Influence of the exchange and correlation functional on the structure of amorphous InSb and In3SbTe2 compounds.

We have investigated the structural, vibrational, and electronic properties of the amorphous phase of InSb and In3SbTe2 compounds of interest for applications in phase change non-volatile memories. Models of the amorphous phase have been generated by quenching from the melt by molecular dynamics simulations based on density functional theory. In particular, we have studied the dependence of the structural properties on the choice of the exchange-correlation functional.

Effective kinetic phase diagrams.

The composition of a solid solution that is growing at conditions well away from equilibrium is not prescribed by equilibrium thermodynamics, but is determined kinetically. It depends both on the surface kinetics and on the transport of mass and heat to and away from the solidification front. In previous work, we have formulated a model for the kinetic or nonequilibrium segregation taking place at the solidification front enabling the construction of kinetic phase diagrams, which gives the growth composition of a solid solution as a function of the liquid composition and undercooling at the surface.

Modeling the phase diagram of carbon.

We determined the phase diagram involving diamond, graphite, and liquid carbon using a recently developed semiempirical potential. Using accurate free-energy calculations, we computed the solid-solid and solid-liquid phase boundaries for pressures and temperatures up to 400 GPa and 12 000 K, respectively. The graphite-diamond transition line that we computed is in good agreement with experimental data, confirming the accuracy of the employed empirical potential.