[CPMD-list] Temperature simulations

[Ari.P.Seitsonen at iki.fi]

Dear Veronique,

  Some suggestions:

 - The system is too small for Gamma point only, it might be that the
   ionic configuration is unstable; you could test this by giving the
   ions a small displacement from the equilibrium positions (by the
   way, for such crystals I find the keyword 'SCALED' very useful) and
   then relax the geometry and see, if the atoms return to the lattice
   positions. The natural solution, if the structure is indeed
   unstable, is to use a bigger cell (2x2x2, i.e. 32 atoms of each
   species)

 - You don't specify the electronic mass, the default might be
   unsuitable for this system (also the electrons heat up slowly in
   your simulation)

  Please tell if this doesn't help, then we can try something else.

    Greetings,

       apsi

PS I guess that you use the option 'MOVIE SAMPLE \n 1' only for the
  debugging, right?

> I have some problems simulating the KCL lattice at elevated temperature. 
>  First I did an optimizations on the lattice.  Next I tried to heat up 
> the crystal with the inputfile as given below.  Normally I would expect 
> only small oscillations of the atoms around their equilibrium positions, 
> due to the low temperature.  Strangely the atoms undergo very large 
> variations and I get a totally distorted system.  The temperature in the 
> ENERGIES file raises also drastically.  Can somebody tell me what I do 
> wrong?  The energies file is given in attachment.  
> When I do a MD simulations microcanonically, everything goes fine and 
> the system stays in the minimuum.
> 
> Thanks in advance
> 
> veronique
> 
> 
> &CPMD
>  RESTART LATEST WAVEFUNCTIONS
>  MOLECULAR DYNAMICS CP
>  TIMESTEP
>   5
>  MAXSTEP
>   2000
>  PRINT
>   10
>  TEMPERATURE
>   5
>  QUENCH BO
>  STRUCTURE BONDS ANGLES
>  MOVIE SAMPLE
>   1
> &END
> 
> &SYSTEM
>  ANGSTROM
>  SYMMETRY
>  1
>  CELL
>  6.3 1.0 1.0 0.0 0.0 0.0
>  CUTOFF
>  25.
> &END
> 
> &ATOMS
> *Cl_VDB_U BINARY NEWF
>  LMAX=P
>  4
>  0.000000    0.000000    0.000000
>  3.150000    0.000000    3.150000
>  0.000000    3.150000    3.150000
>  3.150000    3.150000    0.000000
> *019-K-ca-sp-vgrp.uspp BINARY NEWF
>  LMAX=P
>  4
>  3.150000    3.150000    3.150000
>  0.000000    0.000000    3.150000
>  0.000000    3.150000    0.000000
>  3.150000    0.000000    0.000000
> &END
> 
> &DFT
>  LDA CORRELATION PZ
>  FUNCTIONAL BP
>  GC-CUTOFF
>  5.D-5
> &END

-- 
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
 Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
 Tel +41 1 635 44 97 / Fax +41 1 635 68 38 / GSM +41 79 719 09 35      
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