Starting with the molecular structure of α-RDX,the non-empirical full atom self-consistent force field( SCFF) for the explosive was derived via the first principles including electronic structure theory,intermolecular perturbation theory,and based on the SCFFphonon approach to calculating the anharmonic free energy,the isentropic locus for α-RDX was obtained,covering a pressure range from the ambient pressure to 55 GPa. The relationships between p( GPa) and V( cm~3·mol~(-1)),and between T( K) and V( cm~3·mo...