Questions tagged [phonon-dispersion]

Questions relating to phonon dispersions - the relationship between the phonon frequency and its wave vector.

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Why dipole correction does not work in VASP DFPT + phonopy calculation for a stable 2D material

Seems that DFPT method in VASP has many defects. It can't include vdw interaction. Now I found it also can't include dipole correction, which leads to a large negative frequency at $\Gamma$ point. I ...
mollen's user avatar
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2 votes
1 answer
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Question regarding q2r in QuantumEspresso Phonon Calculation

Let's suppose I've already run an scf calculation for an input file. Now I can read the wave functions and with ph.x I can get the dynamical matrices. I'll get as many files as the number of q-points ...
CoolerThanACooler's user avatar
2 votes
0 answers
89 views

LO-TO Splitting and Group Theory

I am curious whether or not there is a connection between the group theoretical assignment of phonon modes and LO-TO splitting. For example, is it true that the frequency of a gerade mode will depend ...
CW279's user avatar
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5 votes
1 answer
218 views

Can you calculate fat ("projected") phonon dispersion bands with Quantum Espresso?

I would like to calculate the fat phonon bands for a chosen material (for simplicity, suppose GaAs), similarily as in Fig. 3 of reference [1]: This is effectively the analogue of projected band ...
Neinstein's user avatar
  • 283
5 votes
1 answer
159 views

project molecular dynamics trajectory onto phonons by normal mode decomposition

After running the Molecular dynamics(MD) simulation, I'd like to see the excitation of phonons during MD, so I'd like to project the trajectory onto a set of phonons, I've seen some paper use the ...
Jack's user avatar
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5 votes
1 answer
165 views

Getting the Phonon Dispersion Using fix phonon in LAMMPS

I am using fix phonon in LAMMPS to get the phonon dispersion relation, but this requires a post-processing code that takes the generated binary file and produces ...
Mohamed's user avatar
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5 votes
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221 views

Electron-phonon coupling plotted as function of phonon bands [closed]

I'm looking to superimpose electron phonon coupling (EPC) constants per phonon band per k-point as is done in Figures 6c and 6d in this paper, essentially a "fat band" plot where the ...
user avatar
10 votes
1 answer
509 views

Should one perform geometry optimisation before calculating electronic/phonon band structures via DFT?

I am new to DFT calculations and I would like to get the electronic and phonon band structures of FeSn (1 kagome layer and 1 Sn layer in between). My question is, is it absolutely necessary to first ...
electronblue's user avatar
3 votes
1 answer
181 views

Simple and quick way to get phonon dispersion?

I want a simple phonon dispersion calculation, the lighter the program the better I do not want to install some huge package like QuantumExpresso just for that. Another way would be to find a database ...
Jellium mind's user avatar
2 votes
0 answers
40 views

Can we create a phonon with a specific wavenumber that persists in the system for a long time? [closed]

The phonon number is not a conserved quantity, they add up as dictated by the dispersion relation until the Planck distribution is reached. However, I would need the k=PI/a phonons not to disappear ...
user3916292's user avatar
9 votes
1 answer
383 views

Stability using Phonon Calculation

While performing phonon calculation using finite difference method, we get normal modes printed in the outcar file. Now there is a distinction between two different types of modes in the outcar file. ...
mehak g's user avatar
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2 votes
0 answers
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How to determine the TA/LA by phonopy [closed]

I would like to ask how to use PHONOPY to define which band is LO, TO or ...
Hu Chenhui's user avatar
2 votes
0 answers
207 views

Phonon dispersion calculation error [closed]

I am getting the following error error in routine phq_readin (1): reading xq I don't understand what is this error about.
epsilon02fft's user avatar
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3 votes
0 answers
95 views

Interpreting Phonon calculations for 2D materials [closed]

What is the meaning of phonon calculation in 2D materials? And is it enough to predict the stability of materials based on positive phonon only?
Maulesh VALA's user avatar
1 vote
0 answers
215 views

can anyone please explain what is meaning of band.conf , mesh.conf and pdos.conf in phonon calculation? [closed]

Can anyone please explain, what is the physical meaning of band.conf, mesh.conf and pdos.conf in phonon calculation? if it is possible please explain about tags used in it.
Maulesh VALA's user avatar
10 votes
1 answer
2k views

How to determine LA/TA, ZA/ZO and LO/TO by PHONOPY

I would like to ask how to use PHONOPY to define which band is LO, TO or LA, TA, or ZO or ZA. I attach a picture from https://iopscience.iop.org/article/10.1088/0953-8984/28/10/103005
Binh Thien's user avatar
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9 votes
1 answer
137 views

Are there other kinds of stability of materials? How to demonstrate that with computation approaches?

I have known some kinds of stability of materials, such as: Mechanical stability; Dynamical stability; Thermal stability In particular, they can be studied with first-principles computational ...
Jack's user avatar
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12 votes
1 answer
619 views

Phonon dispersion and phonon DOS

A follow up question for this question. What are the different properties that can be deduced from a phonon dispersion curve and Phonon DOS? Also if possible explain how to deduce them?
Thomas's user avatar
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12 votes
1 answer
223 views

Phonon Calculations for Bilayer 2D systems

I am facing problems in calculating the phonon band structure for bilayer 2D systems. While the band structure mostly shows positive frequencies for the 1 layer system, going to 2 layers makes some ...
Shahid Sattar's user avatar
13 votes
2 answers
333 views

Can we do anything to reduce the number of displacements in a frozen phonon lattice dynamics study?

I realize that the more ordered the supercell is, the lower the number of displacements. Perhaps, we could say the same with respect to symmetry. Is there anything that can be done to reduce the ...
Hitanshu Sachania's user avatar
19 votes
1 answer
627 views

What do phonon dispersion (or lattice dynamics) studies include?

I use the codes phonopy and phonopy-qha for phonon dispersion studies. phonopy-qha gives ...
Hitanshu Sachania's user avatar