Thanks, but this is from experiments, right? We should compare to results
from the same potentials we used...
I remember Ju Li has a paper on SiC around 1997 using a Tersoff. How about
Vashishta, any published results?
Zheyong
Florencia Carusela <flor.caru@xxxxxxxxx> 于 2019年10月17日周四 12:17写道：
Zheyong
Here is the link of the paper
https://pdfs.semanticscholar.org/de76/00d61ffc13c4cf94b973e7785ddc6a21a9bb.pdf
Thanks!
Florencia
On Thu, Oct 17, 2019 at 5:29 AM Bruce Fan <brucenju@xxxxxxxxx> wrote:
Florencia,
Thanks for the question. This seems to be a difficult question. I have
not tested the phonon code with SiC before. I tried to find the paper you
referred to, but couldn't find it. Could you give me a link to the paper?
I have a few comments after a quick look at your inputs:
1) run.in is not needed to run the phonon code. It was my fault to put
it in the released example. That was used when I developed the code. Now
you only need the following files: phonon.in, kpoints.in, basis.in, and
xyz.in. Of course, including run.in in the input directory will not
cause any problem.
2) Your create_xyz.m Matlab script will produce an xyz.in file with the
first line looking like:
512 4 3 0 0 0 0
This means that you set the cutoff distance for neighbor list building to
3 A, which is too short for the Vashishta potential.
I remember the cutoff distance for this potential is 7.35 A. Then you can
set it as 8 A. So the
first line can be changed to
512 300 8 0 0 0 0
Here, "300" is used to reserve enough memory of the neighbor list. I know
this number is difficult to choose, but I still leave it to the user rather
than using a fixed large number such as 1000. Sometimes, 4 or even 3 is
enough and one can save memory by choosing it properly.
3) Accordingly, the cutoff in phonon.in should also be changed to a
larger number, say 8 A.
4) The k-path I provided in the example might not be the same as those
used in the references you were looking for. I need to study this in more
detail.
Zheyong
On Thu, Oct 17, 2019 at 12:20 AM Florencia Carusela <flor.caru@xxxxxxxxx>
wrote:
Hi Zheyong
I have problems to calculate the phonon bands of the 3C SiC. I am using
Vashishta potential. I checked your parameters and are ok according to
Vashishta's paper.
There are problems with the optical band, I cannot reproduce it (look
e.g. APPLIED PHYSICS LETTERSVOLUME 80, NUMBER 2310 JUNE 2002).
I tried different orientations and cutt off distances but still not
working. I don't know if I am doing something wrong or something I should
tune in the code. Did you ever try to calculate it?
By the way, the phonon bands for Si with Tersoff are ok! I also tried
Tersoff with 3C SiC but it is also worse.
I attach the input files
Florencia
