Phase equilibrium(2) S.J.T.U. Phase Transformation and Applications For an ideal gas AG=RT In P2 Diamond P g T=Constant Graphite For an incompressible solid Po Equilibrium pressure △G=Y(p2-P1) Pressure- Figure 4.3 Specific Gibbs free energy versus pressure at con- stant temperature for graphite and diamond. For an compressible solid AG=[l-exp(-Bp】 PO is taken as zero Compressibility coefficient at constant temperature SJTU Thermodynamics of Materials Spring2007©X.J.Jin Lecture 7 equilibrium IPhase Transformation and Applications S. J. T. U. SJTU Thermodynamics of Materials Spring 2007 © X. J. Jin Lecture 7 equilibrium I Phase equilibrium (2) For an ideal gas 1 2 ln p p =Δ RTG For an incompressible solid )( 120 Δ = − ppVG For an compressible solid [ ] ( ) p V G T T β β exp1 −−=Δ 0 P0 is taken as zero Compressibility coefficient at constant temperature