Giulia Galli

Melting of Diamond at High Pressure

Melting of diamond at high pressure and the properties of liquid carbon at pressures greater than 1 megabar were investigated with a first-principles molecular dynamics technique. The results indicate an increase of the diamond melting temperature with pressure, which is opposite to the behavior of silicon and germanium. This is contrary to long-held assumptions, but agrees with recent experiments, and has important implications for geology and astrophysics. As is the case for the solid phase of carbon at low temperature, which changes greatly with pressure from graphite to diamond, the structural and bonding properties of liquid carbon vary strongly with pressure.

Theoretical study of molten KSi

Molten potassium silicide (KSi) has been investigated with a first‐principles molecular dynamics technique. The system belongs to the class of I–IV alloys, which have been extensively studied in recent years in view of the anomalous behavior of their structural and thermodynamical properties compared to ideal solutions. A detailed analysis of the ionic trajectories obtained in our computer simulation shows that Zintl‐like ions (Si)4−4, present in the solid, tend to lose their identity in the liquid phase and that Si atoms form an extended network with two‐, three‐, and four‐fold coordinated sites. Also, the calculated diffusion constants and power spectra reflect the presence of a different kind of atomic arrangements attained by Si in the melt. The bond between K and Si, characterized in terms of nodal potential energy surfaces, is found to be partially ionic. Accordingly, the computed electronic density of states and electrical conductivity show that the liquid is a semiconductor. Our results can be use...

Structural properties of amorphous SiC via ab-initio molecular dynamics

We have investigated a-SiC at stoichiometric composition at room temperature using a first principles molecular dynamics technique. This method has proven to be very successful in predicting a variety of properties of disordered systems, amongst them a-C and a-Si. From our results, we analyzed the short range order of the system, in particular whether it is chemically ordered or has a random distribution of Si-C bonds and the different kind of bonding configurations attained by the two species.

Ab-Initio Study of Amorphous and Liquid Carbon

The bonded forms of carbon in solid and liquid states have considerable variations with many characteristics which make them interesting for a wide range of researchers1–4. Nevertheless, outstanding questions concerning the properties of both non-crystalline and liquid carbon are yet unanswered; in particular, knowledge of the structural and electronic properties of the low density disordered phases, the nature of the liquid state and the melting mechanism — despite systematic investigations4 of the carbon phase diagram carried out in different fields, such as condensed matter physics1, astrophysics2 and geology3.