We present a scheme to compute the thermodynamic properties and the phase stability of materials based on parameter-free microscopic quantum theory. Taking silicon as an example we show that properties like the specific entropy, the specific volume, or the heat capacity of a solid and a liquid can be calculated accurately. In particular, we can locate the solid-liquid phase boundary and compute how thermodynamic properties change upon melting. This greatly extends the range of first-principles predictions of materials properties.

• Received 11 July 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.1823