[Pw_forum] Is there a large difference between vc-relax calculation using "damp", "damp-w" and "bfgs", "bfgs" algorithm

[Stefano Baroni]

too short a time step?
SB

On Dec 5, 2009, at 4:37 AM, mohnish pandey wrote:

> Dear users !
>                     I tried to calculate bulk energy and equilibrium lattice parameters of some system using vc-relax calculation. I done the calculation using both the algorithm naming (1)damped dynamics means 'ion_dynamics' as "damp" and 'cell_dynamics' as "damp-w" (2) BFGS means 'ion_dynamics' as "bfgs" and 'cell_dynamics' as"bfgs" .  I have changed only these two things in these two alogorithm. But first case was taking very much time(~2hours) and wasnt convergence after 200 ionic steps whereas in the second case it took very less time (6-7 minutes) to get equilbrium bulk structure. Can anybody please explain me what is the thing which is making so much differnce?
> Sincere thanks in advance,
> Mohnish
> 
> -- 
> Mohnish Pandey
> Y6262,4th Year Undergraduate,
> Department of Chemical Engineering,
> IIT KANPUR
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
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