Dear Hanghui: I think this is just because of periodic boundary conditions. Thinking in 1D, as always, helps. Suppose you have a cell of size L. You place one atom, say A, at the origin (x=0), and another one, say B, at x=2/3 L. What will be the distance between A and B? Not 2/3 L, but L/3!
Hope this helps Stefano Baroni On Nov 9, 2007, at 4:02 AM, alan chen wrote: > To whom it may concern, > I am trying the CONSTRAINTS card for ionic dynamics. One of > the 'constr_type' is 'distance'. However, if the distance of the > two atoms I want to fix is larger than 'dmax' (dmax is half the > shortest edge of the cell), the code crashes. > I would like to ask why we can not fix two atoms whose > distance is NOT larger than 'dmax'? Does the algorithm not work > well if the distance of two atoms to be fixed is too large? > Thank you very much. > > Hanghui > > Department of Physics, > > Yale University > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20071109/e12379a0/attachment-0001.htm
