DOS calculation - which ALGO

[fiori]

Hi all.
I have a probably naive question, but I am really puzzled and I cannot find a clear (at least for me) answer neither in the forum neither in the vasp documentation.

Problem: calculation of the Density of States and the selection of the proper algorithm (ALGO flag).

Commonly after a Self Consistent calculations (converged over the k-point mesh) (ALGO=N or Conjugate) I calculate the DOS within a NON Self Consistent calculation increasing the K point sampling and number of empty bands imposing the code read the pre-converged charge density (ICHARG=11).

From the vasp documentation for a DOS run ICHARG=11 is set and ALGO is not specified so by default it takes ALGO = N and NELMIN = 2.
Thus the calculation will do at least a 2 step SCF run, by reading the pre-converged charge density and recalculating the occupations and the eigenvalues for the new mesh of k points imposed.

To me this procedure is NOT equivalent to a NON-Self Consistent calculation normally used to calculate the DOS ....am I wrong?
Normally I just take the DOS calculated after a SCF calculation with a dense k-point mesh..but in the present case the size of my system does not me allow this trick.

Should I better use for example another ALGO like ALGO= Eigenval?
At the moment I am doing some cross-check runs, but if someone has the answer ready I will really appreciate a clarification.

Thanks a lot.
Federico Iori

[admin]

The parameter ALGO defines the minimisation algorithm.
Correctly converged electronic state does not depend on the numerical procedure
used to calculate the converged state. Therefore it is not strictly defined
which ALGO should be used.