[CPMD-list] Energy conservation

[Juerg Hutter]

Hi Nick

the problem with energy conservation with systems of this
type is often related to the thermostats.
Instead of reducing the timestep you should try to
increase the order of the integrator and the
decomposition ratio for the thermostats.
You do this by setting

NOSE PARAMETERS
 4 4 4 6  125 4

other choices for the Suzuki integrator are
3,5,7,9,15,25,125,625

The decomposition ratio is by default 1 (last number)
and I did set it to 4. I don't have too much experience
with that.

regards

Juerg

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 1 635 4491
Physical Chemistry Institute   FAX   : ++41 1 635 6838
University of Zurich           E-mail: hutter at pci.unizh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
----------------------------------------------------------


On Wed, 15 Oct 2003, Nick Cooper wrote:

> Hello all,
>
> I am simulating covalent materials at relatively high temperatures (3500K)
> and I have noticed that the conserved quantity in a canonical ensemble is
> monotonically decreasing, though admittedly the absolute change is small.
> I have tried decreasing the timestep (from 3au down to 1au) but all this
> does is decrease the gradient of the drop in energy. The systems I am
> looking at have significant metallic character at this temperature, so I
> have used a Nose-Hoover themostat for the ions and wavefunctions.
>
> The monotonic nature is what has me worried- am I just being paranoid?
>
> Any advice you can offer would be gratefully received.
>
> Yours sincerely,
>
> Nicholas Cooper
>
> PhD Student,
> The University of Sydney,
> NSW 2006 AUSTRALIA
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