[Pw_forum] About relaxation and cpmd

[Manoj Warrier]

Well .. you can do a MD to relax, but you cannot do a "relax" to
simulate dynamics :-).

Seriously speaking .. relaxing a group of atoms will be to get the
configuration of the atoms that have the lowest total energy. This can
be done by various simulation methods like: (i) Method of conjugate
gradients, (ii) Simulated Annealing, (iii) Genetic Algorithms, (iv) ??
Notes for these are available online at
http://beam.acclab.helsinki.fi/~knordlun/mc/ and a google (scholar)
search will lead to applications with examples.

In MD, relaxing a group of atoms involves using a NPT ensemble to get
the system to oscillate around zero pressure at temperature T by
changing the volume of the system. Simulated annealing or Genetic
Algorithm can usually take your atoms to a more global relaxed state
than your MD will.

Wondering what the experts' take will be on the above ...

Best Regards,
Manoj Warrier
Institute for Plasma Research,
BHAT, Gandhinagar, Gujarat,
India - 382428

On 25/12/2007, oulihui666 <oulihui666 at 126.com> wrote:
> Dear all,
>     I have a naive problem, and need your help. I have not understanded this
> problem
> for a long time, etc. the difference between relaxation and molecular
> dynamics(cpmd), I
> think that there is many steps in the process of relaxation, and every step
> denotes
> a intermediate, however, It also contains many intermediate in molecular
> dynamics
> simulation, I do not understand the difference between relxation and
> molecular
> dynamics(cpmd) at all times. Anyone who would give suggestion will be
> appreciated.
>     Thanks in advance
>     Lihui Ou
>
>
> --
>
>
> ======================================
> Lihui Ou
> PH.D Candidate in Electrochemistry
> College of Chemistry and Molecular Science
> Wuhan University,430072,Hubei Province,China
> E-mail:oulihui666 at 126.com
> ======================================
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-- 
Manoj Warrier
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And everything should be possible with the
click of a mouse in my perfect world!!
-Lord Farquad
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http://www.ipr.res.in/~manoj