[Pw_forum] Binding Energy for H2O with PAW

[Jess Wellendorff]

Dear Felix.

Is "binding energy" the same as (negative) "atomization energy" in this 
context? Should be quite possible with PAWs.

Regards,
Jess

On 02/26/2016 02:31 PM, Felix Brockherde wrote:
> Dear all,
>
> We would like to calculate the binding energy for non-equilibrium H2O 
> geometries with PAW pseudo potentials.
>
> The initial thought was to calculate the single-atom energies. 
> However, for H the system becomes metallic. We used smearing but the 
> results seem too far from the experimental value for us to use them 
> (-0.91784682 Ry).
>
> Now, we would like to calculate the binding energy by separating the 
> H2O molecule as far as necessary. We would thus avoid inaccuracies 
> caused by smearing because it is not a metallic system. However, when 
> pulling H2O apart, the DFT calculations do not converge.
>
> Can anybody help with either how to get the separated H2O converged or 
> a different approach to get the binding energy with PAW pseudo potentials?
>
> We used PWSCF v.5.1.1 and I attached an input file where QE does not 
> converge.
>
> Best regards,
> Felix Brockherde
> TU Berlin
>
>  &CONTROL
>     calculation = 'scf',
>     wfcdir = 'tmp',
>     pseudo_dir = '/home/user/pseudo_potentials',
>     tprnfor = .true.,
>     prefix = 'prefix',
>     tstress = .false.,
>     outdir = './',
>     wf_collect = .true.,
>  /
>  &SYSTEM
>     nat = 3,
>     ntyp = 2,
>     ecutwfc = 90,
>     ecutrho = 360,
>     celldm(1) = 30,
>     ibrav = 1,
>  /
>  &ELECTRONS
>  /
> ATOMIC_SPECIES
>     H 1.00794 H_pbe-kjpaw_psl.0.1.UPF
>     O 15.9994 O_pbe-kjpaw_psl.0.1.UPF
> ATOMIC_POSITIONS alat
>     O 0.5 0.3 0.5
>     H 0.5 0.7 0.3
>     H 0.5 0.7 0.7
> K_POINTS automatic
>    1 1 1   0 0 0
>
>
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