# [Pw_forum] Phonon dos and dispersion calculation problem.

Zhen Huang huang87 at purdue.edu
Fri Aug 8 15:10:19 CEST 2008

```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

```