[Pw_forum] Binding Energy for H2O with PAW

[庞瑞(PANG Rui)]

Dear Felix
If I am correct, PBE contains self-interaction error, that means it may give a wrong number when you use it to calculate a single electron system such as hydrogen. Mayben you could try B3LYP or HSE.
Best wishes






------------------


庞瑞(PANG Rui)



South University of Science and Technology of China/Department of Physics

No.1088,Xueyuan Road, Shenzhen,Guangdong







 
 
 
------------------ Original ------------------
From:  "Felix Brockherde"<fbrockherde at gmail.com>;
Date:  Fri, Feb 26, 2016 09:31 PM
To:  "Pw_forum"<Pw_forum at pwscf.org>; 

Subject:  [Pw_forum] Binding Energy for H2O with PAW

 
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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