On Sat, 15 May 2010 16:21:47 +0200, xirainbow <nkxirainbow at gmail.com> wrote: > *Question one: *How to write the input file of ph.x to get phonon > dispersion along a special line.
There is a set of scripts from Eyvaz Isaev that does that, I think. They should be included in the most recent version of QE. However, the standard way to do it is compute phonons on a regular grid and then use Fourier interpolation to have a nice smooth curve along the path of your choice. See example06 for details. > *Question two:* What is the unit of q point? It is 2 pi/alat, where alat is the lattice parameter (i.e. what you specified as celldm(1), or as "a" in the pw.x calcualtion) > * Dynamical matrices for ( 4, 4, 4,) uniform grid of q-points* > * with only ( 4, 2, 2,) point requested* > * ( 1q-points):* > * N xq(1) xq(2) xq(3) * > * 1 0.50000 0.50000 0.50000 "* > * Calculation of q = 0.5000 0.5000 0.5000* > *Question three:* Why *q= 0.5 0.5 0.5?* > I think it should be *q= -0.5 0.5 0.8713185.* I think you are right, well actually it would be 0.5 -0.5 0.8713185. But I've noticed that the subroutine computing the value of the q-point is actually called *after* the one the prints it; I guess the calculation is probably done at the correct point, it is the output on screen that is wrong. At the end of the calculation you can check inside the dynamical matrix file (matdyn) to be sure. > *Question four: Is unit of q point for "ldisp = .true." and "ldisp = > .false." the same? * Yes, I think it is just the problem is the one I was stating above. > *Thanks in advance??* you're welcome, thank you for reporting -- Lorenzo Paulatto *** Note: my affiliation has changed! please send future correspondence to: <Lorenzo.Paulatto at impmc.upmc.fr> *** post-doc @ IMPMC/UPMC - Universit? Paris 6 phone: +33 (0)1 44 27 74 89 www: http://www-int.impmc.upmc.fr/~paulatto/ previously: phd student @ SISSA & DEMOCRITOS (Trieste) phone: +39 040 3787 511 www: http://people.sissa.it/~paulatto/
