[Pw_forum] constraints in the ionic dynamics

[Axel Kohlmeyer]

On Tue, 13 Nov 2007, alan chen wrote:

AC> Dear PWSCF users,

dear hanghui,

AC>        I am now trying to impose some constraints in the ionic dynamics.
AC> However, after I checked the code I found that if I use 'bfgs' algorithm for
AC> 'relax' calculation, the constraints are not implemented in the code. It

implementing constraints in a geometry optimization (unlike in
an MD) is a non-trivial task. many codes i know "fake" them by
using a very, very stiff force constant. using damped dynamics
is a reasonable alternative to BFGS and will allow constraints.

ceers,
   axel.


AC> seems that contraints can only be imposed in the molecule dynamics using
AC> Verlet algorithm. Is that true? Any one can share his or her experience in
AC> imposing contraints in the ionic dynamics?
AC>       Thank you very much.
AC> 
AC> Hanghui
AC> Department of Physics
AC> Yale University
AC> 

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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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