Molecular dynamics investigation of the thermomechanical behavior of monolayer GaN

JVN Sarma and R Chowdhury and R Jayaganthan, JOURNAL OF APPLIED PHYSICS, 113, 243504 (2013).

DOI: 10.1063/1.4812328

Molecular dynamics simulations are performed on monolayer gallium nitride to study their mechanical behavior at various temperatures in the range of 10 to 1700 K. The transition from brittle to ductile nature has been illustrated from the evolution of fracture at two different temperatures of 700 and 1300 K. Brittle to ductile transition temperatures TBDT are obtained from the plots of logarithm of yield stress and inverse temperature at different strain rates and compared qualitatively with the same system in the presence of single and diatomic vacancies. Logarithm of strain rate against inverse of TBDT thus obtained represents an Arrhenius plot, the slope of which corresponds to the activation energy of dislocation glide that is found to be approximately 2.0+/-0.05 eV for the present case. This suggests that the brittle to ductile transition is controlled by the dislocation mobility as in the case of other semiconductors like silicon and germanium. This behavior is found to be consistent with the presented underlying models. In addition, thermal conductivities are obtained over a temperature range of 300 to 2000K from the equilibrium Green-Kubo formulations and compared with the (25,0) nanotube that is generated from the same system of monolayer GaN. The values are found to be decreased in both the cases as compared to the bulk gallium nitride, and the reduction in the values of thermal conductivity can be attributed to the finite size effects, increased surface inelastic scattering, and change of phonon spectrum at low dimensions, respectively. (C) 2013 AIP Publishing LLC.

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