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Phonon properties of graphene derived from molecular dynamics simulations.

Koukaras EN, Kalosakas G, Galiotis C, Papagelis K - Sci Rep (2015)

Bottom Line: The method is promising for systems with large scale periodicity, accounts for anharmonic effects and non-bonding interactions with a general environment, and it is applicable under finite temperatures.The potentials used show diverse behaviour.The Tersoff-2010 potential exhibits the most systematic and physically sound behaviour in this regard, and gives a first-order temperature coefficient of χ = -0.05 cm(-1)/K for the Γ-E2g shift in agreement with reported experimental values.

View Article: PubMed Central - PubMed

Affiliation: Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Stadiou Street, Platani, Patras, 26504 Greece.

ABSTRACT
A method that utilises atomic trajectories and velocities from molecular dynamics simulations has been suitably adapted and employed for the implicit calculation of the phonon dispersion curves of graphene. Classical potentials widely used in the literature were employed. Their performance was assessed for each individual phonon branch and the overall phonon dispersion, using available inelastic x-ray scattering data. The method is promising for systems with large scale periodicity, accounts for anharmonic effects and non-bonding interactions with a general environment, and it is applicable under finite temperatures. The temperature dependence of the phonon dispersion curves has been examined with emphasis on the doubly degenerate Raman active Γ-E2g phonon at the zone centre, where experimental results are available. The potentials used show diverse behaviour. The Tersoff-2010 potential exhibits the most systematic and physically sound behaviour in this regard, and gives a first-order temperature coefficient of χ = -0.05 cm(-1)/K for the Γ-E2g shift in agreement with reported experimental values.

No MeSH data available.


Related in: MedlinePlus

Temperature dependence of graphene’s phonon dispersion curves for the Tersoff-2010 potential.Data points for temperatures T = 60 K, T = 500 K and T = 1500 K are denoted by solid symbols, crosses and ×-marks, respectively. Plot (b) focuses on the optical branches, for which the temperature dependence is most notable. Open symbols in (a) correspond to experimental values taken from Refs 30,31.
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f4: Temperature dependence of graphene’s phonon dispersion curves for the Tersoff-2010 potential.Data points for temperatures T = 60 K, T = 500 K and T = 1500 K are denoted by solid symbols, crosses and ×-marks, respectively. Plot (b) focuses on the optical branches, for which the temperature dependence is most notable. Open symbols in (a) correspond to experimental values taken from Refs 30,31.

Mentions: To further examine the effects of temperature on the vibrational response of graphene we calculated the dispersion curves using the Tersoff-2010 potential for temperatures T = 60 K, 500 K, and 1500 K, which we show in Fig. 4. We note that the melting point of graphene employing this potential is around 2100 K. A stronger temperature dependence is observed on the optical branches. In Fig. 4b we focus on the optical branches, where it can be seen that upon increase of temperature the frequencies soften by as much as 75 cm−1 in this temperature range. The acoustic branches in the vicinity of Γ remain unaffected by changes in temperature. In the vicinity of the high symmetry points K and M a decrease in the frequencies of the acoustic branches is noted at most by 40 cm−1 in the considered temperature range.


Phonon properties of graphene derived from molecular dynamics simulations.

Koukaras EN, Kalosakas G, Galiotis C, Papagelis K - Sci Rep (2015)

Temperature dependence of graphene’s phonon dispersion curves for the Tersoff-2010 potential.Data points for temperatures T = 60 K, T = 500 K and T = 1500 K are denoted by solid symbols, crosses and ×-marks, respectively. Plot (b) focuses on the optical branches, for which the temperature dependence is most notable. Open symbols in (a) correspond to experimental values taken from Refs 30,31.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4551956&req=5

f4: Temperature dependence of graphene’s phonon dispersion curves for the Tersoff-2010 potential.Data points for temperatures T = 60 K, T = 500 K and T = 1500 K are denoted by solid symbols, crosses and ×-marks, respectively. Plot (b) focuses on the optical branches, for which the temperature dependence is most notable. Open symbols in (a) correspond to experimental values taken from Refs 30,31.
Mentions: To further examine the effects of temperature on the vibrational response of graphene we calculated the dispersion curves using the Tersoff-2010 potential for temperatures T = 60 K, 500 K, and 1500 K, which we show in Fig. 4. We note that the melting point of graphene employing this potential is around 2100 K. A stronger temperature dependence is observed on the optical branches. In Fig. 4b we focus on the optical branches, where it can be seen that upon increase of temperature the frequencies soften by as much as 75 cm−1 in this temperature range. The acoustic branches in the vicinity of Γ remain unaffected by changes in temperature. In the vicinity of the high symmetry points K and M a decrease in the frequencies of the acoustic branches is noted at most by 40 cm−1 in the considered temperature range.

Bottom Line: The method is promising for systems with large scale periodicity, accounts for anharmonic effects and non-bonding interactions with a general environment, and it is applicable under finite temperatures.The potentials used show diverse behaviour.The Tersoff-2010 potential exhibits the most systematic and physically sound behaviour in this regard, and gives a first-order temperature coefficient of χ = -0.05 cm(-1)/K for the Γ-E2g shift in agreement with reported experimental values.

View Article: PubMed Central - PubMed

Affiliation: Institute of Chemical Engineering Sciences, Foundation of Research and Technology-Hellas (FORTH/ICE-HT), Stadiou Street, Platani, Patras, 26504 Greece.

ABSTRACT
A method that utilises atomic trajectories and velocities from molecular dynamics simulations has been suitably adapted and employed for the implicit calculation of the phonon dispersion curves of graphene. Classical potentials widely used in the literature were employed. Their performance was assessed for each individual phonon branch and the overall phonon dispersion, using available inelastic x-ray scattering data. The method is promising for systems with large scale periodicity, accounts for anharmonic effects and non-bonding interactions with a general environment, and it is applicable under finite temperatures. The temperature dependence of the phonon dispersion curves has been examined with emphasis on the doubly degenerate Raman active Γ-E2g phonon at the zone centre, where experimental results are available. The potentials used show diverse behaviour. The Tersoff-2010 potential exhibits the most systematic and physically sound behaviour in this regard, and gives a first-order temperature coefficient of χ = -0.05 cm(-1)/K for the Γ-E2g shift in agreement with reported experimental values.

No MeSH data available.


Related in: MedlinePlus