Amorphous carbon (a-C) structures over a wide range of densities are generated by tight-binding molecular dynamics simulations using the recently developed environment-dependent carbon tight-binding potential. Our simulation results show that the relative concentration of the sp~2 and sp~3 bondings in the a-C samples changes systematically with the density of the samples. The a-C networks obtained by quenching the low density liquids consist of mostly three-fold coordinated atoms while the diamond-like tetrahedral a-C can be generated by quenching the high density (about 3.0g/cm~3) liquid carbon.
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