[Pw_forum] problem with the geometry optimization of cp.x

[Giuseppe Mattioli]

Dear Alex
Have you tried to run the same geometry optimization with pw.x and/or with different pseudopotentials (there is plenty of C,N,O,H PPs...)? Do they come 
out with the same results? Or have you simply found a new, very smart water splitting catalyst? :-)

>   ibrav = 1, 
>   celldm(1) = 20, 
>   celldm(2) = 0.0, 
>   celldm(3) = 0.0, 
>   celldm(4) = 0.0, 
>   celldm(5) = 0.0, 
>   celldm(6) = 0.0, 

It should not matter, but you need only

>   ibrav = 1, 
>   celldm(1) = 20.0,

Remember that celldm(2) is not "b" (if celldm(1)="a" in an orthorhombic cell), but b/a. Thus, you are saying to the code that b=0... 

I do not see any other reason related to the calculation setup which could explain anomalous results. Check again your starting structure (or attach 
your whole input file in a further mail if you look again for some help...)

HTH

Giuseppe

On Thursday 28 November 2013 14:43:50 Alex wrote:
> Dear user QE.
> 
> I'm using cp.x to perform molecular dynamics of one of bulk water molecules
> with asparagine. Following protocol, I minimized the function of wave
> electronics with stationary nuclei.
> 
> However, in the second stage, during the optimization of the geometry (with
> damp for electrons and ions)  the water molecules take a non-real
> geometry, in which one side of the molecule, the OH distance becomes 1.98
> angstrorn (A). The opposite side, has the normal size of the bond which is
> 0.97 A. I confess that since I started using it very often, and sometimes
> does not, but do not know why that. Sometimes change is functional and
> that resolved, sometimes not.
> 
> 
> 
> Incoherent bond distances of water after geometry optmization  >>>>>  
> H------------------O -----------H (sorry by bad graphic)                  
>                                                                | 1.98 A|  
>     |0.97 A|
> 
> 
> Can someone help me? 
> Put my input to be analyzed.
> 
> 
> &CONTROL
>   title = 'Asp0s'
>   calculation = 'cp',
>   restart_mode = 'restart',
>   ndr = 51      !already minimized wf with sd for electrons and ions=none.
>   ndw = 52, 
>   nstep  = 50000,
>   iprint = 1, 
>   isave  = 10,
>   tstress = .TRUE.,
>   tprnfor = .TRUE.,
>   dt    = 5.0d0,
>   etot_conv_thr = 1.d-8,
>   ekin_conv_thr = 1.d-4,
>   forc_conv_thr = 1.d-4,
>   prefix = 'asp'
>   pseudo_dir = 'pseudo/'
>   outdir = './'
> /
> 
> &SYSTEM
>   ibrav = 1, 
>   celldm(1) = 20, 
>   celldm(2) = 0.0, 
>   celldm(3) = 0.0, 
>   celldm(4) = 0.0, 
>   celldm(5) = 0.0, 
>   celldm(6) = 0.0, 
>   nat  = 122,
>   ntyp = 4,
>   ecutwfc = 70.0,
> /
> 
> &ELECTRONS
>   emass = 400.d0,
>   emass_cutoff = 2.5d0,
>   orthogonalization = 'ortho',
>   electron_dynamics = 'damp',
>   electron_damping = 0.1
>   ortho_max = 500,
>   !electron_temperature = 'not_controlled',
>   !electron_velocities = 'zero'
> /
> 
> &IONS
>   ion_dynamics = 'damp',
>   ion_damping = 0.01,
>   !ion_nstepe = 10,
>   !ion_temperature = 'nose',
>   !tempw = 350,
>   !fnosep = 70,
>   !ion_velocities = 'zero'
> /
> 
> 
> ATOMIC_SPECIES
> 
>  O 16.0d0  O.pbe-hgh.UPF
>  H 1.0d0   H.pbe-hgh.UPF 
>  C 12.0d0  C.pbe-hgh.UPF 
>  N 14.0d0  N.pbe-hgh.UPF
> 
> ATOMIC_POSITIONS {angstrom}
> 
>    C     -0.244144     1.783022    -1.335832 
>    C     -2.567204    -0.241389     5.783803 
>    N     -1.038197    -1.652589     5.418683 
>    C     -6.336078    -1.532299    -1.532562 
>    O     -5.122808    -0.424258    -2.279843 
>    N      3.987336     0.412822    -1.692063 
>    C      0.552282    -0.043486     0.368085 
>    O      1.73575      0.043368     0.476670 
>    O      1.126133    -1.181319     1.757325 
>    H     -0.844512    -1.781630    -0.580034 
>    H     -1.992345    -1.968023     0.581635 
>    H     -1.547999    -0.018973     1.618910 
>    H     -1.017864     1.793541     0.067225 
>    H     -2.180408     0.669590    -0.675764 
>    H      1.490782     1.185685    -2.387313 
>    H      1.070763     1.992771    -0.909308 
>    H      0.490233    -1.888235     1.458829 
>    O      5.160929     1.400891    -4.018523 
>    H      5.585303     1.845186    -4.767840 
>    H      5.903707     1.074826    -3.488501 
>    O      6.523016    -2.630620    -1.333026 
>    H      6.731773    -1.730291    -1.624223 
>    H      6.238875    -2.519196    -0.413345 
> ( ........)
> 
> 
> Alex.
> Thanks to all.


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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
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