Questions tagged [phonopy]

Tag this when using the phonopy package for phonon calculations at harmonic and quasi-harmonic levels.

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Getting some errors while extracting the data for phonon band strucutre

I am getting some errors while extracting the data for phonon band structure: ...
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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?
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can anyone please explain what is meaning of band.conf , mesh.conf and pdos.conf in phonon calculation?

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.
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Tools to Visualize Phonons

Software such as ChemCraft or GaussView is easy to find for vibrational calculations in gas phase, but I am finding it much more difficult to find good visualization software for phonons. I have ...
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How to solve this Phonopy-related problem?

I have used the finite displacements method for phonon spectrum calculation, and when I typed the command to create force sets: ...
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Which IBRION tag should be used for finite displacement method in calculating Phonons spectrum?

I am planning to use the finite displacement method for calculating phonon spectrum, and I have prepared the INCAR file below to try it on a transition metal trihalide monolayer (e.g., VI$_3$). I ...
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6 votes
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Lattice Thermal conductivity calculation error

I have been trying to calculate Lattice Thermal Conductivity on my system using QuantumEspresso. I used phonopy and phono3py. I was successful to run these codes on Si system for practice. Now when I ...
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6 votes
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What is the minimum supercell size for phonon spectrum calculation for this monolayer system?

Following the previous threads on this topic, I would like to know the minimum supercell size suitable for Phonon spectrum calculation using Phonopy (DFPT) for CrI$_3$ monolayer system given by this ...
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How can I find primitive axis for any bulk or 2D (monolayer) material [closed]

I am doing DFPT calculations using VASP+Phonopy. To plot phonon band structure, I need a band.conf file in which we need to ...
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How to correct units in the band.yaml file of QE, to band.yaml of VASP [closed]

I see from the phonopy web page 1 that the physical unit systems used for the calculators are different for different codes 1. On the same page, it is mentioned that "For these sets of physical ...
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Calculating lattice thermal conductivity using Quantum ESPRESSO and phonopy

How should I calculate lattice thermal conductivity in Quantum ESPRESSO? I have installed phonopy. My Linux distribution is Ubuntu.
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8 votes
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Calculation of linear coefficient of thermal expansion using VASP-Phonopy for Hexagonal material

We use quasi-harmonic approximation using VASP-Phonopy. In whole calculation we only assume Free energy as function of volume but in case of HCP material which have ...
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Phonon frequencies and free energy with respect to polymorphs

I have a material that can crystallize in either a cubic or tetragonal polymorph depending on the synthesis. I used DFPT in VASP and calculated the phonon band structures. I see that the cubic has all ...
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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? (...
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2 answers
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Temperature effect on elastic constant using VASP

I want to incorporate the temperature effect on elastic constant (EC) of a system using VASP. From literature, there are two ways which can be used to get the temperature effect on EC i) ab initio ...
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10 votes
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Reliability about the predicted two-dimensional crystal structures based on DFT high-throughput calculation?

Computational 2D Materials Database (C2DB), 2D structures and layered materials, and 2D Materials Encyclopedia are three major databases for two-dimensional materials based on DFT calculation. However,...
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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
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Why do we need to build a supercell to use the DFPT in Phonopy interfaced with VASP?

The following passage about the merits of density-functional perturbation theory (DFPT) is extracted from this seminal paper: Phonons and related crystal properties from density-functional ...
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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 ...
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13 votes
1 answer
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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 $\omega_i$ ...
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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 ...
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4 votes
1 answer
432 views

Best practice(s) for q-points convergence in phonon density of states calculations

The answer can be a complete description of all the things we must be attentive to while converging q-points. A peculiar thing that I feel contradicted about: Generally, we don't take an equal # of k-...
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8 votes
1 answer
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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 ...
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9 votes
2 answers
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"Input forces are not enough to calculate force constants" Phonopy error?

I am doing a phonon calculation for a phase using a 2x2x1 supercell (after geometry optimization of the structure). I am getting an error when computing the DOS and band structure after computing the ...
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26 votes
3 answers
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How big should a supercell be in phonon calculations?

Is 2x2x2 enough, or is larger needed? I know that a convergence test must be carried out, but increasing supercell size enormously increases computational time, and I am using the Python program ...
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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 ...
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19 votes
1 answer
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What do phonon dispersion (or lattice dynamics) studies include?

I use the codes phonopy and phonopy-qha for phonon dispersion studies. phonopy-qha gives ...
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18 votes
1 answer
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Are there differences in accuracy and reliability between the frozen phonon method and Density Functional Perturbation Theory?

When proposing or predicting new materials, whether in the bulk or in two dimensions, it is important to discuss the stability of the system. This is usually done through thermodynamics and(or) ...
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