Strong anharmonicity in pristine graphene
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2018
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The thermodynamic coefficients of a free standing infinite graphene monolayer are calculated using
the quasi-classical unsymmetrized self-consistent field method (USF). The basic nonlinear integral
equations of this theory are solved numerically in the strong anharmonic approximation. The
isothermal and adiabatic elastic bulk moduli, the isochoric and isobaric heat capacities, the thermal
expansion, thermal pressure coefficient, and the macroscopic Gruneisen parameter are calculated in
terms of the derivatives of a specifically chosen interatomic potential function for different values of
stress and for temperatures ranging from below room temperature up to the point of loss of
thermodynamic stability. The nearest-neighbor distances vary from1.4Åto1.8Åfor zero stress.
Under stress, these distances decrease. At room temperature the molar heat capacities are
∼5.0Jmol−1K−1. The elasticitymoduli vary from15.0eVÅ-2 up to zero at the temperature of loss of
stability and are increased by stress. The thermal expansion coefficient has a strong dependence on the
temperature and is negative for temperatures lower than∼340K. For high temperatures it
monotonically increases and decreases with stress. The macroscopic Gruneisen parameter has a strong
nonlinear dependencewith temperature and is estimated in about 3.0 ¸ 3.7; at∼340Kits value
decreases to∼1.0Kand for even lower temperature it shows a peak and deep structure similar to what
has been earlier reported for fullereneC60.
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Palavras-chave
Anharmonicity, Graphene, Thermodynamic properties, Two-dimensional crystal
Citação
RABELO, J. N. Teixeira; CÂNDIDO, Ladir. Strong anharmonicity in pristine graphene. Journal of Physics Communications, Bristol, v. 2, p. 095013, 2018. DOI: 10.1088/2399-6528/aadd76. Disponívle em: https://iopscience.iop.org/article/10.1088/2399-6528/aadd76. Acesso em: 26 abr. 2023.