We present a scheme to compute the thermodynamic properties and the phase stability of materials based on parameter-free microscopic quantum theory. Taking Si as an example we show that properties like the specific entropy, volume, and heat capacity can be accurately calculated for various phases such as solid, liquid, and amorphous. In particular this allows us to accurately locate phase boundary in the full p-T diagram as well as to elucidate macroscopic thermodynamic properties of materials in terms of microscopic viewpoint.