[Pw_forum] using ev.x

[Stefano Baroni]

look at the two fitted equations of state (draw pictures) and see  
which one fits best the raw data
SB

On Sep 8, 2009, at 10:09 PM, udayagiri sai babu wrote:

> Dear stefano baroni
> I tried that as well i am getting the same value (255gpa). This is  
> the data i am using
>
> 5.35    -174.156857800
> 5.36    -174.156934850
> 5.37    -174.156989300
> 5.38    -174.156990580
> 5.39    -174.156955990
> 5.4    -174.156869280
>
> this is one of the input file
>
>  &control
> calculation = 'scf',
> restart_mode='from_scratch',
> outdir='/home/sai/temp',
> prefix='chromium'
> pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',
> tstress = .TRUE.,
> tprnfor = .TRUE.,
> /
> &system
> ibrav=3
> celldm(1)=5.350000,
> nat=1,
> ntyp=1
> ecutwfc=30,
> ecutrho=300,
> occupations='smearing',
> smearing='mv',
> degauss=0.012000
> /
> &electrons
> conv_thr=1.D-8,
> diagonalization='david',
> mixing_mode='plain',
> mixing_beta= 0.7
> /
> ATOMIC_SPECIES
> Cr  51.9961  Cr.pw91-sp-van.UPF
> ATOMIC_POSITIONS (crystal)
> Cr     0.00000000    0.00000000    0.00000000
> K_POINTS {automatic}
> 12 12 12 0 0 0
>
> can you suggest me anything
>
> On Wed, Sep 9, 2009 at 1:03 AM, Stefano Baroni <baroni at sissa.it>  
> wrote:
> How about trying to fit a very accurate set of data around the  
> minimum with a parabola and calculate thus the bulk modulus? Have  
> you tries to plot the resulting fitted curves? which one fits best  
> the raw data? Udaygiri: in Science (as well as in Life) there is no  
> free lunch ... Enjoy Science, no less than Life. SB
>
> On Sep 8, 2009, at 9:04 PM, udayagiri sai babu wrote:
>
>>
>> hi all
>> i am using ev.x file given in the pw_tools directory to calculate  
>> bulk modulus and lattice parameter values of chromium. i used  
>> murnaghan equation of state to fit my data i got bulk modulus of  
>> 256 gpa where as my experimental  value is 160 gpa but when i used  
>> keane equation of state to fit the same data i got 148 gpa bulk  
>> modulus
>>
>> why is this much variation? which equation of state should i use  
>> for cr? because for vanadium and Ti murnagan euation of state has  
>> given reasonable (<20% error) values of bulk modulus but not for Cr
>>
>> please give some suggestions
>> -- 
>> U.Saibabu
>> PhD student,
>> Deformation mechanisms modeling group,
>> Materials engineering department,
>> IISc Bangalore,
>> India.
>>
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>
> ---
> Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
> Trieste
> http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) /  
> stefanobaroni (skype)
>
> La morale est une logique de l'action comme la logique est une  
> morale de la pensée - Jean Piaget
>
> Please, if possible, don't  send me MS Word or PowerPoint attachments
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>
>
> -- 
> U.Saibabu
> PhD student,
> Deformation mechanisms modeling group,
> Materials engineering department,
> IISc Bangalore,
> India.
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale  
de la pensée - Jean Piaget

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html







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