[Pw_forum] convergence of SCF calculation of C6H8

[Masoud]

Dear Ruibin

ibrav(1) means you are using a simple cubic in your calculations and when
you use a large celldm(1)=30 (Bohr) it is clear that your vectors are:

V1=30(1,0,0)
V2=30(0,1,0)
V3=30(0,0,1)

think over !!! you have a very spacious box and a molecule inside it. so
your molecule feel alone. For more details about periodic systems and
crystals please read some pages of an elementary solid state book and the
PW manual. I hope it helps.



Best Wishes, m





----------------------------------------
Masoud Nahali
SUT
masoud.nahali at gmail.com
alum.sharif.edu/~m_nahali





On Sat, Nov 3, 2012 at 10:44 AM, Ruibin Wrote:

>
> Thank you! In QE, we use supercell to isolate a molecule, right? I don't
> understand the differences between isolated and periodic systems in QE.
> Anyway, other parameters are as follows:
>  &system
>     ibrav = 1, celldm(1) =30.0, nat= 14, ntyp= 2,
>     ecutwfc = 30.0, ecutrho = 300.0
>  /
>  &electrons
>     diagonalization='david'
>     electron_maxstep = 50,
>     conv_thr = 1.0e-6
>     mixing_beta = 0.1
> ATOMIC_SPECIES
>  C 12.011   C.blyp-van_ak.UPF
>  H 1.008    H.blyp-van_ak.UPF
> K_POINTS Gamma
>
> How can I change them?
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20121103/c3db49af/attachment.html>