Hi Eduardo, If you are interested in learning more about the Lagrangian approach for the acoustic sum rule, the full reference for the paper is:
N. Mingo, D. A. Stewart, D. A. Broido, and D. Srivastava, ?Phonon transmission through defects in nanotubes from first principles?, Physical Review B 77, 033418 (2008) I also have a local copy of it stored on my webpage. http://www.people.cornell.edu/pages/das248/ We developed this approach while working on some thermal transport calculations for nanotubes using real space force constants from the Siesta code. It should be able to handle fairly large systems. I think the largest we have used it on so far is a 7 unit cell (6,0) nanotube. Best regards, Derek Nicola Marzari writes: > Eduardo Ariel Menendez Proupin wrote: >> Hi, >> >> Question 1. This question is about the Acoustic Sum Rule in phonon >> calculations. Is there a reference to learn about the option >> zasr='crystal'? >> Is 'crystal' always better than 'simple' ? > > > I think "crystal" was implemented by Nicolas Mounet - a MSc student here > in our group - and was based on the idea that the IFCs are a vector in > a multi-dimensional space, and you should take the projection of these > onto the hypersurface where the ASR are satisfied. I'd think it's > better, in that it imposed simultaneously all constraints in the > least disruptive way, if oyu are happy with the cartesian metrics > for the distance; it might take a lot of memory or time in really large > systems. > > It's described in his thesis - I'd be happy to send it. We never > published it, but maybe it's time - a recent PRB by Mingo also discusses > it, and introduces another alternative based on Lagrangian multipliers. >> >> Question 2. Consider the calculation of the phonon DOS, as in example >> 06. The ASR can be imposed in the run of q2r and/or in the run of >> matdyn, let's say >> There are four combinations of zasr-asr in q2r an matdyn >> q2r matdyn >> 1 no no >> 2 no crystal >> 3 crystal no >> 4 crystal crystal >> >> Should there be differences in the final DOS in the combinations 2, 3, >> and 4? > > I'd like to know myself -but last time I looked into the q2r and > maydyn was 16 years ago :-( . Maybe you could report any differences > (rather than in the DOS, I'd look at low energy acoustic phonons, both > at Gamma but especially close to gamma, but not really there). > > nicola > > > --------------------------------------------------------------------- > Prof Nicola Marzari Department of Materials Science and Engineering > 13-5066 MIT 77 Massachusetts Avenue Cambridge MA 02139-4307 USA > tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > ################################ Derek Stewart, Ph. D. Scientific Computation Associate 250 Duffield Hall Cornell Nanoscale Facility (CNF) Ithaca, NY 14853 stewart (at) cnf.cornell.edu (607) 255-2856
