How does resolve negative frequency and positive energy problem in phonon calculation (IBRION=8) DFPT by VASP ?

Shilendra Kumar Sharma @Shilendra-Sharma

02 February 2017 3 2K Report

Hi All

I am doing phonon calculation of adsorbate surface using supercell DFPT (IBRION=8) method. During completion of total degree of freedom 192,

after 133/192 degree of freedom energy is going to be positive like

Linear response progress:

Degree of freedom: 133/192

N E dE d eps ncg

rms rms(c)

RMM: 1 0.217378571184E+00 0.21738E+00 0.19116E+02 5386

0.343E+01

RMM: 2 0.127254148439E+00 -0.90124E-01 -0.55512E-02 8094

0.438E-01 0.322E-01

RMM: 3 0.124590051032E+00 -0.26641E-02 -0.16976E-02 11623

0.162E-01 0.602E-01

RMM: 4 0.125935957234E+00 0.13459E-02 -0.39499E-03 8126

0.103E-01 0.490E-01

RMM: 5 0.123635491638E+00 -0.23005E-02 -0.39546E-03 9713

0.765E-02 0.601E-01

RMM: 6 0.121118955639E+00 -0.25165E-02 -0.38393E-03 9767

0.453E-02 0.743E-01

RMM: 7 0.125200747539E+00 0.40818E-02 -0.44584E-03 8647

0.634E-02 0.253E-01

RMM: 8 0.127131220393E+00 0.19305E-02 -0.45986E-04 7966

0.449E-02 0.186E-01

RMM: 9 0.127249394402E+00 0.11817E-03 -0.23046E-04 8953

0.247E-02 0.142E-01

RMM: 10 0.127427043358E+00 0.17765E-03 -0.40435E-05 8644

0.178E-02 0.379E-02

RMM: 11 0.127451795033E+00 0.24752E-04 -0.11972E-05 9286

0.922E-03 0.425E-02

RMM: 12 0.127439216517E+00 -0.12579E-04 0.95608E-06 7792

0.606E-03 0.138E-02

RMM: 13 0.127433858265E+00 -0.53583E-05 0.11061E-05 9347

0.344E-03 0.164E-02

RMM: 14 0.127440025812E+00 0.61675E-05 0.14637E-05 8767

0.248E-03 0.474E-03

RMM: 15 0.127441655698E+00 0.16299E-05 0.16395E-05 9768

0.141E-03 0.593E-03

RMM: 16 0.127442586932E+00 0.93123E-06 0.15813E-05 9059

0.981E-04 0.249E-03

RMM: 17 0.127444457475E+00 0.18705E-05 0.14892E-05 10340

0.592E-04 0.202E-03

Why is this so ? How to resolve this problem ?

For My other bulk system 2*2*1 supercell (96 atoms)I am getting negative

frequecies. I read it shows instability of system at 0K. If after possible

improvement in calculation negative frequencies still remains then what

should we do for confirming instability of system at 0K. Does people

report negative frequencies in phonon DOS ?

How does resolve negative frequencies? I have attached here my phonon DOS.

Thank You All

Shilendra Kumar Sharma

Dear Behnam Farid, thank you for your suggestions,

I will go through these references .

Shilendra

Dear Behnam Farid ,

I did phonon calculation by DFT using VASP and I am getting negative frequencies as I posted above.

As you suggested 3 reasons for the same, among 3 reasons second one is more probable and you suggested to do abinitio MD for phonon calculation.

My query is that what will be the difference in result of phonon calculation by abinitio-MD in comparison to phonon calculation by DFT.

Both results will be difference and why ?

Thank You

Rasoul Kh

Hello everyone,

Phonon calculations (Phonon Band Structures, Phonon DOS, and thermal properties) in materials science using VASP and phonopy are explained on the Youtube Channel. Please find the link below:

https://bit.ly/2UtvbHE

https://www.youtube.com/watch?v=FX7WjL074g4

Best regards,

Rasoul Khaledialidusti

Which type of compound does lamda max of 218 indicate in a uv-vis spectrum of a partially purified compound through column and TLC?

How does grain and grain boundary affect the ceramic when studying its dielectric properties?

Reason for discontinuities in my Band structure?

If my gene of interest has high GC content can it be problematic in sequencing? What kind of error is expected with GC rich gene sequences??

How to dispose off lipids waste?

What publications should I target as a psychology masters student in the UK?

How effective has the United Nations been in addressing the conflict and its consequences?

What are the main obstacles to achieving a ceasefire or peace agreement between Russia and Ukraine?

How to decide whether the refinement is correct or not, based on Rwp and Rexp factors by Fullprof?

How to draw photon-magnon coupling color plot in origin?

VASP recognize my insulating alloy structure as not insulating?

Is it possible to plot the atom-projected band structure using GPAW?

How to use Density Functional Theory to calculate carrier mobilities of solid system?

How to build a heterostructure of two materials having different space group?

How can I use DFT-D3 correction ( Siesta version 5.0.1)?

Reason for discontinuities in my Band structure?

Why Orca calculations take too loong?

MDCI module in Orca software?

How can I calculate spin texture using Quantum Espresso for non-colinear case ?

Is it possible to run the AIMD within a system using virtual crystal approximation (VCA)?