[Pw_forum] questions on the acoustic sum rule crystal
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 crystalno >> 4 crystalcrystal >> >> 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
[Pw_forum] questions on the acoustic sum rule crystal
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 crystalno > 4 crystalcrystal > > 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] questions on the acoustic sum rule crystal
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' ? ! zasr : Indicates type of Acoustic Sum Rules used for the Born ! effective charges (character): ! - 'no': no Acoustic Sum Rules imposed (default) ! - 'simple': previous implementation of the asr used ! (3 translational asr imposed by correction of ! the diagonal elements of the force-constants matrix) ! - 'crystal': 3 translational asr imposed by optimized ! correction of the IFC (projection). 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 crystalno 4 crystalcrystal Should there be differences in the final DOS in the combinations 2, 3, and 4? -- Eduardo Menendez -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20080309/7863b2f0/attachment.htm
