Thermomechanical properties of graphene: valence force field model approach
(Mar 3, 2012)Abstract
Using the valence force field model of Perebeinos and Tersoff Phys. Rev. B
\bf79, 241409(R) (2009), different energy modes of suspended graphene
subjected to tensile or compressive strain are studied. By carrying out Monte
Carlo simulations it is found that: i) only for small strains (\$|\varepsilon|
0.02\$) the total energy is symmetrical in the strain, while it
behaves completely different beyond this threshold; ii) the important energy
contributions in stretching experiments are stretching, angle bending,
out-of-plane term and a term that provides repulsion against \$\pi-\pi\$
misalignment; iii) in compressing experiments the two latter terms increase
rapidly and beyond the buckling transition stretching and bending energies are
found to be constant; iv) from stretching-compressing simulations we calculated
the Young modulus at room temperature 350\$\pm3.15\$\,N/m, which is in good
agreement with experimental results (340\$\pm50\$\,N/m) and with ab-initio
results 322-353\,N/m; v) molar heat capacity is estimated to be
24.64\,J/mol\$^-1\$K\$^-1\$ which is comparable with the Dulong-Petit value,
i.e. 24.94\,J/mol\$^-1\$K\$^-1\$ and is almost independent of the strain; vi)
non-linear scaling properties are obtained from height-height correlations at
finite temperature; vii) the used valence force field model results in a
temperature independent bending modulus for graphene, and viii) the Gruneisen
parameter is estimated to be 0.64.