I am performing SCF calculations using Quantum Espresso for crystalline materials to determine the band gaps and energies. A sample output for one of the crystals is shown below.
highest occupied, lowest unoccupied level (ev): 9.2589 13.2824 ! total energy = -392.86522200 Ry estimated scf accuracy < 0.00000034 Ry The total energy is the sum of the following terms: one-electron contribution = -87.58728570 Ry hartree contribution = 68.54396895 Ry xc contribution = -87.05600859 Ry ewald contribution = -248.69804485 Ry one-center paw contrib. = -38.06785182 Ry -> PAW hartree energy AE = 0.00000000 Ry -> PAW hartree energy PS = 0.00000000 Ry -> PAW xc energy AE = 0.00000000 Ry -> PAW xc energy PS = 0.00000000 Ry -> total E_H with PAW = 68.54396895 Ry -> total E_XC with PAW = -87.05600859 Ry
I would like to know if the total energy here is an absolute or a relative value. Also, does lower total energy always imply more stability, or do I have to divide the energy by the number of atoms to compare the stabilities of different crystals?