[Pw_forum] Iron surface Molecular Dynamics

[Nicola Marzari]

Vincenzo, Giuseppe,


in principle it was meant to do Born-Oppenheimer MD - i.e.
use ensemble-DFT minimization of the electronic-structure
(a combination of conjugate-gradient and unitary rotation
minimizations), and verlet ionic steps.

In practice, I do not think it has ever been tested fully
(but it did work e.g. for large Al surfaces). Some of these missed 
minima refer to the fact that the parabolic interpolation of the energy
in the cg step predicts a minimum  that turns out not to be lower in
energy than the initial point.

Maybe we can discuss this offline with Vincenzo, and Paolo Umari?

				nicola





On 08/05/2013 17:36, Giuseppe Mattioli wrote:
>
> Dear Vincenzo
> Before discussing your setup, I note that you are using the ensemble-DFT approach implemented in cp.x. I suspect (but perhaps I may be wrong), that it
> cannot be used to propagate ions in a proper (NVT, NPT, ...) molecular dynamics simulation, but only to optimize structures through damped molecular
> dynamics. Have you tried first to optimize your system by using pw.x instead of cp.x, and some smearing scheme to deal with metallic systems? You could
> eventually consider (especially if there are no H atoms involved) a Born-Oppenheimer MD with pw.x as a good solution...
> HTH
> Giuseppe
>
> On Wednesday 08 May 2013 16:00:01 Vincenzo Verdolino wrote:
>> Dear all,
>>
>> I am dealing with Iron surface catalyst and I'm trying to run MD simulation
>> with cp.x
>>

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Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL