[Pw_forum] questions on the acoustic sum rule crystal
stewart at cnf.cornell.edu
stewart at cnf.cornell.edu
Mon Mar 10 14:47:46 CET 2008
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
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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
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