Dear Nicola, Thanks for your kind explanation. I will use the working version from the cvs and the new release of the code.
Best regards, hiroshi - Department of Earth & Planetary Sciences Graduate School of Science & Engineering Tokyo Institute of Technology 2-12-1 Ookayama Meguro-ku Tokyo 1528551 Kawamura Lab. Tel: +81-3-5734-2617 Nicola wrote: >Dear Hiroshi, >thanks again for your observations - it turns out that in recent times >(years) a small modification had arisen in the way the center of mass >is treated that gave rise (in the very exotic case that you have been >looking at) to the observed behavior. Roberto Car and his group >(Federico Zipoli and Zhaofeng Li) has also noticed this a few months >ago, but it has percolated back into the code just now. >You can download the working version from the cvs, with these two >commands: >cvs -d :pserver:anonymous at scm.qe-forge.org ><http://www.democritos.it/mailman/listinfo/pw_forum>:/cvsroot/q-e login >cvs -d :pserver:anonymous at scm.qe-forge.org ><http://www.democritos.it/mailman/listinfo/pw_forum>:/cvsroot/q-e checkout >>espresso >or wait for a few days for the new release of the code, coinciding >with the Santa Barbara school. >If you apply it to your example, you'll notice that the constant >of motion of the CP lagrangian is perfectly conserved, the physical >constant of motion is very well conserved (as it should be), and also >that after a fraction of a ps the water molecule will take up some >kinetic energy (average around 10K, i.e. osciallting between 0 and 20K) >due to the transfer of momentum between the fictitious system and the >physical one. This is normal, and the relatively large amount is due to >this very unusual case, using on top a lot of plane waves. It would be >negligible in any large system. >All the best, > nicola
