On Sunday, March 12, 2017 11:00:58 PM CET Min Hong wrote: > Hi Lorenzo, > > Thanks for your kind response. > > Is it enough to calculate the phonon linewidth and thermal conductivity just > using the Gamma point?
Well, I cannot know. What I can tell is that the 2-body force constants (aka phonons) are probably longer range than the 3-body force constants (aka d3). You can do the phonon calculation on a fine grid (and only export fildrho at Gamma, use start_q, last_q) and then do d3 only at Gamma: the linewidth machinery does not need the ph and d3 initial grids to be equal. If your cell is large enough, samplig just the gamma point for the 3-body force constans may be enough, also thanks to periodic boundary conditions, Fourier interpolation, you already get quite a bit of information. Full disclosure: the performance advantage of perturbation theory, w.r.t a finite-difference calculation, is not evident at the Gamma point. You can still get better accuracy and you won't have to check the derivation w.r.t. the finite displacement, but you'll be limited to norm-conserving psp and non spin polarized calculations. So if you can only do the Gamma point anyway, it may be worth considering a finite difference calculation. hth -- Dr. Lorenzo Paulatto IdR @ IMPMC -- CNRS & Université Paris 6 phone: +33 (0)1 442 79822 / skype: paulatz www: http://www-int.impmc.upmc.fr/~paulatto/ mail: 23-24/423 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
