[Pw_forum] xspectra calculation error

[sreekar guddeti]

>
>
> Dear all,

Respected Mr. Ibrahim,

>
> ?? I am trying to run xspectra calculation on MgSe. Knowing that there is
> no gipaw pseudopotential for both contributing element on
> ? the pwscf-pseudo page, i tried to generate one for both Mg and Se. After
> running scf with this pseudo, i proceed to running the
> ? xspectra with xspectra.x but to my surprise, it keeps given this error ;
>
> ? ?? from allocate_fft : error # 1
>  the nr"s are too small!
> Please, can anybody help me out with this?
>
>
A helpful tool(weapon :D) for tracking down errors is to use (learnt from
Prof. Gianozzi's replies on the forum)
$ grep -e '' */*.f90

In this case,,
$ grep -e 'are too small' */*.f90

Results gives  the relevant code file where it occurs.

$PW/allocate_fft.f90: CALL errore ('allocate_fft', 'the nr"s are too
small!', 1)
$PW/allocate_fft.f90: CALL errore ('allocate_fft', 'the nrs"s are too
small!', 1)

A look at the file PW/allocate_fft.f90 suggests that
-
  IF (nrxx.lt.ngm) THEN
 WRITE( stdout, '(/,4x," nr1=",i4," nr2= ", i4, " nr3=",i4, &
  &" nrxx = ",i8," ngm=",i8)') nr1, nr2, nr3, nrxx, ngm
 CALL errore ('allocate_fft', 'the nr"s are too small!', 1)
-

Here
nrxx = nr1*nr2*nr3 (Modules/griddim.f90), the minimal 3D real-space FFT
grid required to fit the G-vector sphere with G^2 <= gcut
ngm = local  number of G vectors (Modules/recvec.f90).

I have not generated PPs, but I can only infer that your FFT grid density is
not sufficient enough to accommodate the G-vectors.

Sincerely,

--
Sreekar Guddeti
Undergraduate (5th year)
Engineering Physics
IIT Bombay
India
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[Pw_forum] XSpectra calculation error

[Matteo Calandra]

>
> Message: 3
> Date: Sun, 4 Sep 2011 21:58:18 -0700 (PDT)
> From: bamidele ibrahim
> Subject: [Pw_forum] xspectra calculation error
> To: PWSCF Forum
> Message-ID:
>   <1315198698.76736.YahooMailNeo at web39408.mail.mud.yahoo.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear all,
>
> ?? I am trying to run xspectra calculation on MgSe. Knowing that there is no 
> gipaw pseudopotential for both contributing element on
> ? the pwscf-pseudo page, i tried to generate one for both Mg and Se. After 
> running scf with this pseudo, i proceed to running the
> ? xspectra with xspectra.x but to my surprise, it keeps given this error ;
>
> ? ?? from allocate_fft : error # 1
>  the nr"s are too small!
> Please, can anybody help me out with this?
>
> ?


Dear Adetunji,

   which version of the code are you using ?
Can you first try to run the examples to see that this is not
related in some way to your input files or other.
Maybe you can send us the input/output files to better
understand what are you doing.

All the best, M.


> Adetunji Bamidele Ibrahim
> Department of physics,University of Agriculture,
> Abeokuta, Ogun State,Nigeria.
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>
> --
>
> Message: 4
> Date: Mon, 05 Sep 2011 02:51:22 -0400
> From: vkarthik
> Subject: [Pw_forum] Segmentation fault with pp.x
> To: pw_forum at pwscf.org
> Message-ID:<20110905025122.589gwx9kbo00ckok at webmail.mit.edu>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Hi,
>
> I am using quantum espresso-4.3.2 and running some examples given at the
> tutorial website on the quantum espresso
> webpage.http://www.fisica.uniud.it/~giannozz/QE-Tutorial/ PWscf - Simple
> examples
>
> I am trying to run a post process job to determine the charge density.
> As mentioned in the slides when I run the command
> prompt>  espresso_dir/bin/pp.x<  si.pp_rho.in
> I get en error message
> Program POST-PROC v.4.3.2  starts on  5Sep2011 at 12:13:38
>
>   This program is part of the open-source Quantum ESPRESSO suite
>   for quantum simulation of materials; please cite
>   "P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
>URL http://www.quantum-espresso.org;,
>   in publications or presentations arising from this work. More details at
>   http://www.quantum-espresso.org/wiki/index.php/Citing_Quantum-ESPRESSO
>
> Info: using nr1, nr2, nr3 values from input
>
> Info: using nr1s, nr2s, nr3s values from input
>
>   G-vector sticks info
>   
>   sticks:   dense  smooth PW G-vecs:dense   smooth  PW
>   Sum 163 163 61 1459 1459 339
>
> Segmentation fault
>
> any help would be appreciated.
> best,
> Karthik
>
>
>
> --
>
> Message: 5
> Date: Mon, 5 Sep 2011 09:03:43 +0200
> From: Changru Ma
> Subject: Re: [Pw_forum] Segmentation fault with pp.x
> To: PWSCF Forum
> Message-ID:
> Content-Type: text/plain; charset="us-ascii"
>
> Dear Karthik,
>
> It's explained in the User Guide.
>
> 12.6.0.1 Why is my job crashing with ``segmentation fault''?
>
> Possible reasons: too much memory requested; executable or libraries fitted 
> to a different hardware; code bug; compiler bug. The latter are typically not 
> reproducible on different architectures or compilers; code bugs may sometimes 
> be elusive, but typically yield a more reproducible, pattern of problems.
>
> Mysterious, unpredictable, erratic errors in parallel execution are almost 
> always coming from bugs in the compiler or/and in the MPI libraries and 
> sometimes even from flaky hardware. Sorry, not our fault.
>
> HTH,
> Changru
>
> On 5 Sep, 2011, at 08:51, vkarthik wrote:
>
>> Hi,
>>
>> I am using quantum espresso-4.3.2 and running some examples given at the
>> tutorial website on the quantum espresso
>> webpage.http://www.fisica.uniud.it/~giannozz/QE-Tutorial/ PWscf - Simple
>> examples
>>
>> I am trying to run a post process job to determine the charge density.
>> As mentioned in the slides when I run the command
>> prompt>  espresso_dir/bin/pp.x<  si.pp_rho.in
>> I get en error message
>> Program POST-PROC v.4.3.2  starts on  5Sep2011 at 12:13:38
>>
>>  This program is part of the open-source Quantum ESPRESSO suite
>>  for quant

[Pw_forum] xspectra calculation error

[bamidele ibrahim]

Dear all,

?? I am trying to run xspectra calculation on MgSe. Knowing that there is no 
gipaw pseudopotential for both contributing element on
? the pwscf-pseudo page, i tried to generate one for both Mg and Se. After 
running scf with this pseudo, i proceed to running the
? xspectra with xspectra.x but to my surprise, it keeps given this error ;

? ?? from allocate_fft : error # 1
 the nr"s are too small!
Please, can anybody help me out with this?

?
Adetunji Bamidele Ibrahim
Department of physics,University of Agriculture,
Abeokuta, Ogun State,Nigeria.
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[Pw_forum] xspectra calculation

[wumindt2]

Dear Matteo,

When i cut the occupied state  with "cut_occ_states=.true.", there is a small 
peak appeared at the energy of ef_r i set.
In the element of "cut_occ", only cut_desmooth = 0.01 was set. The others
are using default value. 
So what's the reason of this small peak? 
How to cut the occupied states smoothly?
Thanks.

With Regards,

Min Wu
2010-10-23

[Pw_forum] xspectra calculation

[jiayudai]

Dear Matteo,

Do you think what's the difference between the method in XSpectra code and the 
method in Abinit (see the ref: 
http://prl.aps.org/abstract/PRL/v101/i15/e155001, 
http://prb.aps.org/abstract/PRB/v80/i6/e064110). I think the treatment is very 
similar, but they consider the Fermi-Dirac distribution for electrons. It seems 
that they also cut the occupied states when they calculate the xanes. So, do 
you think if we consider the Fermi distribution of electrons, this model can be 
used for metals?

Regards.

Jiayu

--

Message: 5
Date: Wed, 20 Oct 2010 17:13:39 +0200
From: Matteo Calandra 
Subject: Re: [Pw_forum] xspectra calculation
To: pw_forum at pwscf.org
Message-ID: <4CBF0723.9030508 at impmc.jussieu.fr>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

>Dear Matteo,

>So when we just do the dipolar part, we don't need to care about the
>k vector, right?

yes, it is not used.

>Besides, in order to compare with an experimental spectrum, is it necessary to 
>cut
>the occupied state below Fermi energy level within our Xspectra calculation ?
>In that case, we should set "cut_occ_states" = .true. and 
>"ef_r" equal to the fermi energy we got in the scf calculation. Is it?

Yes. However if you have a small gap insulator, introduction of a 
core-hole can lead to a metallic system (close the gap). In this case it is
not clear where to cut. Actually in this case the static core-hole 
approximation is probably incorrect.
For metals it is even worst.

M.

Best regards,

[Pw_forum] xspectra calculation

[Matteo Calandra]

Dear Jiayu

 >And i think even for dipolar part, the direction of k vector should be 
 >important in some cases, such as the SiO2 in the example.

No, this is incorrect. The dipolar part cross section does not depend
on k.

 >And if we
 >want to compare the results with some experiments, we should cut the 
 >contribution of occupied states, that is, cut_occ_states = .true. 
 >should be used. But we should shift the position by hand in order to 
 >compare the results, cause i think it is very difficult to get the 
 >accurate position in DFT, or even in atomic physics, it is a difficult 
 >problem to determine the position of spectra. The "ef_r" should be the 
 >fermi energy in scf calculation with core-hole, i think.

On this second point you are right in the method but not on the reason
why one should cut at somewhat lower values with respect to e_f.
The problems that you can face are the following:

1) You have a system with a gap even in the presence of a core-hole
. In this case if you cut exactly at the bottom of the conduction band 
(empty states) then the cut_occ_states procecure can miss this peak.
So it is safer to cut at somewhat lower energy than the bottom of the
conduction band.

2) You have a system without gap in the presence of a core-hole
(either because it was a metal even without core-hole or because it
was a small gap semiconductor that becomes a metal when the core-hole
is inserted). In this case identification of where to cut is ill 
defined. In this case you should keep in mind that probably core hole
effects are not correctly described.
Of course, if DFT underestimates the gap you can easily end up in a 
metallic solution.

All the best, M.


Jiayu


-- 
* * * *
Matteo Calandra, Charge de Recherche (CR1)
Institut de Min?ralogie et de Physique des Milieux Condens?s de Paris
Universit? Pierre et Marie Curie, tour 16, case 115
4 Place Jussieu, 75252 Paris Cedex 05 France
Tel: +33-1-44 27 52 16   Fax: +33-1-44 27 37 85
http://www.impmc.jussieu.fr/~calandra

[Pw_forum] xspectra calculation

[jiayudai]

Dear Matteo and Min Wu,

Several daysa ago, i said a problem in my calculations with high pressure. With 
the help of Matteo, the problem has been solved, and that is because of my 
fault, where i misread the units of ef_r (in Ry here). Thank Matteo.

And i think even for dipolar part, the direction of k vector should be 
important in some cases, such as the SiO2 in the example. And if we want to 
compare the results with some experiments, we should cut the contribution of 
occupied states, that is, cut_occ_states = .true. should be used. But we should 
shift the position by hand in order to compare the results, cause i think it is 
very difficult to get the accurate position in DFT, or even in atomic physics, 
it is a difficult problem to determine the position of spectra. The "ef_r" 
should be the fermi energy in scf calculation with core-hole, i think.

Am i right?

Jiayu


--

Message: 3
Date: Wed, 20 Oct 2010 07:07:16 +0800
From: "wumindt2" 
Subject: Re: [Pw_forum] xspectra calculation
To: pw_forum at pwscf.org
Message-ID: 
Content-Type: text/plain; charset="gb2312"

Dear Matteo,

So when we just do the dipolar part, we don't need to care about the
k vector, right?

Besides, in order to compare with an experimental spectrum, is it necessary to 
cut
the occupied state below Fermi energy level within our Xspectra calculation ?
In that case, we should set "cut_occ_states" = .true. and 
"ef_r" equal to the fermi energy we got in the scf calculation. Is it?

Best regards,

Min Wu
2010-10


---
Jiayu Dai
Department of Physics
National University of Defense Technology, 
Changsha, 410073, P R China
-

[Pw_forum] xspectra calculation

[Matteo Calandra]

>Dear Matteo,

>So when we just do the dipolar part, we don't need to care about the
>k vector, right?

yes, it is not used.

>Besides, in order to  compare with an experimental spectrum, is it necessary 
>to cut
>the occupied state below Fermi energy level within our Xspectra calculation ?
>In that case, we should set "cut_occ_states" = .true. and 
>"ef_r" equal to the fermi energy we got in the scf calculation. Is it?

Yes. However if you have a small gap insulator, introduction of a 
core-hole can lead to a metallic system (close the gap). In this case it is
not clear where to cut. Actually in this case the static core-hole 
approximation is probably incorrect.
For metals it is even worst.

M.

Best regards,

Min Wu
2010-10


-- 
* * * *
Matteo Calandra, Charge de Recherche (CR1)
Institut de Min?ralogie et de Physique des Milieux Condens?s de Paris
Universit? Pierre et Marie Curie, tour 16, case 115
4 Place Jussieu, 75252 Paris Cedex 05 France
Tel: +33-1-44 27 52 16   Fax: +33-1-44 27 37 85
http://www.impmc.jussieu.fr/~calandra

[Pw_forum] xspectra calculation

[wumindt2]

Dear Matteo,

So when we just do the dipolar part, we don't need to care about the
k vector, right?

Besides, in order to  compare with an experimental spectrum, is it necessary to 
cut
the occupied state below Fermi energy level within our Xspectra calculation ?
In that case, we should set "cut_occ_states" = .true. and 
"ef_r" equal to the fermi energy we got in the scf calculation. Is it?

Best regards,

Min Wu
2010-10



>From: Matteo Calandra 
>Reply-To: PWSCF Forum 
>To: pw_forum at pwscf.org
>Subject: Re: [Pw_forum] xspectra calculation
>Date: Tue, 19 Oct 2010 16:28:30 +0200
>
>Dear Min Wu,
>
> >
> >It seems i have found the problem. It's not the problem of the
> >xcoordcrys. I set it as .true. and the polarization vectors are 
>(0,0,1) >and
> >(0,1,0). The xray k vector is the default value (1,0,0).
> >BTW, can we use the same vector for polarization and xay k moment?
> >e.g. Both of them are (1,0,0). Is it OK?
>
>Of course epsilon and k MUST be ortogonal otherwise what you are doing
>is meaningless. If you calculate the dipolar part only then
>the k-vector is not used and can take any value.
>
> >
> >The problem i found is that i set the "cut_occ_states" = .true.
> >Then it cut all the occupied state that i expected to see.
> >When i reset it to .false., i saw the expected peak.
> >
>
>Maybe your ef_r is not in the correct units... Of course you put the
>Fermi level in the presence of a core-hole, don't you ?
>
> >I have another problem, what does the "ef_r" do in the calculation?
> >For instance, i got fermi level of -5 eV with scf calculation.
> >The i set ef_r= -5/13.6 Ry. Then, in the calculated xspectra data, 
> >where is
> >the Fermi level? It is ajusted to 0 eV, or still is the -5 eV?
> >
>
>zero, the energies are simply shifted.
>
>M.
>
>-- 
>* * * *
>Matteo Calandra, Charge de Recherche (CR1)
>Institut de Min?ralogie et de Physique des Milieux Condens?s de Paris
>Universit? Pierre et Marie Curie, tour 16, case 115
>4 Place Jussieu, 75252 Paris Cedex 05 France
>Tel: +33-1-44 27 52 16   Fax: +33-1-44 27 37 85
>http://www.impmc.jussieu.fr/~calandra
>___
>Pw_forum mailing list
>Pw_forum at pwscf.org
>http://www.democritos.it/mailman/listinfo/pw_forum
> 

[Pw_forum] xspectra calculation

[Matteo Calandra]

Dear Min Wu,

 >
 >It seems i have found the problem. It's not the problem of the
 >xcoordcrys. I set it as .true. and the polarization vectors are 
(0,0,1) >and
 >(0,1,0). The xray k vector is the default value (1,0,0).
 >BTW, can we use the same vector for polarization and xay k moment?
 >e.g. Both of them are (1,0,0). Is it OK?

Of course epsilon and k MUST be ortogonal otherwise what you are doing
is meaningless. If you calculate the dipolar part only then
the k-vector is not used and can take any value.

 >
 >The problem i found is that i set the "cut_occ_states" = .true.
 >Then it cut all the occupied state that i expected to see.
 >When i reset it to .false., i saw the expected peak.
 >

Maybe your ef_r is not in the correct units... Of course you put the
Fermi level in the presence of a core-hole, don't you ?

 >I have another problem, what does the "ef_r" do in the calculation?
 >For instance, i got fermi level of -5 eV with scf calculation.
 >The i set ef_r= -5/13.6 Ry. Then, in the calculated xspectra data, 
 >where is
 >the Fermi level? It is ajusted to 0 eV, or still is the -5 eV?
 >

zero, the energies are simply shifted.

M.

-- 
* * * *
Matteo Calandra, Charge de Recherche (CR1)
Institut de Min?ralogie et de Physique des Milieux Condens?s de Paris
Universit? Pierre et Marie Curie, tour 16, case 115
4 Place Jussieu, 75252 Paris Cedex 05 France
Tel: +33-1-44 27 52 16   Fax: +33-1-44 27 37 85
http://www.impmc.jussieu.fr/~calandra

[Pw_forum] xspectra calculation (wumindt2)

[wumindt2]

Dear Matteo, 

It seems i have found the problem. It's not the problem of the 
xcoordcrys. I set it as .true. and the polarization vectors are (0,0,1) and
(0,1,0). The xray k vector is the default value (1,0,0).
BTW, can we use the same vector for polarization and xay k moment? 
e.g. Both of them are (1,0,0). Is it OK?

The problem i found is that i set the "cut_occ_states" = .true.
Then it cut all the occupied state that i expected to see.
When i reset it to .false., i saw the expected peak. 

I have another problem, what does the "ef_r" do in the calculation?
For instance, i got fermi level of -5 eV with scf calculation.
The i set ef_r= -5/13.6 Ry. Then, in the calculated xspectra data, where is
the Fermi level? It is ajusted to 0 eV, or still is the -5 eV?

Sorry to bother you again.
Thanks so much.

Cheers,

Min Wu 2010-10-18



>From: Matteo Calandra 
>Reply-To: PWSCF Forum 
>To: pw_forum at pwscf.org
>Subject: Re:[Pw_forum] xspectra calculation (wumindt2)
>Date: Mon, 18 Oct 2010 09:35:10 +0200
>
>dear Min Wu,
>
>  the attachment do not go through the pw_forum, so I cannot
>do much about it. What I can tell you is that we calculate
>Co and LiCoO2 and we get a good agreement with experiments.
>Maybe you can try to compare with the following paper:
>
>Juhin et al. Phys. Rev. B 81, 115115 (2010)
>http://link.aps.org/doi/10.1103/PhysRevB.81.115115
>
>Anyway, from four message what seems to be wrong (assuming the scf
>run to be correct) are the unit of the polarization vector
>(assuming you're dealing with the dipolar part only and assuming
>the peak you're referring to is dipolar). Did you set xcoordcrys to
>the proper value (see below)?
>
>For zhqt concerns CoO2, note that the pre-edge
>of CoO2 at the Co K-edge has a quadrupolar part, so if you stick
>to the dipolar calculation you want be able to reproduce the pre-edge 
>peak. Note also that in the case of LiCoO2, which is probably
>not so different from yours, DFT fails in the
>pre-edge and you have to use DFT+U.
>
>In particular, remember that if you don't set the variable
>xcoordcrys=.false. your xepsilon and xkvec are in reduced coordinates.
> From Doc/INPUT_XSPECTRA
>
>xkvec(1:3)real(DP) 
>DEFAULT=(1.0,0
>.0,0.0)
>   coordinates of the x-ray momentum k
>
>
>xepsilon(1:3) real(DP) 
>DEFAULT=(1.0,0
>.0,0.0)
>   coordinates of the incident x-ray
>   polarization vector
>
>xcoordcryslogical 
>DEFAULT=.true.
>   .true. to use crystal coordinates for
>   k and epsilon
>
>
>Maybe you could try to reproduce our calculation on LiCoO2 so that
>you are sure of not having any errors with the input file.
>The paper is very detailed so you can compare every step in the calculation.
>
>All the best, M.
>
> >Message: 6
> >Date: Mon, 18 Oct 2010 05:03:50 +0800
> >From: "wumindt2"

> >Subject: Re: [Pw_forum] Xspectra calculation (wumindt2)
> >To: pw_forum at pwscf.org
> >Message-ID:

> >Content-Type: text/plain; charset="gb2312"
>
> >Dear Matteo,
>
> >I met some problem when calculating the XASs with the Xspectra.
> >I tested the example of quartz, and got the consistent result with the
> >published work.
> >Then i moved on to test another example of solid CO2, which has an 
> >isotropic
> >symmetry according to C. Brouder's paper. But the X-ray absorption 
> >spectrum
> >i got was totally wrong. The first sharp peak which is well-known 
> >existing
> >in CO2 was not found.
> >We also tested a single CO2 molecule which is still a clear-cut >example.
> >The C atom and the two O atoms are all in the Z axis. So the 
> >polarization vectors
> >of (0,0,1) and (1,0,0) are enough for this case. However, we still 
> >cannot get the
> >right XAS. To make it easier for you to understand my problem, I 
> >attached the input files of this calculation.
> >The GIPAW pseudopotentials i used were downloaded from the website of >QE.
>
> >Thanks a lot for the help.
>
> >Best regards,
>
> >Min Wu
>___
>Pw_forum mailing list
>Pw_forum at pwscf.org
>http://www.democritos.it/mailman/listinfo/pw_forum
> 

[Pw_forum] xspectra calculation (wumindt2)

[Matteo Calandra]

dear Min Wu,

  the attachment do not go through the pw_forum, so I cannot
do much about it. What I can tell you is that we calculate
Co and LiCoO2 and we get a good agreement with experiments.
Maybe you can try to compare with the following paper:

Juhin et al. Phys. Rev. B 81, 115115 (2010)
http://link.aps.org/doi/10.1103/PhysRevB.81.115115

Anyway, from four message what seems to be wrong (assuming the scf
run to be correct) are the unit of the polarization vector
(assuming you're dealing with the dipolar part only and assuming
the peak you're referring to is dipolar). Did you set xcoordcrys to
the proper value (see below)?

For zhqt concerns CoO2, note that the pre-edge
of CoO2 at the Co K-edge has a quadrupolar part, so if you stick
to the dipolar calculation you want be able to reproduce the pre-edge 
peak. Note also that in the case of LiCoO2, which is probably
not so different from yours, DFT fails in the
pre-edge and you have to use DFT+U.

In particular, remember that if you don't set the variable
xcoordcrys=.false. your xepsilon and xkvec are in reduced coordinates.
 From Doc/INPUT_XSPECTRA

xkvec(1:3)real(DP) 
DEFAULT=(1.0,0
.0,0.0)
   coordinates of the x-ray momentum k


xepsilon(1:3) real(DP) 
DEFAULT=(1.0,0
.0,0.0)
   coordinates of the incident x-ray
   polarization vector

xcoordcryslogical 
DEFAULT=.true.
   .true. to use crystal coordinates for
   k and epsilon


Maybe you could try to reproduce our calculation on LiCoO2 so that
you are sure of not having any errors with the input file.
The paper is very detailed so you can compare every step in the calculation.

All the best, M.

 >Message: 6
 >Date: Mon, 18 Oct 2010 05:03:50 +0800
 >From: "wumindt2" 
 >Subject: Re: [Pw_forum] Xspectra calculation (wumindt2)
 >To: pw_forum at pwscf.org
 >Message-ID: 
 >Content-Type: text/plain; charset="gb2312"

 >Dear Matteo,

 >I met some problem when calculating the XASs with the Xspectra.
 >I tested the example of quartz, and got the consistent result with the
 >published work.
 >Then i moved on to test another example of solid CO2, which has an 
 >isotropic
 >symmetry according to C. Brouder's paper. But the X-ray absorption 
 >spectrum
 >i got was totally wrong. The first sharp peak which is well-known 
 >existing
 >in CO2 was not found.
 >We also tested a single CO2 molecule which is still a clear-cut >example.
 >The C atom and the two O atoms are all in the Z axis. So the 
 >polarization vectors
 >of (0,0,1) and (1,0,0) are enough for this case. However, we still 
 >cannot get the
 >right XAS. To make it easier for you to understand my problem, I 
 >attached the input files of this calculation.
 >The GIPAW pseudopotentials i used were downloaded from the website of >QE.

 >Thanks a lot for the help.

 >Best regards,

 >Min Wu

[Pw_forum] Xspectra calculation (wumindt2)

[wumindt2]

Dear Matteo,

I met some problem when calculating the XASs with the Xspectra.
I tested the example of quartz, and got the consistent result with the
published work.
Then i moved on to test another example of solid CO2, which has an isotropic
symmetry according to C. Brouder's paper. But the X-ray absorption spectrum
i got was totally wrong. The first sharp peak which is well-known existing
in CO2 was not found.
We also tested a single CO2 molecule which is still a clear-cut example.
The C atom and the two O atoms are all in the Z axis. So the polarization 
vectors 
of (0,0,1) and (1,0,0) are enough for this case. However, we still cannot get 
the
right XAS. To make it easier for you to understand my problem, I attached the 
input files of this calculation.
The GIPAW pseudopotentials i used were downloaded from the website of QE.
 
Thanks a lot for the help. 

Best regards,

Min Wu
2010-10-17


>From: Matteo Calandra 
>Reply-To: PWSCF Forum 
>To: pw_forum at pwscf.org
>Subject: Re: [Pw_forum] Xspectra calculation (wumindt2)
>Date: Mon, 11 Oct 2010 10:08:16 +0200
>
>Dear
>
>  I assume you are talking of the dipolar part only.
>For the quadrupolar it is substantially more complicate.
>The number of independent calculations that you have
>to perform to obtain the isotropic cross section (powder)
>depends on the  point group of the space group
>of your crystal.
>It is 1 for a cubic or tetraedric crystal,
>2 for a uniaxial crystal and it is 3, 4, 6 for a biaxial
>(ot trichroic) crystal.
>I suggest you read
>C. Brouder J. Phys.: Condens. Matter 2 (1990) 701-738
>for more details.
>
>M.
>
>
>> 
>> Message: 3
>> Date: Sat, 09 Oct 2010 22:48:53 +0800
>> From: "wumindt2"

>> Subject: Re: [Pw_forum] Xspectra calculation
>> To: pw_forum at pwscf.org
>> Message-ID:

>> Content-Type: text/plain;charset="gb2312"
>> 
>> Dear matteo,
>> 
>> Thanks. 
>> 
>> For dichroism compound, do we just need the in-plane and the c-axis
>> polarization vectors? 
>> While for trichroism compound, do we need to calculate three different
>> polarization vectors?
>> Am i right?
>> 
>> Best regards,
>> 
>___
>Pw_forum mailing list
>Pw_forum at pwscf.org
>http://www.democritos.it/mailman/listinfo/pw_forum
> 
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[Pw_forum] Xspectra calculation (wumindt2)

[wumindt2]

Dear Matteo,

Thanks for the information, i read the C. Brouder the paper a little bit.
I'am still not sure how to choose the polarization vector.
For instance, we have a crystal with spacegroup of P42/MNM, point group of 
4/mmm.
According to the Table in C. Brouder's paper, this is a dichroism compound.
Thus, how can we choose the polarization vector when calculating the XAS
of this compound?
Can you please show me how? 

Thanks so much!

Cheers,

Min Wu
2010-10-12


>From: Matteo Calandra 
>Reply-To: PWSCF Forum 
>To: pw_forum at pwscf.org
>Subject: Re: [Pw_forum] Xspectra calculation (wumindt2)
>Date: Mon, 11 Oct 2010 10:08:16 +0200
>
>Dear
>
>  I assume you are talking of the dipolar part only.
>For the quadrupolar it is substantially more complicate.
>The number of independent calculations that you have
>to perform to obtain the isotropic cross section (powder)
>depends on the  point group of the space group
>of your crystal.
>It is 1 for a cubic or tetraedric crystal,
>2 for a uniaxial crystal and it is 3, 4, 6 for a biaxial
>(ot trichroic) crystal.
>I suggest you read
>C. Brouder J. Phys.: Condens. Matter 2 (1990) 701-738
>for more details.
>
>M.
>
>
>> 
>> Message: 3
>> Date: Sat, 09 Oct 2010 22:48:53 +0800
>> From: "wumindt2"

>> Subject: Re: [Pw_forum] Xspectra calculation
>> To: pw_forum at pwscf.org
>> Message-ID:

>> Content-Type: text/plain;charset="gb2312"
>> 
>> Dear matteo,
>> 
>> Thanks. 
>> 
>> For dichroism compound, do we just need the in-plane and the c-axis
>> polarization vectors? 
>> While for trichroism compound, do we need to calculate three different
>> polarization vectors?
>> Am i right?
>> 
>> Best regards,
>> 
>___
>Pw_forum mailing list
>Pw_forum at pwscf.org
>http://www.democritos.it/mailman/listinfo/pw_forum
> 

[Pw_forum] Xspectra calculation (wumindt2)

[Matteo Calandra]

Dear

  I assume you are talking of the dipolar part only.
For the quadrupolar it is substantially more complicate.
The number of independent calculations that you have
to perform to obtain the isotropic cross section (powder)
depends on the  point group of the space group
of your crystal.
It is 1 for a cubic or tetraedric crystal,
2 for a uniaxial crystal and it is 3, 4, 6 for a biaxial
(ot trichroic) crystal.
I suggest you read
C. Brouder J. Phys.: Condens. Matter 2 (1990) 701-738
for more details.

M.


> 
> Message: 3
> Date: Sat, 09 Oct 2010 22:48:53 +0800
> From: "wumindt2" 
> Subject: Re: [Pw_forum] Xspectra calculation
> To: pw_forum at pwscf.org
> Message-ID: 
> Content-Type: text/plain; charset="gb2312"
> 
> Dear matteo,
> 
> Thanks. 
> 
> For dichroism compound, do we just need the in-plane and the c-axis
> polarization vectors? 
> While for trichroism compound, do we need to calculate three different
> polarization vectors?
> Am i right?
> 
> Best regards,
> 

[Pw_forum] Xspectra calculation

[wumindt2]

Dear matteo,

Thanks. 

For dichroism compound, do we just need the in-plane and the c-axis
polarization vectors? 
While for trichroism compound, do we need to calculate three different
polarization vectors?
Am i right?

Best regards,

Min Wu
2010-10-9

>From: matteo calandra 
>Reply-To: PWSCF Forum 
>To: pw_forum at pwscf.org
>Subject: Re: [Pw_forum] Xspectra calculation
>Date: Sat,  9 Oct 2010 11:30:54 +0200
>
>Dear Wumindt2,
>
>   the fact that different polarization directions can be equivalent or not
>in a solid depends only on the symmetry of your lattice (thus on the crystal
>structure) only.
>So the general response to your question is given by the theory of crystal
>symmetries.
>
>M.
>
>
>> --
>>
>> Message: 1
>> Date: Sat, 09 Oct 2010 11:11:16 +0800
>> From: "wumindt2"

>> Subject: [Pw_forum] Xspectra calculation
>> To: pw_forum at pwscf.org
>> Message-ID:

>> Content-Type: text/plain; charset="gb2312"
>>
>> Dear Xspectra users,
>>
>> I met a problem when calculating the X-ray absorption spectra with  
>> the Xspectra code.
>> Concern about the polarization, ?// is the polarization along the c  
>> axis, while ?? is the polariztion
>> in the plane.  It's easy to define the ?// , since normally (0,0,1)  
>> is the direction of c axis.
>> But for ?? polarization, what does "in plane" mean? Are any  
>> directions in the a,b plane
>> will cause the same result? For instance, will (1,0,0) ,(0,1,0) or  
>> (1,1,0) polarization direction
>> have the same spectra?
>>
>> Thank you very much for any help.
>>
>> Cheers,
>>
>> Min Wu
>> 2010-10-8
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>> ___
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>>
>>
>> End of Pw_forum Digest, Vol 40, Issue 16
>> 
>>
>
>
>
>
>This message was sent using IMP, the Internet Messaging Program.
>
>
>___
>Pw_forum mailing list
>Pw_forum at pwscf.org
>http://www.democritos.it/mailman/listinfo/pw_forum
> 

[Pw_forum] Xspectra calculation

[matteo calandra]

Dear Wumindt2,

   the fact that different polarization directions can be equivalent or not
in a solid depends only on the symmetry of your lattice (thus on the crystal
structure) only.
So the general response to your question is given by the theory of crystal
symmetries.

M.


> --
>
> Message: 1
> Date: Sat, 09 Oct 2010 11:11:16 +0800
> From: "wumindt2" 
> Subject: [Pw_forum] Xspectra calculation
> To: pw_forum at pwscf.org
> Message-ID: 
> Content-Type: text/plain; charset="gb2312"
>
> Dear Xspectra users,
>
> I met a problem when calculating the X-ray absorption spectra with  
> the Xspectra code.
> Concern about the polarization, ?// is the polarization along the c  
> axis, while ?? is the polariztion
> in the plane.  It's easy to define the ?// , since normally (0,0,1)  
> is the direction of c axis.
> But for ?? polarization, what does "in plane" mean? Are any  
> directions in the a,b plane
> will cause the same result? For instance, will (1,0,0) ,(0,1,0) or  
> (1,1,0) polarization direction
> have the same spectra?
>
> Thank you very much for any help.
>
> Cheers,
>
> Min Wu
> 2010-10-8
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>
> ___
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>
> End of Pw_forum Digest, Vol 40, Issue 16
> 
>




This message was sent using IMP, the Internet Messaging Program.

[Pw_forum] Xspectra calculation

[wumindt2]

Dear Xspectra users,

I met a problem when calculating the X-ray absorption spectra with the Xspectra 
code.
Concern about the polarization, ?// is the polarization along the c axis, while 
?? is the polariztion
in the plane.  It's easy to define the ?// , since normally (0,0,1) is the 
direction of c axis.
But for ?? polarization, what does "in plane" mean? Are any directions in the 
a,b plane
will cause the same result? For instance, will (1,0,0) ,(0,1,0) or (1,1,0) 
polarization direction
have the same spectra?

Thank you very much for any help.

Cheers,

Min Wu
2010-10-8
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