[Pw_forum] Phonon dos and dispersion calculation problem.

[Stefano de Gironcoli]

this message means that the dynamical matrix is not hermitian as it 
should...
it may be due to poor self-consistent convergence in the phonon calculation
this may also be the reason for the negative (imaginary) frequencies you 
get.
try to tighten the  tr2_ph threshold.
stefano

Zhen Huang wrote:
> Dear friends,
>
> I am running a single-wall carbon nanotube case (5,0). The result of phdos shows  
> Max |d(i,j)-d*(j,i)|/|d(i,j)|: 210.0909%
>      Max |d(i,j)-d*(j,i)| =  0.062230
>      Max |d(i,j)-d*(j,i)|/|d(i,j)|: 266.6923%
>      Max |d(i,j)-d*(j,i)| =  0.062230
>      Max |d(i,j)-d*(j,i)|/|d(i,j)|: 253.1387%
>      Max |d(i,j)-d*(j,i)| =  0.062230
>      Max |d(i,j)-d*(j,i)|/|d(i,j)|: 233.9506%
>      Max |d(i,j)-d*(j,i)| =  0.062230
>      Max |d(i,j)-d*(j,i)|/|d(i,j)|: 208.3492%
>      Max |d(i,j)-d*(j,i)| =  0.062230
>      Max |d(i,j)-d*(j,i)|/|d(i,j)|: 213.2651%
>      Max |d(i,j)-d*(j,i)| =  0.062230
>      Max |d(i,j)-d*(j,i)|/|d(i,j)|: 256.8845%
>      Max |d(i,j)-d*(j,i)| =  0.062230
>
> Does any one know what is wrong with it?
>
> On the other hand, I used C.pz-rrkjus.UPF for PP. It works well with graphite
> and give reasonable dispersion. However, there are several negative value in
> nanotube results. I use 1,1,40 in relax calculation and nq=1,1,32 for ph.x
> calculation.
>  
> ---------------
> Zhen Huang
> Ph.D. Student
> Nanoscale Transport Research Group
> School of Mechanical Engineering
> Purdue University 
> Tel: 765 426 9302
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