Re: [Ifeffit] [Ext] Meaning of ldosNN

[jaskirat brar]

Dear Alexey,

Thank you for your comments.

However, I still have a doubt.

The ldos01.dat and ldos02.dat both correspond to Ni atoms, but the DOS
looks different. I can not understand why it is so.
Could you comment on this, or maybe suggest some references that can help
me understand this.

Thanks and regards,
Jaskirat

On Wed, Feb 28, 2024 at 2:04 AM Jeffrey Terry  wrote:

> Now I don’t remember which one it is(was). I thought there was a separate
> file for each projection. In a few minutes I’ll go run a calculation and
> double check. Should have done that first instead of relying on memory.
> JeffSent from my iPhoneOn
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> Now I don’t remember which one it is(was).
>
> I thought there was a separate file for each projection. In a few minutes
> I’ll go run a calculation and double check. Should have done that first
> instead of relying on memory.
>
> Jeff
>
> Sent from my iPhone
>
> On Feb 27, 2024, at 1:58 PM, alexeyboubnov 
> wrote:
>
> 
> Hi Jeff, If i recall it correctly, ldosNN correspond to the unique
> potentials NN, with the relevant orbitals within each file. Just noticed
> that you replied in a different way, which might be confusing. Best
> regards, Alexey Sent from my T-Mobile
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> Hi Jeff,
>
> If i recall it correctly, ldosNN correspond to the unique potentials NN,
> with the relevant orbitals within each file.
>
> Just noticed that you replied in a different way,  which might be
> confusing.
>
> Best regards,
> Alexey
>
>
>
> Sent from my T-Mobile 4G LTE Device
>
>  Original message 
> From: Jeffrey Terry 
> Date: 2/27/24 19:18 (GMT+01:00)
> To: XAFS Analysis using Ifeffit 
> Subject: Re: [Ifeffit] [Ext]  Meaning of ldosNN
>
> Hi Jaskirat,
>
> Those are the s (l=0), p (l=1), and d (l=2) projected local density of
> states calculated using the potentials and atom geometries that you put in
> your model within the distance range that you told it to use when you set
> up the calculation.
>
> Jeff
>
>
> Sent from my iPhone
>
> On Feb 27, 2024, at 12:05 PM, jaskirat brar  wrote:
>
> 
> Dear list I have a question regarding DOS calculations using feff. (I am
> using feff8. 2) I have calculated the DOS of V-doped Ni, with Ni as the
> central atom and Ni and V as neighboring atoms. The potential indexes are 0
> - Ni 1 - Ni 2 - VI have
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> Dear list
>
> I have a question regarding DOS calculations using feff. (I am using
> feff8.2)
> I have calculated the DOS of V-doped Ni, with Ni as the central atom and
> Ni and V as neighboring atoms. The potential indexes are
> 0 - Ni
> 1 - Ni
> 2 - V
> I have obtained ldos00.dat, ldos01.dat, and ldos02.dat files corresponding
> to the l-projected DOS for the NNth potential index.
> I am not clear about the meaning of ldosNN.
> Does it correspond to the DOS of the central atom modified by the presence
> of the potential index NN? If yes, does ldos02 contain the effect of both
> potentials 01 and 02 or that of just 02?
> If this is not the case, what does ldosNN mean?
>
> Kindly provide your comments to clarify this.
>
> Thanks in advance.
>
> Jaskirat Brar
> FMP Lab, South Campus
> IIT Mandi, H.P., India
>
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Re: [Ifeffit] [IFEFFIT] Polarized FEFF calculation

[Matt Newville]

Hi Soyoung,


On Tue, Feb 27, 2024 at 6:50 PM Soyoung Kim  wrote:

> Dear Matthew, Thank you so much for your input. I followed your advice,
> and indeed the ratios of integrated chi(k) values between the polarized and
> isotropic cases matched reasonably well with the 3*cos^2(θ) values I
> calculated. To be exact,
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> Dear Matthew,
>
> Thank you so much for your input. I followed your advice, and indeed the
> ratios of integrated chi(k) values between the polarized and isotropic
> cases matched reasonably well with the 3*cos^2(θ) values I calculated. To
> be exact, I integrated the scattering amplitude f(k) (i.e., the mag[feff]
> column in the path file) and took their ratios.
>

That seems reasonable to me.


> In the process, I noticed that the f(k) is slightly different for the same
> kind of paths. For example, there are two Ru-Ru single scattering paths at
> 3.10 and 3.54 angstroms, and below is the f(k) of the two paths (from a
> non-polarized FEFF calculation):
> [image: image.png]
> Is this discrepancy just an artifact of the FEFF calculation?
>

I think that is pretty close, but I don't know for sure what the
differences there are.  I guess those are not from the same Feff run, so
there might be some subtle differences in potentials or path details.
Posting more details of what you did (inputs, feff.dat files) would
probably clarify that


While I'm not worried about such a small discrepancy for my project, this
> makes me wonder how exactly the FEFF calculates the effective scattering
> amplitudes and phases. While I will try to digest the FEFF user guide more,
> if you have any quick words of advice, I would appreciate it.
>

Well, Feff is calculating the intensity of the scattering by the
near-neighbor atoms by the photo-electron originating from the Ru
absorber.  Electron-electron scattering is "a little complicated"  ;).
There are a few good books and a few good review articles on this.  The
tutorial information at
https://urldefense.us/v3/__https://xafs.xrayabsorption.org/tutorials.html__;!!G_uCfscf7eWS!bp762sgHZFb8s_X_nBC2QIvU2vbLrwwQ3V_Q-kmkDrnBTh1_dEUigCCBOfWzwQOITapKqFxLDaSgKD0lJnfnjC9raF_9HcgeybjOncw$
  might be a good starting
point.

--Matt



> Thank you very much,
> Soyoung
>
>
> On Mon, Feb 19, 2024 at 12:28 PM Matthew Newville <
> newvi...@cars.uchicago.edu> wrote:
>
>> Hi Soyoung, I would not place too much importance to the value of the
>> "Importance" factor ;) That is, it is a quick estimate of the importance of
>> a Path so that it might be filtered out. As you'll notice, the first path
>> always has
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>> Hi Soyoung,
>>
>> I would not place too much importance to the value of the "Importance"
>> factor ;)That is, it is a quick estimate of the importance of a Path so
>> that it might be filtered out.As you'll notice, the first path always
>> has an Importance factor of 100, making comparisons between calculations
>> difficult.
>>
>> If you want to check how the scattering amplitude varies with angle, say
>> to check how close it is to cosine-squared, I recommend reading in the Path
>> files and integrating the magnitude of chi(k).
>>
>>
>>
>> --
>> *From:* Ifeffit  on behalf of
>> Soyoung Kim 
>> *Sent:* Thursday, February 15, 2024 3:01 PM
>> *To:* XAFS Analysis using Ifeffit 
>> *Subject:* [Ifeffit] [IFEFFIT] Polarized FEFF calculation
>>
>> This Message Is From an External Sender
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>>
>> Dear XAFS community,
>>
>> I have a series of Ru K-edge data on a single-crystal RuO2 sample
>> measured at different incident X-ray angles. Because of the linear
>> polarization of X-rays, the EXAFS of this single-crystal sample depends on
>> the X-ray angle. I am trying to fit the four EXAFS spectra simultaneously
>> with one set of parameters to extract the deltaR and MSRD parameters of
>> this sample.
>>
>> For oriented samples, N for a certain single scattering path is supposed
>> to be proportional to 3*cos^2(θ), where θ is the angle btwn the X-ray's
>> e-vector and the absorber-scatterer vector. Instead of manually calculating
>> the 3cos^2(θ) for all of the scattering paths in RuO2 (there are 7 single
>> and 3 multiple scattering paths that need to be included to achieve a good
>> fit with a reference RuO2 powder sample), I decided to use the polarization
>> card in my FEFF input. For example, for one of the X-ray angles, the
>> e-field vector would be (1, 0, 0), so I added the line "POLARIZATION 1 0 0"
>> in the FEFF input file.
>>
>> Running this input file gave me a list of paths that had different
>> importance values for each path compared to the non-polarized (isotropic)
>> calculation. *Sinc