[Pw_forum] cohesive energy of tungsten

[mohnish pandey]

Dear Vicky!
                   Check the convergence of energy of isolated atoms also.
Normally convergence threshold for energy for isolated species is higher
than the crystal system. Check for different values of ecut and use the
converged value. And next thing is you are doing calculations for bulk
system so all the degrees of freedom should be relaxed for geometry
optimization so instead of flag "relax" use "vc-relax".. The former one will
converge the forces but not the stress and latter one converges the stress
also...
On Sun, Dec 5, 2010 at 11:53 AM, vicky singh <kirtinandan07 at gmail.com>wrote:

> Hi
>
> I am trying to calculate the cohesive energy for tungsten. the code is
> attached. I am able to get the lattice parameter of 3.19 ang while
> experimental is 3.16 angs. Then i calculated the cohesive energy of w by
> calculating the energy of isolated w atom by changing  lattice parameter up
> to 25. I got the cohesive energy of 11.1 ev/atom while reported value is 8.9
> ev/atom. This is way too high. can anybody help me. I have varied the K
> point as well as The E_cut but no advantage.
>
> vicky singh
> research student
> Bangalore
>
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>


-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
Y6927262,5th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
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