Effects of pressure on atomic and electronic structure and crystallization dynamics of amorphous Ge2Sb2Te5

We investigate the effects of pressure on atomic and electronic structures of amorphous Ge2Sb2Te5 using first-principles methods. The supercell volume is varied from 0.94 to 1.13 times the nominal amorphous volume in melt-quench simulations. When the simulation cell is compressed, we find that the energy gap is reduced and the number of localized in-gap states is increased. These results indicate that pressurized amorphous Ge2Sb2Te5 exhibits better conduction than Ge2Sb2Te5 formed under stress-free conditions. We also find that the positive pressure increases the densities of fourfold rings in amorphous Ge2Sb2Te5, shifting the local order toward the crystalline phase. Consistently, fast crystallization is identified for compressed amorphous Ge2Sb2Te5.