Re: [Wien] Question Regarding NMR Calculations and Nuclear quadrupole coupling Constant

[pieper]

To clarify this:

Yes, there is a line shift by nuclear quadrupole interaction, and, 
depending on the size of the EFG, it can be significant for the 
determinatation of chemical shift or even Knight shift. It appears in 
perturbation theory beyond first order, which describes the familiar 
quadrupole splitting. For this you might want to look at


M. H. Cohen and F. Reif,
Quadrupole Effects in Nuclear Magnetic Resonance Studies of Solids,
Solid State Physics, Vol 5
Academic Press, 1957
editors F. Seitz and D. Turnbull

Of course, nowadays you can also do a numerical diagonalization of the 
Hamiltonian for magnetic field and quadrupole interaction.


Best regards,


---
Dr. Martin Pieper
Karl-Franzens University
Institute of Physics
Universitätsplatz 5
A-8010 Graz
Austria
Tel.: +43-(0)316-380-8564


Am 22.11.2017 13:33, schrieb Peter Blaha:

This is a question to NMR-experimentalists. They usually know how they
obtain the CS and quadrupol splitting from their experimental data.

I don't think the quadrupole moment influences the value of the CS.

On 11/22/2017 11:24 AM, sandeep Kumar wrote:

Dear Professor Peter Blaha and Dr. Robert Laskowski,

It is known thatquadrupolar nuclei such as 17O the resonance frequency
is a combination of the chemical shift and the isotropic quadrupole
coupling (goes like Cq^2/w0, Cq is the coupling and w0 is the Larmor
frequency) and for a perfectly symmetric environment it should be 
zero.




I have calculated NMR chemical shift and quadrupole coupling 
constantof

an insulator systems.  My question is how we can calculate the
contributions of Cq in chemical shifts and how much
the quadrupole moment influences the chemical shift?



Please correct me if I am wrong.



Thanks



Sandeep Kumar


--
Dr. Sandeep Kumar, Post-doc
Department of Chemistry,
The Lise Meitner-Minerva Center for Computational Quantum Chemistry &
The Institute for Nanotechnology and Advanced Materials,
Bar-Ilan University, Ramat-Gan 52900, Israel



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Re: [Wien] Question Regarding NMR Calculations and Nuclear quadrupole coupling Constant

[Peter Blaha]

This is a question to NMR-experimentalists. They usually know how they 
obtain the CS and quadrupol splitting from their experimental data.


I don't think the quadrupole moment influences the value of the CS.

On 11/22/2017 11:24 AM, sandeep Kumar wrote:

Dear Professor Peter Blaha and Dr. Robert Laskowski,

It is known thatquadrupolar nuclei such as 17O the resonance frequency
is a combination of the chemical shift and the isotropic quadrupole
coupling (goes like Cq^2/w0, Cq is the coupling and w0 is the Larmor
frequency) and for a perfectly symmetric environment it should be zero.



I have calculated NMR chemical shift and quadrupole coupling constantof
an insulator systems.  My question is how we can calculate the
contributions of Cq in chemical shifts and how much
the quadrupole moment influences the chemical shift?



Please correct me if I am wrong.



Thanks



Sandeep Kumar


--
Dr. Sandeep Kumar, Post-doc
Department of Chemistry,
The Lise Meitner-Minerva Center for Computational Quantum Chemistry &
The Institute for Nanotechnology and Advanced Materials,
Bar-Ilan University, Ramat-Gan 52900, Israel



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--

  P.Blaha
--
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.atWIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
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[Wien] Question Regarding NMR Calculations and Nuclear quadrupole coupling Constant

[sandeep Kumar]

Dear Professor Peter Blaha and Dr. Robert Laskowski,

It is known that quadrupolar nuclei such as 17O the resonance frequency is
a combination of the chemical shift and the isotropic quadrupole coupling
(goes like Cq^2/w0, Cq is the coupling and w0 is the Larmor frequency) and
for a perfectly symmetric environment it should be zero.



I have calculated NMR chemical shift and quadrupole coupling constant of an
insulator systems.  My question is how we can calculate the contributions
of Cq in chemical shifts and how much the quadrupole moment influences the
chemical shift?



Please correct me if I am wrong.



Thanks



Sandeep Kumar

-- 
Dr. Sandeep Kumar, Post-doc
Department of Chemistry,
The Lise Meitner-Minerva Center for Computational Quantum Chemistry &
The Institute for Nanotechnology and Advanced Materials,
Bar-Ilan University, Ramat-Gan 52900, Israel
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Re: [Wien] Question regarding spin scaling (xc1) implementation in wien2k

[Peter Blaha]

No, the total energy has not been implemented. Only the potential.

Am 07.07.2016 um 02:37 schrieb Wen Fong Goh:

Dear wien2k developers,


I would like to know does the wien2k calculation with spin scaling (xc1)
give a consistent total energy value? I looked up the subroutines in
SRC_lapw0, particularly in vxclm2.f and only found the scaled exchange
potential:

vhelp=vxu
vxu=(vxu*(1.d0+xc1)+vxd*(1-d0-xc1))/2.d0
vxd=(vhelp*(1.d0-xc1)+vxd*(1-d0+xc1))/2.d0
I wonder if it also gives the total energy. Also, I have problem finding
where the total energy is calculated, can anyone point it out to me? Thanks.



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--
--
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982
Email: bl...@theochem.tuwien.ac.atWIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/staff/tc_group_e.php
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Re: [Wien] Question regarding wien2wannier for wannier.spn file

[Elias Assmann]

On 03/17/2016 02:54 PM, Santu Baidya wrote:
> There is module kpath to plot the energy bands coloured by the 
> expectation value of the spin along [001]:
> 
> " Error: Problem opening input file wannier.spn Error on node 0:
> examine the output/error files for details"
> 
> Can anyone please help me to overcome this problem. Does
> wien2wannier support spin as a function of k vector information to
> write?

Short answer: no.

In general, the new postw90 offers quite a lot of functionality that,
unfortunately, wien2wannier/Wien2k does not support.

As for case.spn specifically, the Wannier90 user's guide tells me:

  write_spn – Set to .true. to write out the matrix elements of S
between Bloch states (non-collinear spin calculation only).

I am not sure I understand why that would be useful only for a
non-collinear calculation.  I do not think that Wien2k provides this
data directly, but it seems like it should be doable (with SOC, of
course).


Elias

-- 
Elias Assmann

Wien2Wannier: maximally localized Wannier functions
  from linearized augmented plane waves





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[Wien] QUESTION regarding p-n junction DOS

[prasenjit roy]

Dear Prof. Blaha and WIEN2K users,

I have a question regarding physics. We tried to do a calculation for an
organic(p-type)-inorganic(n-type) interface for p-n junction photodiode.
First we did a calculation for organic part, then the inorganic part and
finally both together. All three of them were performed for the same
unitcell size.

But while plotting DOSfor the interface, the organic donor [p-type](as
reported in literature) DOS shifts to lower energy, making it n-type.

I do not know where is the problem. Some literature suggests that part of
the DOS (organic part) need to be shifted with respect to the vacuum level.
How to do that?

I will be highly obliged if you can kindly give me your suggestions
regarding this.

Thank you very much, with kind regards,
Prasenjit Roy
Electronic Structures of Materials
Radboud University
Nijmegen
+31 (0) 24 36 52805
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Re: [Wien] question regarding magetic moment

[Xavier Rocquefelte]

Dear Rishi
Indeed, WIEN2K provides numbers with 4 digits however it does not mean that the 
value is accurate up to 4 digits. 
The accuracy will depend on:
- the convergence criteria you are using. 
- the RMT you are using. Indeed the magnetic moment for each atom is estimated 
inside the muffin-tin radius you have defined. If you use small RMT you will 
have a significant discrepancy. 

In addition, you must think about the experimental accuracy. For magnetic 
moment, I usually consider 2 digits not more. 

Regards
Xavier

Rishi Singh rishising...@gmail.com a écrit :

 Dear wien users

 I am unable to know that what is accuracy of magnetic moment calculated by
 wien2k package. Is it true that its accuracy is not up to .0001

 Please help me regarding this.

 I will be highly obliged. Thanks in advance.



 kind regard

 Dr R P Singh
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[Wien] question regarding magetic moment

[Rishi Singh]

Dear wien users

I am unable to know that what is accuracy of magnetic moment calculated by
wien2k package. Is it true that its accuracy is not up to .0001

Please help me regarding this.

I will be highly obliged. Thanks in advance.



kind regard

Dr R P Singh
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[Wien] question regarding

[Muhammad Sajjad]

Dear user
I switched to new work place in another lab with different internet
settings. when i wrote w2web in terminal, i received the following message
(w2web server started, now point your web browser to
http://msajjad:7890), same a before.

When I opened the address (http://msajjad:7890), it is not running (The
server at www.msajjad.com is taking too long to respond). Do I need to
delete w2web folder and set it again or any other solution please?

With thanks
M. Sajjad
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Re: [Wien] question regarding

[pieper]

It seems, Wien2k is running on your local machine? My guess is, that you 
changed the name of your machine ('msajjad') when you moved and should 
setup w2web new.


If Wien2k is not running on your local machine there is probably now a 
firewall between your new place and the machine running Wien2k. Look 
into the firewall settings of the machine running Wien2k and the network 
servers in between.


Good look!


---
Dr. Martin Pieper
Karl-Franzens University
Institute of Physics
Universitätsplatz 5
A-8010 Graz
Austria
Tel.: +43-(0)316-380-8564


Am 07.05.2014 09:56, schrieb Muhammad Sajjad:

Dear user
I switched to new work place in another lab with different internet
settings. when i wrote w2web in terminal, i received the following
message (w2web server started, now point your web browser to
http://msajjad:7890 [1]), same a before.

When I opened the address (http://msajjad:7890 [1]), it is not running
(The server at www.msajjad.com [2] is taking too long to respond). Do
I need to delete w2web folder and set it again or any other solution
please?

With thanks
M. Sajjad

Links:
--
[1] http://msajjad:7890
[2] http://www.msajjad.com

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Re: [Wien] question regarding

[Muhammad Sajjad]

Dear Pieper

Thank you for your response. I build new w2web after removing the old one,
and now it is working.

Kind Regards
M. Sajjad


On Wed, May 7, 2014 at 6:09 PM, pieper pie...@ifp.tuwien.ac.at wrote:

 It seems, Wien2k is running on your local machine? My guess is, that you
 changed the name of your machine ('msajjad') when you moved and should
 setup w2web new.

 If Wien2k is not running on your local machine there is probably now a
 firewall between your new place and the machine running Wien2k. Look into
 the firewall settings of the machine running Wien2k and the network servers
 in between.

 Good look!


 ---
 Dr. Martin Pieper
 Karl-Franzens University
 Institute of Physics
 Universitätsplatz 5
 A-8010 Graz
 Austria
 Tel.: +43-(0)316-380-8564


 Am 07.05.2014 09:56, schrieb Muhammad Sajjad:

 Dear user
 I switched to new work place in another lab with different internet
 settings. when i wrote w2web in terminal, i received the following
 message (w2web server started, now point your web browser to
 http://msajjad:7890 [1]), same a before.

 When I opened the address (http://msajjad:7890 [1]), it is not running
 (The server at www.msajjad.com [2] is taking too long to respond). Do

 I need to delete w2web folder and set it again or any other solution
 please?

 With thanks
 M. Sajjad

 Links:
 --
 [1] http://msajjad:7890
 [2] http://www.msajjad.com

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Re: [Wien] Question regarding simultaneous optimization of lattice parameters and atomic coordinates

[Peter Blaha]

Forget the   case_1, ..2,... files. These are intermediate files during force 
optimization.

As you said, you will get final case_abc_1.scf, ..2,.. files. They should have 
small forces (check it out)
and have optimized internal positions. These files (energies) and the 
corresponding struct files
should be used for analysis.

Am 12.03.2014 04:54, schrieb shamik chakrabarti:

Dear wien2k users,

  I have started simultaneous optimization of a,b,c of an 
orthorhombic lattice by using Option 6 in structure optimization script.

I have also comment (#) runsp_lapw and uncomment min_lapw in optimize.job 
such that the script should do force minimization of each struct files prepared during x
optimize.

Now, the script will copy case_abc_1.struct to case.struct and this file will then be 
used by min_lapw... and save the results as case_1.struct. This procedure 
will be
continued for each of the struct files generated during x optimize.

Now after completing the whole process we will get several scf files named as 
case_abc_1.scf, case_abc_2.scf,...etc. which can be used to find optimized 
a.b.c.

Also, after min_lapw... new structure files are getting saved like 
case_1.struct, case_2.struct...etc for a particular case_abc_i struct files

So my question is,

after completing the whole process we will ultimately get case_1.scf, 
case_2.scf generated from the last case_abc_i type files...and we can not get 
force optimized files
for each case_abc_i type files...is it true?

If it is truethen what should we do to get force optimized struct files for 
each case_abc_i type files such that we can achieve simultaneous optimization 
of a,b,c and
force for the orthorhombic lattice?

Any response in this regard is eagerly awaited.

Thanks in advance,

with regards,
--
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics  Meteorology
Material Processing  Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA


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--
-
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pbl...@theochem.tuwien.ac.at
-
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Re: [Wien] Question regarding simultaneous optimization of lattice parameters and atomic coordinates

[shamik chakrabarti]

Sir,

 Thank you Sir. Thank you very much for your response.

with regards,


On Wed, Mar 12, 2014 at 11:47 AM, Peter Blaha
pbl...@theochem.tuwien.ac.atwrote:

 Forget the   case_1, ..2,... files. These are intermediate files during
 force optimization.

 As you said, you will get final case_abc_1.scf, ..2,.. files. They should
 have small forces (check it out)
 and have optimized internal positions. These files (energies) and the
 corresponding struct files
 should be used for analysis.

 Am 12.03.2014 04:54, schrieb shamik chakrabarti:

 Dear wien2k users,

   I have started simultaneous optimization of a,b,c
 of an orthorhombic lattice by using Option 6 in structure optimization
 script.

 I have also comment (#) runsp_lapw and uncomment min_lapw in
 optimize.job such that the script should do force minimization of each
 struct files prepared during x
 optimize.

 Now, the script will copy case_abc_1.struct to case.struct and this file
 will then be used by min_lapw... and save the results as case_1.struct.
 This procedure will be
 continued for each of the struct files generated during x optimize.

 Now after completing the whole process we will get several scf files
 named as case_abc_1.scf, case_abc_2.scf,...etc. which can be used to find
 optimized a.b.c.

 Also, after min_lapw... new structure files are getting saved like
 case_1.struct, case_2.struct...etc for a particular case_abc_i struct files

 So my question is,

 after completing the whole process we will ultimately get case_1.scf,
 case_2.scf generated from the last case_abc_i type files...and we can not
 get force optimized files
 for each case_abc_i type files...is it true?

 If it is truethen what should we do to get force optimized struct
 files for each case_abc_i type files such that we can achieve simultaneous
 optimization of a,b,c and
 force for the orthorhombic lattice?

 Any response in this regard is eagerly awaited.

 Thanks in advance,

 with regards,
 --
 Shamik Chakrabarti
 Senior Research Fellow
 Dept. of Physics  Meteorology
 Material Processing  Solid State Ionics Lab
 IIT Kharagpur
 Kharagpur 721302
 INDIA


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 --
 -
 Peter Blaha
 Inst. Materials Chemistry, TU Vienna
 Getreidemarkt 9, A-1060 Vienna, Austria
 Tel: +43-1-5880115671
 Fax: +43-1-5880115698
 email: pbl...@theochem.tuwien.ac.at
 -
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-- 
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics  Meteorology
Material Processing  Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA
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Re: [Wien] Question regarding volume expansion-contraction after extraction of Li ions

[Peter Blaha]

You cannot expect that a,b,c is correct when you fix atomic positions 
(which are allowed to vary according to symmetry). But without doing 
these calculations (or at least checking how large are the forces in 
your best structure) one cannot say anything.


On the other hand: I do not know if the VASP calculation is correct 
either ...




On 03/10/2014 08:06 AM, shamik chakrabarti wrote:

Dear Prof. Blaha,

*we have also used the option 6 for optimization of delithiated
compound...but in that case also we have obtained decrements in unit
cell volume with Li ion extraction.*

We have also used GGA, and GGA+U for lattice parameter optimization. As,
usual with GGA+U approach we have obtained higher lattice parameters
than the case with GGA. However, decrements of unit cell volume with Li
extraction has been apparent for both the cases.

Yes it could be the fact that we may need to modify the script for
simultaneous optimization of coordinates with lattice parameter
optimizationwhether it could lead to the solution?whether the
decrements of unit cell volume with Li delithiation can be avoided  we
actually will get an increment by this method?.

Most importantly, although we are getting a volume reduction with Li
de-intercalation (opposite to VASP)...we are getting very well matched
values of density of states and voltage (from total energy consideration).

Looking forward to your further discussion which may shed some light
over our problems.

with regards,


On Mon, Mar 10, 2014 at 12:16 PM, Peter Blaha
pbl...@theochem.tuwien.ac.at mailto:pbl...@theochem.tuwien.ac.at wrote:

The options optimize vol, c/a or b/a are special options for
certain properties, but for sure a sequential optimization along
these lines does NOT give the minimum a,b,c.

In your case it seems you should use option [6], vary a,b,c.

Furthermore: it is vital, that you optimize internal coordinates
(MSR1a or min_lapw) for each of these steps (modify the resulting
script).

When you are talking about Fe2+,3+; you have to think whether GGA+U
is necessary ??


On 03/10/2014 06:32 AM, shamik chakrabarti wrote:

Dear wien2k users,

   We have simulated structural, elcetronic properties and
cathode
characteristics (in terms of voltage) of a Li based material.
When we
extract some Li ions from the parent compounds and optimize its
volume
and lattice parameters, we have obtained a decrements in volume.
This
decrements has been followed from the concern that Fe+2 ion get
oxidized
in Fe+3 ions in the delithiated compounds  hence there is an
decrements
in Fe-O bond length in comparison to the parent (lithiated) one.

However, simulation report on the same compound, computed in
VASP, has
shown that there is actually an expansion of volume after Li
extraction.
This expansion occurs as when Li ions are taken out from the parent
materials there is a decrements of attraction between two layers
connected with Li ions previously. At least this is the explanation
given by earlier researchers.

we optimize the material and its Li extracted counterpart by
following
the methods:
(1) volume optimization by keeping a:b:c constant, (2)
optimizing c/a
ratio and (3) optimizing b/a ratio

we have taken lattice parameters after (3) rd operation
(optimization)
and calculated  DOS and voltage.

we have also seenthat after 3rd optimization

(1) there is an increment in b/a ratio in the delithiated part
than in
the lithiated part in agreement with VASP
(2) However, unit cell volume of the de-lithiated part is less
than the
lithiated compound due to more dominant reduction of Fe-O bond
lengths
in comparison to the increment of layer-layer separation due to
Li ion
extractions in our calculation.

Now my queries are:

(1) Is the reduction of Fe-O bond length after Li extraction is more
than the decrements of layer-layer separation in FPLAPW
calculation?...
that's why we have achieved decrements of volume instead of
increments
as obtained in VASP?

(2) Whether this difference came out from some inherent fact of
FPLAPW
and PAW (VASP) approach?

(3) Whether this is the limitation of the wien2k code itself?

(4) Or, whether our methodology of calculation by first volume
optimization  then further optimizing c/a and b/a rationis
actually
a wrong path... we should choose some other way for lattice
parameter
optimization after Li extraction.

Sorry for such a long email. However, the answer of these
queries are
very necessary for 

Re: [Wien] Question regarding volume expansion-contraction after extraction of Li ions

[shamik chakrabarti]

Sir,

 The forces in our fully optimized structure is less than 3mRy/a.u. per
atom...also we have done coordinate optimization by taking fully optimized
lattice parameters..

Yes...we have not done the simultaneous optimization of lattice parameters
and atomic coordinates...while we have done all the optimizations in steps:
volume, c/a, b/a, atomic coordinates.

Also, there are several peer reviewed papers on calculation on the same
material with VASP and they have all achieved volume expansion...

Sir...is this mean ...from this discussion..it is coming out that we should
try with simultaneous optimization of lattice parameters and atomic
coordinates for final verification?

but as the energy is mainly depends on volume... not on the lattice
parameters...I really have doubt whether this method would change the trend
of volume contraction towards expansion.


On Mon, Mar 10, 2014 at 12:46 PM, Peter Blaha
pbl...@theochem.tuwien.ac.atwrote:

 You cannot expect that a,b,c is correct when you fix atomic positions
 (which are allowed to vary according to symmetry). But without doing these
 calculations (or at least checking how large are the forces in your best
 structure) one cannot say anything.

 On the other hand: I do not know if the VASP calculation is correct either
 ...



 On 03/10/2014 08:06 AM, shamik chakrabarti wrote:

 Dear Prof. Blaha,

 *we have also used the option 6 for optimization of delithiated

 compound...but in that case also we have obtained decrements in unit
 cell volume with Li ion extraction.*


 We have also used GGA, and GGA+U for lattice parameter optimization. As,
 usual with GGA+U approach we have obtained higher lattice parameters
 than the case with GGA. However, decrements of unit cell volume with Li
 extraction has been apparent for both the cases.

 Yes it could be the fact that we may need to modify the script for
 simultaneous optimization of coordinates with lattice parameter
 optimizationwhether it could lead to the solution?whether the
 decrements of unit cell volume with Li delithiation can be avoided  we
 actually will get an increment by this method?.

 Most importantly, although we are getting a volume reduction with Li
 de-intercalation (opposite to VASP)...we are getting very well matched
 values of density of states and voltage (from total energy consideration).

 Looking forward to your further discussion which may shed some light
 over our problems.

 with regards,


 On Mon, Mar 10, 2014 at 12:16 PM, Peter Blaha
 pbl...@theochem.tuwien.ac.at mailto:pbl...@theochem.tuwien.ac.at
 wrote:

 The options optimize vol, c/a or b/a are special options for
 certain properties, but for sure a sequential optimization along
 these lines does NOT give the minimum a,b,c.

 In your case it seems you should use option [6], vary a,b,c.

 Furthermore: it is vital, that you optimize internal coordinates
 (MSR1a or min_lapw) for each of these steps (modify the resulting
 script).

 When you are talking about Fe2+,3+; you have to think whether GGA+U
 is necessary ??


 On 03/10/2014 06:32 AM, shamik chakrabarti wrote:

 Dear wien2k users,

We have simulated structural, elcetronic properties and
 cathode
 characteristics (in terms of voltage) of a Li based material.
 When we
 extract some Li ions from the parent compounds and optimize its
 volume
 and lattice parameters, we have obtained a decrements in volume.
 This
 decrements has been followed from the concern that Fe+2 ion get
 oxidized
 in Fe+3 ions in the delithiated compounds  hence there is an
 decrements
 in Fe-O bond length in comparison to the parent (lithiated) one.

 However, simulation report on the same compound, computed in
 VASP, has
 shown that there is actually an expansion of volume after Li
 extraction.
 This expansion occurs as when Li ions are taken out from the
 parent
 materials there is a decrements of attraction between two layers
 connected with Li ions previously. At least this is the
 explanation
 given by earlier researchers.

 we optimize the material and its Li extracted counterpart by
 following
 the methods:
 (1) volume optimization by keeping a:b:c constant, (2)
 optimizing c/a
 ratio and (3) optimizing b/a ratio

 we have taken lattice parameters after (3) rd operation
 (optimization)
 and calculated  DOS and voltage.

 we have also seenthat after 3rd optimization

 (1) there is an increment in b/a ratio in the delithiated part
 than in
 the lithiated part in agreement with VASP
 (2) However, unit cell volume of the de-lithiated part is less
 than the
 lithiated compound due to more dominant reduction of Fe-O bond
   

Re: [Wien] Question regarding volume expansion-contraction after extraction of Li ions

[Peter Blaha]

How large are the forces during the vol,ca,ba optimization (before you 
have done a final optimization) ?


I do not know anything about the specific material or details of your 
results or the VASP calculations. How should I guide you ?


I only know that technical one must optimize ALWAYS simultaneously these 
parameters. Of course, in certain cases, there could be negligible 
effects ...


On 03/10/2014 08:29 AM, shamik chakrabarti wrote:

Sir,

  The forces in our fully optimized structure is less than 3mRy/a.u.
per atom...also we have done coordinate optimization by taking fully
optimized lattice parameters..

Yes...we have not done the simultaneous optimization of lattice
parameters and atomic coordinates...while we have done all the
optimizations in steps: volume, c/a, b/a, atomic coordinates.

Also, there are several peer reviewed papers on calculation on the same
material with VASP and they have all achieved volume expansion...
Sir...is this mean ...from this discussion..it is coming out that we
should try with simultaneous optimization of lattice parameters and
atomic coordinates for final verification?

but as the energy is mainly depends on volume... not on the lattice
parameters...I really have doubt whether this method would change the
trend of volume contraction towards expansion.


On Mon, Mar 10, 2014 at 12:46 PM, Peter Blaha
pbl...@theochem.tuwien.ac.at mailto:pbl...@theochem.tuwien.ac.at wrote:

You cannot expect that a,b,c is correct when you fix atomic
positions (which are allowed to vary according to symmetry). But
without doing these calculations (or at least checking how large are
the forces in your best structure) one cannot say anything.

On the other hand: I do not know if the VASP calculation is correct
either ...



On 03/10/2014 08:06 AM, shamik chakrabarti wrote:

Dear Prof. Blaha,

*we have also used the option 6 for optimization of delithiated

compound...but in that case also we have obtained decrements in unit
cell volume with Li ion extraction.*


We have also used GGA, and GGA+U for lattice parameter
optimization. As,
usual with GGA+U approach we have obtained higher lattice parameters
than the case with GGA. However, decrements of unit cell volume
with Li
extraction has been apparent for both the cases.

Yes it could be the fact that we may need to modify the script for
simultaneous optimization of coordinates with lattice parameter
optimizationwhether it could lead to the
solution?whether the
decrements of unit cell volume with Li delithiation can be
avoided  we
actually will get an increment by this method?.

Most importantly, although we are getting a volume reduction with Li
de-intercalation (opposite to VASP)...we are getting very well
matched
values of density of states and voltage (from total energy
consideration).

Looking forward to your further discussion which may shed some light
over our problems.

with regards,


On Mon, Mar 10, 2014 at 12:16 PM, Peter Blaha
pbl...@theochem.tuwien.ac.at
mailto:pbl...@theochem.tuwien.ac.at
mailto:pblaha@theochem.__tuwien.ac.at
mailto:pbl...@theochem.tuwien.ac.at wrote:

 The options optimize vol, c/a or b/a are special
options for
 certain properties, but for sure a sequential optimization
along
 these lines does NOT give the minimum a,b,c.

 In your case it seems you should use option [6], vary a,b,c.

 Furthermore: it is vital, that you optimize internal
coordinates
 (MSR1a or min_lapw) for each of these steps (modify the
resulting
 script).

 When you are talking about Fe2+,3+; you have to think
whether GGA+U
 is necessary ??


 On 03/10/2014 06:32 AM, shamik chakrabarti wrote:

 Dear wien2k users,

We have simulated structural, elcetronic
properties and
 cathode
 characteristics (in terms of voltage) of a Li based
material.
 When we
 extract some Li ions from the parent compounds and
optimize its
 volume
 and lattice parameters, we have obtained a decrements
in volume.
 This
 decrements has been followed from the concern that Fe+2
ion get
 oxidized
 in Fe+3 ions in the delithiated compounds  hence there
is an
 decrements
 in Fe-O bond length in comparison to the parent
(lithiated) one.

 However, simulation report on the same compound,
computed in
 

[Wien] Question regarding volume expansion-contraction after extraction of Li ions

[shamik chakrabarti]

Dear wien2k users,

 We have simulated structural, elcetronic properties and cathode
characteristics (in terms of voltage) of a Li based material. When we
extract some Li ions from the parent compounds and optimize its volume and
lattice parameters, we have obtained a decrements in volume. This
decrements has been followed from the concern that Fe+2 ion get oxidized in
Fe+3 ions in the delithiated compounds  hence there is an decrements in
Fe-O bond length in comparison to the parent (lithiated) one.

However, simulation report on the same compound, computed in VASP, has
shown that there is actually an expansion of volume after Li extraction.
This expansion occurs as when Li ions are taken out from the parent
materials there is a decrements of attraction between two layers connected
with Li ions previously. At least this is the explanation given by earlier
researchers.

we optimize the material and its Li extracted counterpart by following the
methods:
(1) volume optimization by keeping a:b:c constant, (2) optimizing c/a ratio
and (3) optimizing b/a ratio

we have taken lattice parameters after (3) rd operation (optimization) and
calculated  DOS and voltage.

we have also seenthat after 3rd optimization

(1) there is an increment in b/a ratio in the delithiated part than in the
lithiated part in agreement with VASP
(2) However, unit cell volume of the de-lithiated part is less than the
lithiated compound due to more dominant reduction of Fe-O bond lengths in
comparison to the increment of layer-layer separation due to Li ion
extractions in our calculation.

Now my queries are:

(1) Is the reduction of Fe-O bond length after Li extraction is more than
the decrements of layer-layer separation in FPLAPW calculation?... that's
why we have achieved decrements of volume instead of increments as obtained
in VASP?

(2) Whether this difference came out from some inherent fact of FPLAPW and
PAW (VASP) approach?

(3) Whether this is the limitation of the wien2k code itself?

(4) Or, whether our methodology of calculation by first volume optimization
 then further optimizing c/a and b/a rationis actually a wrong
path... we should choose some other way for lattice parameter optimization
after Li extraction.

Sorry for such a long email. However, the answer of these queries are very
necessary for our further research and I believe, this discussion will help
the community as a whole.

Thanks in advance,

with regards,

-- 
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics  Meteorology
Material Processing  Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA
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[Wien] Question regarding volume optimization

[shamik chakrabarti]

Dear wien2k users,

I have a query regarding volume optimization in wien2k. Option 1
optimizes the volume by keeping a:b:c = constant. Now my question is:

in which case this Option 1 is applicable?...is it only applicable for
cubic symmetry?

Any response in this regard will be helpful for us. Thanks in advance.

with regards,
-- 
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics  Meteorology
Material Processing  Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA
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Re: [Wien] Question regarding volume optimization

[Stefaan Cottenier]

I have a query regarding volume optimization in wien2k. Option 1
optimizes the volume by keeping a:b:c = constant. Now my question is:

in which case this Option 1 is applicable?...is it only applicable for
cubic symmetry?


You can use it for any crystal. Very often, the total energy will 
depends much more on the volume than on the c/a- or b/a-ratio.


The difference between cubic and other crystals is that for a cubic 
crystal it is meaningless to vary anything else than the volume.


Similarly, for a tetragonal crystal you can change the volume and c/a, 
but not b/a. For an orthorombic crystal can change volume, c/a, b/a. Etc.


Stefaan

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Re: [Wien] Question regarding volume optimization

[shamik chakrabarti]

Dear Stefaan Cottenier Sir,

  Thank you very much for your response. We got our answer.

with regards,


On Wed, Jun 19, 2013 at 3:03 PM, Stefaan Cottenier 
stefaan.cotten...@ugent.be wrote:


  I have a query regarding volume optimization in wien2k. Option 1
 optimizes the volume by keeping a:b:c = constant. Now my question is:

 in which case this Option 1 is applicable?...is it only applicable for
 cubic symmetry?


 You can use it for any crystal. Very often, the total energy will depends
 much more on the volume than on the c/a- or b/a-ratio.

 The difference between cubic and other crystals is that for a cubic
 crystal it is meaningless to vary anything else than the volume.

 Similarly, for a tetragonal crystal you can change the volume and c/a, but
 not b/a. For an orthorombic crystal can change volume, c/a, b/a. Etc.

 Stefaan

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-- 
Shamik Chakrabarti
Senior Research Fellow
Dept. of Physics  Meteorology
Material Processing  Solid State Ionics Lab
IIT Kharagpur
Kharagpur 721302
INDIA
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