[CPMD-list] WAVEFUNCTION OPTIMIZATION

[Veronique Van Speybroeck]

Dear all,

to my opinion the problem is related with the use of VANDERBILT
pseudopotentials.  I have run a test job with only one C atom.  I did this
test using once Martin Trouiller pp and once Vanderbilt pseudopotentials.
The calculation with MT pp converged quite easely.  The run with the VDB
pseudopotentials does not converge for the first 500 steps.  The energy
with the VDB pseudopotentials is not systematically decreasing f.e. :
 (K+E1+L+N+X)           TOTAL ENERGY =           -5.45500029 A.U.
 (K+E1+L+N+X)           TOTAL ENERGY =           -5.45500024 A.U.
 (K+E1+L+N+X)           TOTAL ENERGY =           -5.45498588 A.U.
 (K+E1+L+N+X)           TOTAL ENERGY =           -5.45498903 A.U.
 (K+E1+L+N+X)           TOTAL ENERGY =           -5.45499337 A.U.
 (K+E1+L+N+X)           TOTAL ENERGY =           -5.45500177 A.U.
whereas for MT pps the energy systematically decreases.  I don't know if
anybody else experienced same things

Thanks

veronique

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

On Mon, 7 Oct 2002, Jan-Willem Handgraaf wrote:

> On Monday 07 October 2002 16:27, Veronique Van Speybroeck wrote:
> > Dear all,
> >
> > I am studying a system that contains 32 atoms, among which are O, N, P, H,
> > and use therefore Vanderbilt pseudopotentials.  I'm doing now the initial
> > optimization of the wavefunction.  How many steps are common for the
> > initial wavefunction optimization.  I have already done 1500 steps still
> > the convergence is not reached.  Is this normal.  The total energy does
> > not systematically decrease.  As an illustration I give the TOTAL ENERGY
> > quantity for some of the last steps :
>
> In my experience this does not seem normal. I'm studying systems up to 262
> containing Ru, O, N, C and H. The first wavefunction optimization with ODIIS
> is usually converged within 150 steps, although automatic reinitializations
> occur. This is for Trouiller-Martins PPs. Have you checked whether the total
> energy you get is lower than the sum of the Pseudoatom Total Energies, i.e.
> is the system 'bonding'? You can also start with random wavefunctions in
> stead of the atomic wavefunctions with the keyword INITIALIZE WAVEFUNCTION
> RANDOM.
>
> Good luck,
>
> Jan-Willem
>
>
>
> --
> Jan-Willem Handgraaf
> Department of Chemical Engineering
> University of Amsterdam
> Nieuwe Achtergracht 166
> 1018 WV Amsterdam
> The Netherlands
>
> Room: C6.18
> Tel: +31-20-5256492
> Fax: +31-20-5255604
> Email: jwh at science.uva.nl
>
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