Dear Admin and VASP users,
I am trying to interpret the onecenter terms in CHGCAR.
These terms should represent Eq.7 of PhysRevB 59, 1758:
rho_ij = sum_n f_n <psi_np_i> <p_jpsi_n>
Thus, for element with a total of n lmdecomposed projectors, there should be n(n+1)/2 entries.
However, this is not the case.
For elements with 2s + 2p projectors such as O, n = 2*1 + 2*3 = 8, so I am expecting 8*9/2 = 36 entries while there are only 33 in CHGCAR.
Likely, for elements with 2s + 2p + 1d (such as Mg) or 2s + 2p + 2d (such as Zn), I am expecting 13*14/2 = 91 and 18*19/2 = 171 entries instead of 78 and 138 in CHGCAR, respectively.
The same also goes to augmentation part in POT file.
I am wondering what I am missing. Any help is appreciated.
Best regards,
YZ
Number of PAW onecenter entries in CHGCAR
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Re: Number of PAW onecenter entries in CHGCAR
Dear Younsheng,
If you would like to understand how the number of augmentation occupanices is calculated you should look at the routine RETRIEVE_RHOLM in paw_base.F
In the essence, we have two projectors for each angular momentum that gives us 2*n*(2*n'+1)/2. Then for each pair of angular momenta l and l' we add all occupancy channels J=2L+1, where L=ll'...l+l'.
And certain elements of this array will be zero due to the sum rule.
If you would like to understand how the number of augmentation occupanices is calculated you should look at the routine RETRIEVE_RHOLM in paw_base.F
In the essence, we have two projectors for each angular momentum that gives us 2*n*(2*n'+1)/2. Then for each pair of angular momenta l and l' we add all occupancy channels J=2L+1, where L=ll'...l+l'.
And certain elements of this array will be zero due to the sum rule.

 Newbie
 Posts: 2
 Joined: Mon Oct 16, 2023 8:02 am
Re: Number of PAW onecenter entries in CHGCAR
Dear Alexey
Thank you for your reply.
Now I have managed to understand the numbers.
They are stored using LM basis instead of ll'mm', and the terms that are identically zero are not written out.
Best regards,
YZ
Thank you for your reply.
Now I have managed to understand the numbers.
They are stored using LM basis instead of ll'mm', and the terms that are identically zero are not written out.
Best regards,
YZ