Non-selfconsistent calculation with arbitrary charge density
Posted: Thu Feb 11, 2010 10:11 am
Dear forum,
I have a question concerning calculations using ICHARG=11. I want to estimate the influence of charge rearrangements upon putting two fragments together on the final DOS of the combined system. For that purpose, I performed
- a self-consistent calculation on the full system
- a non-selfconsistent calculation on the full system (ICHARG=11) using as input charge density the sum of the charge densities of the individual fragments to be combined, leaving the augmentation occupancies unchanged.
From comparing the resulting DOS I want to conclude that
- the charge rearrangements are irrelevant for the resulting DOS as long as the scf and non-scf DOS match very well
or
- the charge rearrangements are relevant for the resulting DOS as long as the scf and non-scf DOS don't match.
I am asking if this interpretation is correct since I am not quite sure about the details of ICHARG=11. I tend to think that the input charge density is used to generate the potential/Hamiltonian and then the eigenvalues and functions are determined, but no updating of the charge density is done. If, however, the output density would be calculated, it could easily differ from the input density in my case. If input and output density differ sufficiently, the DOS (the eigenvalues), I guess, neither corresponds to input nor output density but is meaningless since self-consistency is not established. If the DOS doesn't match the scf-DOS this is, obviously, the case. The other way round I want to conclude that if the DOS equals the scf-DOS the differences between input and output density are, at least regarding the DOS, irrelevant.
Let me sum up my questions:
1) Can I draw the conclusion concerning the importance of charge rearrangements for the DOS using this kind of calculation?
2) Is there any way of interpreting the eigenvalues/the DOS when self-consistency (input equals output density) is NOT given?
Thanks for any help,
Ferdinand
I have a question concerning calculations using ICHARG=11. I want to estimate the influence of charge rearrangements upon putting two fragments together on the final DOS of the combined system. For that purpose, I performed
- a self-consistent calculation on the full system
- a non-selfconsistent calculation on the full system (ICHARG=11) using as input charge density the sum of the charge densities of the individual fragments to be combined, leaving the augmentation occupancies unchanged.
From comparing the resulting DOS I want to conclude that
- the charge rearrangements are irrelevant for the resulting DOS as long as the scf and non-scf DOS match very well
or
- the charge rearrangements are relevant for the resulting DOS as long as the scf and non-scf DOS don't match.
I am asking if this interpretation is correct since I am not quite sure about the details of ICHARG=11. I tend to think that the input charge density is used to generate the potential/Hamiltonian and then the eigenvalues and functions are determined, but no updating of the charge density is done. If, however, the output density would be calculated, it could easily differ from the input density in my case. If input and output density differ sufficiently, the DOS (the eigenvalues), I guess, neither corresponds to input nor output density but is meaningless since self-consistency is not established. If the DOS doesn't match the scf-DOS this is, obviously, the case. The other way round I want to conclude that if the DOS equals the scf-DOS the differences between input and output density are, at least regarding the DOS, irrelevant.
Let me sum up my questions:
1) Can I draw the conclusion concerning the importance of charge rearrangements for the DOS using this kind of calculation?
2) Is there any way of interpreting the eigenvalues/the DOS when self-consistency (input equals output density) is NOT given?
Thanks for any help,
Ferdinand