two Phases

Zirconia has a number of remarkable properties, including a very low thermal conductivity. In this research, the phonon thermal conductivity of two phases (cubic and monoclinic) of zirconia (ZrO2) are calculated. For this purpose, an equilibrium molecular dynamics simulation employing the Green-Kubo formalism is used. The results are presented in detail over a wide temperature range, from 100 K to 2400 K and 100 K to 1400 K for the above-mentioned structures, respectively, with a 100K temperature step. The temperature dependence of the equilibrium atomic volume demonstrated a reasonable agreement with the experimental data. Moreover, the lattice thermal conductivity was calculated by analysing the heat current autocorrelation function. The results showed that zirconia has a low thermal conductivity that is dependent on the temperature. It was also shown that the lattice thermal conductivity of the two phases of zirconia can be decomposed into three contributions due to the acoustic shortrange and long-range phonon and optical phonon modes. Finally, the results from this research are compared with the available experimental data.

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