[Pw_forum] Bulk Modulus Calculation

[Duy Le]

it seems that you don't know how bulk modulus is actually calculated.
It is -V(d^2E/dV^2). So you need to vary the volume, calculate total
energy then fit the data to equation of states (I think ev.f90 do this
job, I am not so sure. But in any case, you can always fit these data
to equation of states by any other programs or codes). Once you have
equation of states, calculate -V(d^2E/dV^2) at the minimum >>> this is
bulk modulus.

I suggest that you should have look a http://www.pwscf.org/wiki/index.php/QESB09
and follow the Lab tutorial on Monday 20, July 2009.
The week1_day1_exersice1 is about optimizing lattice parameter,
equation of states (that includes bulk modulus)

--------------------------------------------------
Duy Le
PhD Student
Department of Physics
University of Central Florida.

"Men don't need hand to do things"



On Tue, Jan 4, 2011 at 5:06 PM, Tram Bui <trambui at u.boisestate.edu> wrote:
> Hi All,
>      Hope everyone had great holidays, I had a question before regarding the
> Bulk Modulus calculation (ev.f90) But I'm having hard time understand  the
> file and don't know how to use the ev.f to help me calculate the bulk
> modulus if I have an input file is like below and the structure is zinc
> blend (b-SiC). Would you help me if you get a chance? here is my file and
> you can run it in xcyrsden to see the structure.
>
> &CONTROL
>    calculation='scf'
>    restart_mode='from_scratch',
>    prefix='Silicon',
>    tprnfor=.true.
>    pseudo_dir='/home/trambui/QE/espresso-4.2.1/pseudo',
>    outdir='./tmp7/',
> /
> &SYSTEM
>    ibrav=2, celldm(1)=8.33, nat=2, ntyp=2,
>    ecutwfc= 30,
> /
> &ELECTRONS
>    diagonalization= 'david',
>    mixing_mode= 'plain',
>    mixing_beta= 0.5,
>    conv_thr= 1.0d-7,
> /
> ATOMIC_SPECIES
> Si 28.086 Si.pbe-n-van.UPF
>  C 12.011 C.pbe-van_ak.UPF
> ATOMIC_POSITIONS
> Si 0.00 0.00 0.00
>  C 0.25 0.25 0.25
> K_POINTS automatic
> 10 10 10 0 0 0
>
> I really appreciate your helps!
>
> Tram Bui
>
> B.S. Materials Science & Engineering
> trambui at u.boisestate.edu
>
>
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