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Questions tagged [phonon-density-of-state]

For questions about the calculation of phonon density of states (DoS) or the theories involved in them.

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20 votes
1 answer
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What do negative phonon frequencies signify?

Negative frequencies "in general" mean the direction of displacement is reverse to that in positive frequencies. Does it mean two frequencies with opposite signs but the same magnitude give ...
Hitanshu Sachania's user avatar
13 votes
1 answer
190 views

Phonon density of states in statistical thermodynamics

Phonon density of states (DoS), $g_{(\omega_i)}$, help understand the distribution of states across frequencies of vibration. $\int g_{(\omega_i)}d\omega_i =$ the number of states between $\omega_i$ ...
Hitanshu Sachania's user avatar
12 votes
1 answer
725 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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10 votes
0 answers
255 views

Phonon density of states as a function of frequency vs energy [closed]

Lattice dynamics codes like Phonopy output density of states, $g_{(\omega)}$, as a function of frequency. Since $\int g_{(\omega)}d\omega$ is the number of states ...
Hitanshu Sachania's user avatar
8 votes
1 answer
589 views

Should all q-points in the first Brillouin zone be sampled in phonon density of states calculations?

For electronic density of states (DoS) calculations with VASP, it is recommended that VASP's internal symmetry routine is turned ...
Hitanshu Sachania's user avatar
7 votes
1 answer
317 views

Obtaining phonon density of states from Density Functional Theory

From Statistical Mechanics obtain an expression for the heat capacity of a solid is given by1: \begin{equation} \tag{1} {C_V}\left( T \right) = k\int\limits_0^\infty {\frac{{{{\left( {uv} \right)}^2}{...
Camps's user avatar
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7 votes
1 answer
148 views

Can we translate vibrational frequencies at q-points to vibrational frequencies of atoms?

Lattice dynamics codes like phonopy output vibrational frequencies at q-points. Can we get data of vibrational frequencies for each of the atoms in the supercell? (...
Hitanshu Sachania's user avatar
6 votes
0 answers
160 views

Odd/even q-point mesh in harmonic phonon density of states (DoS) calculations [closed]

Total DoS for two different q-point grids, $100\times100\times100$ and $101\times101\times101$, are graphed above. The DoS for $63\times63\times63$, $65\times65\times65$, $71\times71\times71$, $72\...
Hitanshu Sachania's user avatar
5 votes
1 answer
240 views

VASPKIT and SeeK-path recommend different paths. Which one to choose?

I want to get the phonon density of states for a monolayer MoS2. For this, I need phonon dispersion curves, and to choose a path where to compute phonons. VASPKIT recommends Γ-M-K-Γ SeeK-path ...
Vladislav Gladkikh's user avatar
5 votes
1 answer
250 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
0 answers
54 views

2D Infrared spectroscopy for bulk systems using molecular dynamics

There are some questions and answers (1,2) on this site regarding simple infrared and vibrational density of states calculations with molecular dynamics and there any simple algorithmic descriptions ...
mykd's user avatar
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5 votes
0 answers
55 views

How to derive specific heat of a crystalline material from phonon density of states? [closed]

I have done a simulation of a crystalline material using DFT and have extracted its normal modes and its phonon density of states. Does anyone have an algorithm/code or a detailed resource that can ...
Elie H's user avatar
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4 votes
1 answer
75 views

Causes of Straight Bands in Phonon Dispersion Calculations

In my phonon calculation utilizing DFPT in VASP for a monolayer material with space group 187, I've noticed that while most of the phonon bands are positive, two of them appear to be straight. What ...
Farah Shehzadi's user avatar
4 votes
1 answer
52 views

Exploring Phonon Dispersion in Two-Dimensional Materials: Analytical Techniques and Mode Identification

How can one analyze the phonon dispersion of 2D materials like graphene to discern specific curves corresponding to particular phonon modes, such as acoustic or optical, as well as longitudinal and ...
Farah Shehzadi's user avatar
3 votes
0 answers
103 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
2 votes
0 answers
42 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
1 vote
0 answers
273 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
0 votes
0 answers
4 views

Can temperature dependent phonon dispersion be solved by EPW package of Quantum Espresso?

Yesterday, I posted a question (How to plot temperature dependent Phonon dispersion using Quantum Espresso?) related to temperature dependency of phonon dispersion. Would it be possible to solve this ...
Muhammad Hasan's user avatar