[CPMD-list] VDW energy

[Ari P Seitsonen]

Dear Bairu,

   What _is_ your exact problem now?

   There are no wave function velocities after the first run because 
geometry optimisation (well, when not done via simulated annealing) does 
not produce them. You should only be concerned about this message when you 
_do_ try to restart/continue a Car-Parrinello simulation.

   Some comments about your inputs below.

     Greetings from Zurich,

        apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
   Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
   IMPMC, CNRS & Université Pierre et Marie Curie
   Tel: +33-1-4427 7542, Fax: +33-1-4427 3785, GSM: +33-6-6736 3820

On Mon, 9 Apr 2007, ÓÚ°×Èã wrote:

> Dear all cpmd-lists,
> Dear Axel,
> Thanks for your kind help. I have run again according to your suggestion,
> but the problem is still there. Why there is no wavefunction velocities in
> the restart file? Maybe something goes wrong with my input file. Could you
> please have a look at it and help me to find the problem? Thank you very
> much.
> Here is my input file:
>
> &CPMD
> OPTIMIZE GEOMETRY
> NOSE IONS MASSIVE
> 300.0 2500.0
> NOSE ELECTRONS
> 0.007 15000.0

No need for NOSE when optimising the geometry.

> ODIIS
>  5
>  MAXSTEP
>  500
> STORE
>  100
> TIMESTEP
>  4.0
> EMASS
>  700.0
> COMPRESS WRITE32
> &END

I would also add

   CONVERGENCE
    1.0E-7 1.0E-4

if you want a more accurate starting geometry for the dynamics.

>
> &DFT
> NEWCODE
> FUNCTIONAL BLYP
> GC-CUTOFF
>  1.0D-06
> &END
>
> &VDW
> VDW CORRECTION
>  1
>  C6  1 1 -19.489 4.535 3.0
> &END
>
> &SYSTEM
> SYMMETRY
>  0
> CELL
>  15.000  1.0  1.0  0.0  0.0  0.0
> CUTOFF
> 70.0
> ANGSTROM
> &END
>
> &ATOMS
> *N_MT_GIA_BLYP KLEINMAN-BYLANDER RAGGIO=1.0
>  LMAX=P LOC=P
>  4
> 7.500   5.500  6.953    1   1
> 7.500   5.500  8.047    2   1
> 6.953   9.500  7.500    3   1
> 8.047   9.500  7.500    4   1
> &END
>
> My md input file is:
>
> &CPMD
> MOLECULAR DYNAMICS
> QUENCH BO ELECTRONS
> RESTART ACCUMULATORS WAVEFUNCTION COORDINATES VELOCITIES CELL

You should better not include 'CELL' when not doing NPT dynamics (which is 
VERY delicate issue anyway). If this is your first job you should also not 
specify 'ACCUMULATORS VELOCITIES' either.

> RESTART LATEST
> TRAJECTORY XYZ

I would add 'SAMPLE' and '10' on the following line: Otherwise you'll get 
the trajectory file up-dated at each step.

> TEMPERATURE
> 50.0D0

Hmm, why do you include temperature? Do you want to obtain the free energy 
for the interaction? Please remember that the temperature in such a small 
system does not make very much sense, especially the instantaneous one. 
You might also have to consider the effects of non-adiabacity due to the 
Car-Parrinello dynamics if your interaction energies are very small, and 
you might also better check that the centre of mass does not move too much 
during the simulation (or the molecules do not rotate too quickly), as 
these small contributions might become important in a very weakly 
interacting system.

> MAXSTEP
>  500

This you certainly want to extend, probably this is just for the sake of 
testing.

> STORE
>  100

No need to store so often.

> TIMESTEP
>  4.0
> EMASS
> 700.0
> COMPRESS WRITE16

Hmm, why do you here use 'WRITE16' when above 'WRITE32'? You might already 
start losing significant accuracy, and the RESTART files are VERY small 
for this tiny system in any case.

> &END
>
> .....................................
>