Localized electronic and vibrational states in amorphous diamond

Amorphous diamond structures are generated by quenching high-density high-temperature liquid carbon using tight-binding molecular-dynamics simulations. We show that the generated amorphous diamond structures are predominated by strong tetrahedral bonds with the sp³ bonding fraction as high as 97%, thus exhibit an ultra-high incompressibility and a wide band gap close to those of crystalline diamond. A small amount of sp² bonding defects in the amorphous sample contributes to localized electronic states in the band gap while large local strain gives rise to localization of vibrational modes at both high and low frequency regimes.