[Pw_forum] Re: CP for metals

[Konstantin Kudin]

 Hi Paul,

 It is good to see you chime in on the issue!

--- Paul Tangney <tangney at civet.berkeley.edu> wrote:


>  > The main issue is that there is usually some "natural" fictitious
>  >kinetic energy that electrons gain from the ionic motion ("drag").
> One
>  >could easily quantify how much of the fictitious energy comes from
> this
>  >drag by doing a CP run, then a couple of CG (same as BO) steps, and
>  >then going back to CP. The fictitious electronic energy at the last
> CP
>  >restart will be purely due to the drag effect.
> 
> I'm not sure I understand precisely what you are proposing here, but
> if you are proposing to restart CP with finite ionic velocities
> and stationary orbitals, you will give the orbitals a "kick" that 
> substantially increases their fictitious kinetic energy (FKE) above
> the 
> amount that is purely due to drag. (See the review by Remler and
> Madden
> or Tangney,Scandolo JCP  116, 14 2002)

 I am proposing to restart CP with finite ionic velocities and MOVING
orbitals. This is achieved by doing a couple of BO (CG) steps for
moving ions, with the fully converged wavefunctions for the last 2
steps saved. This way CP will be restarted from the BO wavefunctions
which were moving with the ions and thus contain the full drag effect
(and only the drag effect!).
 
 I think this is identical to restarting CP with both ionic and
wavefunction velocities set to zero, only now they can be finite.

 This CP->CG->CP smooth restart functionality is already in Espresso
3.0.

 Kostya



	
		
__________________________________ 
Yahoo! Mail - PC Magazine Editors' Choice 2005 
http://mail.yahoo.com