I am trying to calculate PDOS for 3d transtion metallic systems and FeRh alloy. I have questions concerning total no of 3d electrons obtained from PDOS files:
1: Does/can Elk calculate total 3d electrons self-consistently( with LSDA/GGA) or is it just based on occupancy ,we put in, in species files?
2: If it is just based on occupancy we put in, how can we set it to correct numbers or numbers I want. Assume I want to set "6.49" 3 d electrons for Fe atoms, how should I change the occupancy of 3s, 3p , 3d and 4s orbitals? If there is any related reference, you could give, it would be really helpful.
3: Apart from changing occupancy of orbitals, do I need to change anything else in species or elk.in file related to setting up desired 3d electrons? like Nuclear charge? Metallic system is assumed to be pure/undoped/neutral.
From the calculation with standard Fe.in file, I am getting ~"6" 3d electrons from PDOS files whereas I want to have "6.49" 3d electrons in Fe.
Thannks and Regards
Naman
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From what I know, electrons in species files are the initial occupations.
The final occupations are found self-consistently.
Why would you define those from the start?
For question 2, please refer to this topic and the manual.
Next, atomic PDOS is actually a muffin-tin PDOS. I am almost sure that Fe 3d orbitals will be spatially larger than the muffin-tin sphere, and thus some portion of them will sit in the interstitial.
You might try estimating the "total" occupancy from TDOS. Say, Fe d PDOS peaks integrate to ~6, but the TDOS peak at the same energy (composed mostly of, say, Fe d and interstitial DOS/IDOS) inegrate to something else - that should be it.
Also, I'd like to know how exactly do you get the 6 from PDOS.
If you want to find the exact occupancy, I'd say you'd have to:
1. identify Fe 3d eigenvalues
2. calculate wavefunction plots for each of them
3. integrate each of them at proximity of Fe (i.e. by setting some lower threshold at which the "Fe 3d density" ends)
4. sum the integrated values and multiply by 2 (the wavefuction plots integrate to 1 electron per cell)
Best regards.
Andrew
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The final occupations are found self-consistently.
Why would you define those from the start?
If they are found self-consistently, then I don't need to.
Next, atomic PDOS is actually a muffin-tin PDOS. I am almost sure that Fe 3d orbitals will be >>spatially larger than the muffin-tin sphere, and thus some portion of them will sit in the >>interstitial.
If I interpret this correctly, the occupancy calculated from spin polarized PDOS will not be accurate as this is just Muffin -Tin PDOS ?
Would that also mean this spin polarized PDOS can't be used to calculate correct spin or orbital magnetic moments using sum rules?
Also, I'd like to know how exactly do you get the 6 from PDOS.
I calculate the no of electrons by integrating over spin polarized density of states of each atom which gives ~6.05 for per atom of iron.
Further I have follwoing questions:
1: If atomic PDOS are only muffin-tinPDOS , can they really be used to calculate correct 2p-3d individual sublevel XAS transitions, spin and orbital magnetic moments and sum rules? or do we need to use interstitial DOS or some thing else?
If you want to find the exact occupancy, I'd say you'd have to:
Why occupancy from PDOS, IDOS or TDOS are not accurate one?
identify Fe 3d eigenvalues:
Are these values the ones written in EIGVAL.OUT for each k?
calculate wavefunction plots for each of them
Are these calculated from task 135?
Regards
Naman
Last edit: NAMAN AGARWAL 2020-06-28
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Since PDOS does not contain delocalized part so we would need to take into account of IDOS also while calculating 2p-3d transitions. But task 10 only gives spin polarized IDOS which are not summed over l and m that means I can't separate s, p and d orbital character. So is there any way to get (l,m) resolved IDOS so that I can only get d orbitals contributing to total DOS by summing PDOS and IDOS?
Regards
Naman
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what you are asking for is not possible. You need to be aware that in a solid, there is no clean way of defining s,p,d,f,... angular momenta for the atoms because angular momentum is not a conserved quantity (instead, linear momentum is!). What people typically do is to project the self-consistent wavefunctions obtained with a sufficiently complete basis onto the orbitals of the corresponding free atoms. Or, what you can do in elk, is to simply look at the projections onto the angular momentum characters of the APW+lo+LO basis set itself. However, an angular-momentum-aware basis set is only used in the muffin-tins. Outside, planewaves are used, thus there is no direct way of looking at the angular momentum projections there and you are always missing some charge by just looking at the PDOS.
I remember there is a way using a basin evaluation of the angular momentum projections where atoms are defined by some property of the charge density. Have a look at Alexey Baranov's dGrid 4.6 program. However, I doubt it will work with the present version of elk.
When looking at optical 2p-3d transitions, you can also do these with task 121. Just put in local orbitals for your 2p states and move them from core to valence and switch on spinorb. Similarly you can calculate EELS.
Best wishes,
Markus
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Dear all,
I am trying to calculate PDOS for 3d transtion metallic systems and FeRh alloy. I have questions concerning total no of 3d electrons obtained from PDOS files:
1: Does/can Elk calculate total 3d electrons self-consistently( with LSDA/GGA) or is it just based on occupancy ,we put in, in species files?
2: If it is just based on occupancy we put in, how can we set it to correct numbers or numbers I want. Assume I want to set "6.49" 3 d electrons for Fe atoms, how should I change the occupancy of 3s, 3p , 3d and 4s orbitals? If there is any related reference, you could give, it would be really helpful.
3: Apart from changing occupancy of orbitals, do I need to change anything else in species or elk.in file related to setting up desired 3d electrons? like Nuclear charge? Metallic system is assumed to be pure/undoped/neutral.
From the calculation with standard Fe.in file, I am getting ~"6" 3d electrons from PDOS files whereas I want to have "6.49" 3d electrons in Fe.
Thannks and Regards
Naman
Dear Naman,
From what I know, electrons in species files are the initial occupations.
The final occupations are found self-consistently.
Why would you define those from the start?
For question 2, please refer to this topic and the manual.
Next, atomic PDOS is actually a muffin-tin PDOS. I am almost sure that Fe 3d orbitals will be spatially larger than the muffin-tin sphere, and thus some portion of them will sit in the interstitial.
You might try estimating the "total" occupancy from TDOS. Say, Fe d PDOS peaks integrate to ~6, but the TDOS peak at the same energy (composed mostly of, say, Fe d and interstitial DOS/IDOS) inegrate to something else - that should be it.
Also, I'd like to know how exactly do you get the 6 from PDOS.
If you want to find the exact occupancy, I'd say you'd have to:
1. identify Fe 3d eigenvalues
2. calculate wavefunction plots for each of them
3. integrate each of them at proximity of Fe (i.e. by setting some lower threshold at which the "Fe 3d density" ends)
4. sum the integrated values and multiply by 2 (the wavefuction plots integrate to 1 electron per cell)
Best regards.
Andrew
Dear Andrew,
Thanks for the reply.
If they are found self-consistently, then I don't need to.
If I interpret this correctly, the occupancy calculated from spin polarized PDOS will not be accurate as this is just Muffin -Tin PDOS ?
Would that also mean this spin polarized PDOS can't be used to calculate correct spin or orbital magnetic moments using sum rules?
I calculate the no of electrons by integrating over spin polarized density of states of each atom which gives ~6.05 for per atom of iron.
Further I have follwoing questions:
1: If atomic PDOS are only muffin-tinPDOS , can they really be used to calculate correct 2p-3d individual sublevel XAS transitions, spin and orbital magnetic moments and sum rules? or do we need to use interstitial DOS or some thing else?
Why occupancy from PDOS, IDOS or TDOS are not accurate one?
Are these values the ones written in EIGVAL.OUT for each k?
Are these calculated from task 135?
Regards
Naman
Last edit: NAMAN AGARWAL 2020-06-28
Dear Andrew,
I have another question.
Since PDOS does not contain delocalized part so we would need to take into account of IDOS also while calculating 2p-3d transitions. But task 10 only gives spin polarized IDOS which are not summed over l and m that means I can't separate s, p and d orbital character. So is there any way to get (l,m) resolved IDOS so that I can only get d orbitals contributing to total DOS by summing PDOS and IDOS?
Regards
Naman
Dear Naman,
what you are asking for is not possible. You need to be aware that in a solid, there is no clean way of defining s,p,d,f,... angular momenta for the atoms because angular momentum is not a conserved quantity (instead, linear momentum is!). What people typically do is to project the self-consistent wavefunctions obtained with a sufficiently complete basis onto the orbitals of the corresponding free atoms. Or, what you can do in elk, is to simply look at the projections onto the angular momentum characters of the APW+lo+LO basis set itself. However, an angular-momentum-aware basis set is only used in the muffin-tins. Outside, planewaves are used, thus there is no direct way of looking at the angular momentum projections there and you are always missing some charge by just looking at the PDOS.
I remember there is a way using a basin evaluation of the angular momentum projections where atoms are defined by some property of the charge density. Have a look at Alexey Baranov's dGrid 4.6 program. However, I doubt it will work with the present version of elk.
When looking at optical 2p-3d transitions, you can also do these with task 121. Just put in local orbitals for your 2p states and move them from core to valence and switch on spinorb. Similarly you can calculate EELS.
Best wishes,
Markus