[CPMD-list] Re: two questions about MD

[qfzhang]

Hi,professor
  Thanks for the reply! I still have some question about the constraint force.
  Do you mean that the constrain force of one particular distance difference is 
just the average of the trajectory, and the barrier can be calculated just by in
tegrating such 'averages'?
  Another problem is that the constraint forces in the CONSTRAINT file vary heav
ily along the trajectory. Is there some method to solve such a problem? Generall
y speaking,how many timestep should be done to get the converged constraint forc
e? 
  From the example given in cpmd tutorial, when specifing CONSTRAINTS, there is 
no NOSE keyword, should that be needed in the constant temperature simulation?
   best wishes 
                                                       Zhang Qianfan
                                                        2007-02-25

Alessandro Curioni д:

> Zhang,
> 
> 
> please use  diagonalization and SCF  for the wfn optimization   ( i.e. add 
> LANCZOS DIAGONALIZATION)  when using KPOINTS -
> there is a known bug in 3.11.1 for direct optimization (e.g. PCG) and 
> k-points. This will be corrected in the new update soon to be for 
> distribution.
> Regarding the forces  on the costraint : in the file  CONSTRAINTS you have 
> the trajectory of the constraint force .....
> 
> 
> 
> Alessandro
> 
> Alessandro CURIONI, PhD
> Research Staff Member
> Computational Biochemistry and Material Science group
> IBM Research Division - Zurich Research Laboratory
> Saumerstrasse 4
> 8003 Rueschlikon - Switzerland
> e-mail: cur at zurich.ibm.com
> www:    www.zurich.ibm.com
> Tel: +41-1-7248633
> Fax: +41-1-7248958
> 
> 
> 
> 
> "qfzhang" <qfzhang at aphy.iphy.ac.cn> 
> Sent by: cpmd-list-bounces at cpmd.org
> 02/23/2007 10:22 AM
> 
> To
> cpmd-list at cpmd.org
> cc
> 
> Subject
> [CPMD-list] two questions about MD
> 
> 
> 
> 
> 
> 
> Hi,expert!
>    This is my first time to send email to this mailing list. I have two 
> question
> s in MD.
>    The first one is about BOMD.I want to use k points to simulate the 
> crystal sy
> stem. but when I specified the keyword MOLECULAR DYNAMICS BO in $CPMD, and 
> used 
> KPOINTS MONKHORST-PACK, I find that the electronic energy in the loop of 
> \\'force 
> initialization\\' can never converge.I don\\'t know why. Must I specified some
 
> speci
> al keywords in the input file?
>   The second is about the output file CONSTRAINTS. when I get the 
> CONSTRAINTS fi
> le. How can I get the constraint force? I have fixed the structure of 
> distance d
> ifference--DIFFER.
> 
> 
>    best wishes
>                                                    Qianfan Zhang
>                                                     2007-02-23
> 
> 
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