Thermomechanical properties of graphene: valence force field model approach

摘要

Using the valence force field model of Perebeinos and Tersoff [Phys. Rev. B{\bf79}, 241409(R) (2009)], different energy modes of suspended graphenesubjected to tensile or compressive strain are studied. By carrying out MonteCarlo simulations it is found that: i) only for small strains ($|\varepsilon|\lessapprox 0.02$) the total energy is symmetrical in the strain, while itbehaves completely different beyond this threshold; ii) the important energycontributions 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 increaserapidly and beyond the buckling transition stretching and bending energies arefound to be constant; iv) from stretching-compressing simulations we calculatedthe Young modulus at room temperature 350$\pm3.15$\,N/m, which is in goodagreement with experimental results (340$\pm50$\,N/m) and with ab-initioresults [322-353]\,N/m; v) molar heat capacity is estimated to be24.64\,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 atfinite temperature; vii) the used valence force field model results in atemperature independent bending modulus for graphene, and viii) the Gruneisenparameter is estimated to be 0.64.