[Wien] optimize & mini for crystal lattice

[Stefaan Cottenier]

Note that wien2k can perform this fit 'automatically', using the 'x  
eosfit' program with a suitable case.vol file (see usersguide). Three  
different equations of stqte (including Murnaghan) are applied  
simultaneously.

Stefaan


> One simple approach would be to fit your results (energy w/r/t volume) using
> the Murnaghan equation. It is given as:
>
> E(V) = E_0 + (B_0 * V) / B1_0 * ( (V_0/V)^B1_0 / (B1_0 - 1) + 1 ) -
>            -  B_0 * V_0 / (B1_0 - 1)
>
> There are 4 parameters
> a0 = E_0 - B_0 * V_0 /  (B1_0 - 1)
> a1 = B_0
> a2 = B1_0
> a3 = V_0
>
> So the fitting equation (using xmgrace for instance) is:
>
> y = a0 + (a1*x)/a2 * ((a3/x)^a2 / (a2-1) + 1)
>
> where x is the volume in atomic units (bohr^3), and y is the energy in
> Hartree units. After the fit, a3 is the equilibrium volume (so take the
> cubic root to have a_0), and a1 is the bulk modulus B_0 in atomic units. How
> to convert atomic units to human units?
>
> a_0 [Ang] = a_0 [bohr] * 0.529177
> B_0 [GPa] = B_0 [a.u.] * 2.9421 * 10^4
>
>
>
>
> ----------------------------------------
> James M Rondinelli
> Materials Department
> University of California, Santa Barbara
> Santa Barbara, CA 93106-5050  USA
> Tel: (805) 893-7934  Fax: (805) 893-8502
> Office: MRL 2236
> Email: rondinelli.at.umail.ucsb.edu
> ----------------------------------------
> -----Original Message-----
> From: wien-bounces at zeus.theochem.tuwien.ac.at
> [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of ???
> Sent: Tuesday, August 29, 2006 18:34
> To: wien at zeus.theochem.tuwien.ac.at
> Subject: [Wien] optimize & mini for crystal lattice
>
> Dear all,
>      I am glad to communicate with you ! Recently, I am performing the
> calculation on the optimization of crystal lattice & the relaxation
> of atomic positions. I had selected a series of volumes of crystal
> and run the commands "optimize" & "mini". In the file optimize.job, I
> adopted  the min -I -j "run_lapw -I -fc 1.0 -i 200 -p" and the file
> as:
>
>> #!/bin/csh -f
>> #   Modify this script according to your needs:
>> #      Uncomment one of the lines ...
>> #      Change run_lapw to runsp_lapw or use different convergence criterium
>> #      Change save_lapw -d XXX
>> foreach i ( \
>>                                         Bi2O3_abc___1.0  \
>>                                         Bi2O3_abc___2.0  \
>>                                         Bi2O3_abc___3.0  \
>>                                         Bi2O3_abc___4.0  \
>>                                         Bi2O3_abc___5.0  \
>>                                         Bi2O3_abc___6.0  \
>>                                         Bi2O3_abc___7.0  \
>>                                         Bi2O3_abc___8.0  \
>>                                         Bi2O3_abc___9.0  \
>>                                         Bi2O3_abc__10.0  \
>> )
>>     cp  $i.struct Bi2O3.struct
>
>> # Please uncomment and adapt any of the lines below according to your
> needs
>> #    cp  $i.clmsum Bi2O3.clmsum
>> #    x dstart
>> #    x dstart -c
>> #    run_lapw -ec 0.0001 -in1new 3 -in1orig -renorm
>> #    runsp_lapw -ec 0.0001
>>      min -I -j "run_lapw -I -fc 1.0 -i 200 -p"
>> #    run_lapw -ec 0.0001
>
>>     set stat = $status
>>     if ($stat) then
>>        echo "ERROR status in" $i
>>        exit 1
>>     endif
>>     save_lapw  $i
>> #    save_lapw  -f -d XXX $i
>> end
>
>     Now, the question is how to analyze the calculated results. That is
> how to determine the equilibrium volume. Am I select the volume of
> minimum total energy from these 10 volumes?
>      Thanks for any help!
>
> Best Wishes!
>
> --
> =====================================================
> Mr. GuoHua Zhong
> Address:
>     Key Laboratory of Materials Physics,Institute
>     of Solid State Physics, Chinese Academy of Sciences
>     Hefei, Anhui P.O.Box 1129, 230031 P. R. China
> Telephone:
>     86-551-5591464 (Office)
> E-Mail:
>     zhgh at theory.issp.ac.cn
>
>
>
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>



-- 
Stefaan Cottenier
Instituut voor Kern- en Stralingsfysica
K.U.Leuven
Celestijnenlaan 200 D
B-3001 Leuven (Belgium)

tel: + 32 16 32 71 45
fax: + 32 16 32 79 85
e-mail: stefaan.cottenier at fys.kuleuven.be


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