[Pw_forum] scf calculation for isolated hydrogen atoms

[Ngoc Linh Nguyen]

Dimpy Sharma wrote:
>
> Hi there,
> I tried to calculate the ground state energy for isolated hydrogen 
> atom with the following input,however I got the fermi energy level at 
> -3.5661eV, while it should be -13.6eV.
>
Firstly, you should consider about the difference of the ground state 
energy of an isolated Hydrogen atom and the ground state energy of a 
periodic boundary condition system (it is similar to the bulk of Hydrogen).

If you want to calculate an isolated hydrogen atom, I suggest to use 
Atomic Calculation ld1.x better than to use PWSCF.

Secondly, If you still want to use PWSCF, I think you should reconsider:
   - celldm(1) =15. That should be large enough.
    -  nbnd = 2,   nspin=2,   starting_magnetization(1)=0.5  ???. I 
think you are wrong here because hydrogen have only 1 electron.
   
Linh




> &CONTROL.
>      calculation ='scf'
>     restart_mode = 'from_scratch'
>           outdir = '/sfiwork/dsharma/eigenvaluesSi/wf_H/'
>       pseudo_dir = '/sfiwork/dsharma/QE_Pseudos/'
>           prefix = 'H'
>          tstress = .true.
>          tprnfor = .true.
>         wf_collect =.true.
>  /
>  &SYSTEM
>         ibrav = 1
>     celldm(1) = 15
>           nat = 1
>          ntyp = 1
>       ecutwfc = 40
>       ecutrho = 160.0
>          nbnd = 2,
>          nspin=2,
>        starting_magnetization(1)=0.5
>     nosym=.true.,
>     occupations='smearing',
>     smearing='mp',
>     degauss=0.01,
>
>  /
>  &ELECTRONS
>     diagonalization ='cg'
>         mixing_mode = 'local-TF'
>            conv_thr = 1.0d-6
>         mixing_beta = 0.7
> /
> ATOMIC_SPECIES
>    H   1.00794  H.pz-vbc.UPF
>   ATOMIC_POSITIONS angstroms
>     H   0.0000  0.0000 0.0000
> K_POINTS automatic
>  1 1 1   0 0 0
>
> Thanks
>
> Dimpy
> UCC
> Ireland
>
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