« previous next »
Pages: [1]   Go Down

Author Topic: negative phonon in phonon band structure  (Read 4415 times)

0 Members and 1 Guest are viewing this topic.

Offline chethankumar_m

  • Regular QuantumATK user
  • **
  • Posts: 15
  • Country: in
  • Reputation: 0
    • View Profile
negative phonon in phonon band structure
« on: October 18, 2016, 09:03 »
Hello
 I have calculated phonon band structure of graphene using classical potential but, in phonon band structure ZA band near Gamma position going negative. In reported result, it is positive only. how to solve this?
Logged

Offline Petr Khomyakov

  • QuantumATK Staff
  • Supreme QuantumATK Wizard
  • *****
  • Posts: 1290
  • Country: dk
  • Reputation: 25
    • View Profile
Re: negative phonon in phonon band structure
« Reply #1 on: October 18, 2016, 10:48 »
Could you attach the python script related to this phonon calculation? Which 'reported result' do you refer to? Was this 'reported result' obtained with the same classical potential you have adopted in ATK Classical for carbon?
Logged

Offline Julian Schneider

  • QuantumATK Staff
  • QuantumATK Guru
  • *****
  • Posts: 164
  • Country: dk
  • Reputation: 25
    • View Profile
Re: negative phonon in phonon band structure
« Reply #2 on: October 18, 2016, 12:04 »
We don't know the details of your system, but have you tried optimizing the configuration before calculating the phonon band structure?
That might remove the unstable modes ( which are, at least in my case, not at gamma ).
Logged

Offline chethankumar_m

  • Regular QuantumATK user
  • **
  • Posts: 15
  • Country: in
  • Reputation: 0
    • View Profile
Re: negative phonon in phonon band structure
« Reply #3 on: October 18, 2016, 16:50 »
Thank you
Logged

Offline ams_nanolab

  • Supreme QuantumATK Wizard
  • *****
  • Posts: 389
  • Country: in
  • Reputation: 11
    • View Profile
Re: negative phonon in phonon band structure
« Reply #4 on: October 26, 2016, 18:25 »
It goes away with optimization. But keep in mind that you optimize with DFT first.
Logged

Offline quantumtoday

  • Heavy QuantumATK user
  • ***
  • Posts: 29
  • Country: fr
  • Reputation: 0
    • View Profile
Re: negative phonon in phonon band structure
« Reply #5 on: February 3, 2017, 16:28 »
it seems very hard to remove negative bands if using the potential tersoff_C_2010 (even the structure was optimized). Did you succeed in using this potential?

My concern is that is there any rule when optimizing structures to be sure that negative bands will go away just by one or two times of optimization?
Logged
Pages: [1]   Go Up
« previous next »