On Dec 25, 2008, at 5:30 PM, Reza Ebraahimi wrote: > Hi
Hi > can anyone refer me to some literature about history of acoustic sum > rules? i mean when was it proposed for the first time? Pick, Cohen, Martin, Phys. Rev. B 1, 910 - 920 (1970) > and it's versions known here as "simple" and "crystal"? "simple" only deals with q->0 frequencies, and modifies the q=0 dynamical matrix so as to impose that the sum of the eigenvalues vanishes (this can be achieved by subtracting T/N from the diagonal elements, where T is the trace and N the dimension); "crystal" would do something more sophisticated on the interatomic force constants, so as to enforce continuity in the q->0 limit. do not know if the details have ever been written anywhere > Thank You you are most welcome. you would be even more so if you took the time of signing your posts to this forum, including your accademic affiliation. Best wishes Stefano Baroni --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget 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/20081225/9ff20d68/attachment.htm
