Dear Salbadu: I am sure this has been explained many, many time on this forum, and I would like to invite you to search old posts. In a nutshell, mathematically allows to turn the integration of a discontinuous function (the T=0 Fermi distribution) into that of a continuous function; physically, degauss can be seen as a kind of fictitious temperature (the Fermi distribution is continuous at T=/= 0), and some of the tricks that are used in conjuction with Gaussian spearing (e.g. for the calculation of Hellmann-Feynman forces) actually take advantage from this physical analogy. If you want to know/understand more _after_ your browse the past posts in this form and read some of the relevant literature, please revert to us. Stefano Baroni
On Sep 7, 2009, at 8:35 AM, udayagiri sai babu wrote: > Dear all > can somebody tell me how to choose a correct degauss value for an > SCF calculation and also the physics behind it. > > -- > U.Saibabu > PhD student, > Deformation mechanisms modeling group, > Materials engineering department, > IISc Bangalore, > India. > > _______________________________________________ > 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 http://stefano.baroni.me [+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/20090907/6a8e4c48/attachment.htm
