Thank you all very much.
Thank Postnikov answer my basic questions. and I am very sorry that I did not describe the problem clearly. Take another example to describe the problem, step 1, calculate DOS the free O2 molecule, step 2, put that free O2 molecule and surface together but make sure the distance is long enough that there is no interaction between them. step 3, compare step 1 O2 2p orbital with the step 2 O2 2p orbital (the Fermi level of them is shifted to zero). I expected the figure should be the same (completely o), but they are different. The whole figure is translated on the x axis. It is like two functions, when y > 0, y=x and y=x-2. The figures of the two functions is the same, but they are different in the axis. Although as Postnikov said that the fermi level has much useful meaning, when we shift the Fermi level to zero, we usually take "E-E_F" as x axis (E is energies for which DOS is calculated, E_F is Fermi energy ). If the case that I met exists , we cannot just choose "E-E_F" as x axis, so how can we shift the PDOS correctly ? Thank you very much again
