Hi Yujia Yang, There has been a long discussion previously on the same problem. Please go through the following mail archive link:
http://www.mail-archive.com/[email protected]/msg01674.html Cheers, Juzar Thingna Department of Physics, Center for Computation Science and Engineering, National University of Singapore. "I almost wish I hadn't gone down the rabbit-hole ---and yet---and yet--- it's rather curious you know, this sort of life!" Alice On Thu, Sep 16, 2010 at 11:28 AM, Yujia Yang <[email protected]> wrote: > Hello Everyone > > I'm currently using VIBRA package to calculate phonon dispersion > relationship of graphene. But the results showed negative phonon > frequencies. Also I found the "graf" examples given by VIBRA also generated > negative phonon frequency of graphene. How can I solve this problem? > > The attached files are my input .fdf files for SIESTA and Vibrator, and the > figure of the results. > > Thanks. >
