Phonopy group velocity. Using these intermediate data, phonon properties are .

Phonopy group velocity 0001, seed = 0) [source] ¶. Symmetry) – phonopy’s Symmetry (str, 'Neto' or 'random') – ‘Neto’: construct irreps from a fixed chain of subgroups of little co-group ‘random’: construct irreps by numerically diagonalizing a random GROUP_VELOCITY = . txt note: # The unit of frequency is the same as that set in phonopy Hi, It may be easier to write mesh quantities to hdf5, e. 3 Structural phase transition under shear strain 10 5. The boxes are jobs being done by phonopy, and Firstly, what is the difference between group velocity and gv_by_gv in hdf5 file? I notice they are not the same. xyz supercell-002-forces-1_0. This class adds band structure plots to Matplotlib axes. In addition, this file is read when the restart mode is turned on (RESTART = 1). 在phonopy manual中有详细介绍该软件相关Group Velocity的计算方法，和计算有关的计算方式. I got the "NaCl-gv. 4 With non-analytical term correction, the PDOS may not change very much because it mainly affects to the density of \[\begin{split} g f_{\mu}(\kappa; \mathbf{q}\omega_{\mathbf{q}}\nu) &= \sum_{\mu'\nu'} f_{\mu'}(\kappa'; \mathbf{q}\omega_{\mathbf{q}}\nu') \Gamma^{ (\mathbf{q Contribute to phonopy/phonopy development by creating an account on GitHub. In the manual, it is said the units of group velocity are The physical unit is [image: \text{THz}\cdot\text{\AA}] (without [image: 2\pi]). Then I think the following are not required *nac_params = parse_BORN(primitive, filename="BORN")phonon. hdf5 --gv --average |tee kaccum. However, in lossy media, energy velocity diverges from group velocity. Irreducible representations of normal modes. Group velocity# GROUP_VELOCITY # The phonopy’s default force constants calculator is based on finite difference method, for which atomic displacements are made systematically. I checked it as below. Thermal ellipsoids / Mean How to calculate the group velocity using Phonopy? Question. `. pyplot as plt import seaborn as sns import phonopy import seekpath import numpy In lossless periodic media, the concept of group velocity is fundamental to the study of propagation dynamics. html Togo On Sat, Sep 9, 2023 at 3:01 PM elkana Firstly, how can i get group velocity and phonon lifetime by phono3py? I tried to use "phono3py-kaccum --pa="0 1/2 1/2 1/2 0 1/2 1/2 1/2 0" -c POSCAR-unitcell kappa-m111111. Lattice thermal conductivity tensor (Peierls term). yaml is viewed using the tool phonopy-bandplot (phonopy-bandplot). io/phono3py/auxiliary-tools. By chance, I have implemented In this review, basic formulae of phonon properties are reviewed with the phonon calculation examples performed using the phonon calculation codes, phonopy and phono3py, combined I took that supercell, SPOSCAR and used VASP to generate the Hessian matrix with the attached INCAR. I missed it someway One more query, to convert THz. conf" file. The value is given in micrometre. I have two inquiries: > >> > >> > >> 1- Calculating the group velocity in phonopy and the one obtained by > >> phono3py seem to be different not only shape wise but magnitude wise! > For > >> example, in the former , the maximum value of the velocity is around > 41000 > >> m/s whereas in phono3py , I am getting values of ~ 21000 m/s. 01 then use "python gv. py) ? Query 2: I have plotted the said graph, deleting the primitive_matrix. U. 3. Phonon thermal properties: Free energy, heat capacity (Cv), and entropy. I have two inquiries: >> >> >> 1- Calculating the group velocity in phonopy and the one obtained by >> phono3py seem to be different not only shape wise but magnitude wise! For >> example, in the former , the maximum value of the velocity is around 41000 >> m/s whereas in phono3py , I am getting values of ~ 21000 m/s. Phonon group velocity is an important factor that affects the lattice thermal conductivity. structure. 1. Non-analytical term correction is implemented in C, which accelerates the calculation speed. Group velocity can be calculated using GROUP_VELOCITY tag or --gv option (GROUP_VELOCITY). Thermal ellipsoids / Mean square displacements. After this subspace diagonalization, the new diagonal matrix Dear Phono3py users, I am using VASP and phono3py to determine the thermal conductivity of GaN. Github: https://github. If more supercells with displacements were created in the step 1, all . The default value, 1 metre, is just used to avoid divergence of phonon lifetime and the contribution to the thermal conductivity is considered negligible. The following features of phonopy are highlighted: * Phonon band structure, phonon DOS and partial-DOS * Phonon thermal properties: Free energy, heat capacity (Cv), and entropy * Phonon group velocity * Thermal ellipsoids / Mean square displacements * Welcome to phono3py#. Phonon code. Feb-7-2013: Version 1. Please note: the files containing the forces can be prefixed with the PROJECT_NAME as specified in the original CP2K input file. yaml for VASP and QE codes are the same? Also, the default displacement distance for VASP Dear Prof. out files are the saved text files of standard outputs of the QE-PW calculations. 3 Phonon spectral function 12 6. interface. - `Phonopy. ndarray [Any, numpy. optical)? The help will be highly appreciated. --fz option is used to subtract residual forces frown the forces calculated for the supercells with displacements. Togo for your nice clarification. > However, I calculated the group velocity manually from d_omega/d_q where > omega is frequency*2pi, and q is calculated from reciprocal phonopy manual, Release 1. See examples, commands and tips for generating and analysing the data. The optimized lattice structure could be expanded by phonopy [51, 52] and the thirdorder. phono3py_disp. out files are given in the above command. shape Out[6]: (35, 6) The first and second dimensions of the arrays give the q-points and band indices, respectively. Forces on atoms or force constants are calculated by your favorite calculator (shown by the octagons in the work flow). au (bohr). Collective atomic modulation analysis with irreducible space-group representation. yaml The following features of phonopy are highlighted: Phonon band structure, phonon DOS and partial-DOS. TRUE. There are two ways to calculate, (1) atomic forces from finite displacements and (2) given force constants. Supercell # Return Phonopy’s Hi, I see the problem occurs by the finite difference technique that I implemented. of phonon dispersion? Please provide details, example or link. The following features of phonopy are highlighted: Phonon band structure, phonon DOS and partial-DOS. py, and Fourthorder. In this unit, I talk about the phonon calculations in The difference between group velocity and phase velocity also changes the carrier–envelope offset of the pulse. conf" it gave me the graph of band structure. ## Nov-16-2019: Version 2. PREFIX. I have not noticed any example of this in the manual or in the tutorial section. 0The Group velocity near Gamma point related with sonic wave from experimental data. The group velocities are written into a yaml file corresponding to the run mode in Cartesian coordinates. it gave me the graph of band structure. phonopy import get_pmg_structure, get_phonopy class spgrep_modulation. The Phonopy package 56 was used to obtain the second Each phonon at a given wavevector q will simply move along the x-axis with a velocity equal to the x-component of the group velocity \({v Unfortunately, I couldn't understand your explaination. In phonopy, force constants are generated using the supercell method with finite displacements. If i am correct, the second column is the accumulative group velocity, and the third column is the derivative of the second column. conf" command to generate band. Mesh sampling mode# Key. true. save reported by PR#104 ## Nov-13-2019: Version 2. sxxx and gxxx appear optionally. 11 Irreducible representation 9 4. I am trying to do that through a python script > (please see the attached file FeSi_group_velocity. Asked 4th Mar, 2017; M. phonon. conf # creates the band plot (will fail if it cannot display back to your desktop) phonopy-p-s band. yaml has to be located in the current directory because the information on atomic displacements stored in phonopy_disp. As shown above, group velocity calculation is implemented to output in [distance x ordinary-frequency] = [angular-frequency Dear all (1) How to get group velocity and relaxation time? (2) How to calculate group velocity of TA, TA', LA, . Several approaches can be employed to calculate supercell force constants. kappa-m323220. class BandPlot: """Band structure plotting class. The format of the output is as follows: The first column gives frequency in THz, and the second to seventh columns give the Hi, For your last question, I think no. The following is the list of the force constants HI, THz. Quasi-harmonic Phonon Calculation 9 4. yaml which contains the w(k) values phonopy-p band. Dear Experts I have found in the manual that the unit of the group velocity is THz. Let us focus on the case of phonons in crystals. 11. hdf5 is the output file of thermal conductivity calculation, which is passed to phono3py-kaccum as the first argument. Once that was done, I used PhonoPy to generate the force constants with "phonopy - I think phono3py and phonopy give the same group velocity. Anharmonic Phonon Calculation 11 5. > > In the manual, it is said the units of group velocity are The physical > unit is [image: \text{THz}\cdot\text{\AA}] (without [image: 2\pi]). yaml or phono3py. py" file in the example directory. 2 Thermal expansion 9 4. yaml for VASP and QE codes are the same? Also, the default displacement distance for VASP How to calculate the group velocity using Phonopy? Question. yaml Function: Extract phonon frequencies and related data in band. Thread: [Phonopy-users] Uunit for frequency and group velocity in yaml files for VASP and QE code and displ Brought to you by: atztogo. Primitive, primitive_symmetry: phonopy 'Neto' or 'random') – ‘Neto’: construct irreps from a fixed chain of subgroups of little co-group ‘random’: construct irreps by numerically diagonalizing a 3. The first derivative of this expression, which is for example used for group velocity calculation, is described in the following paper: Atsushi Togo, Laurent Chaput, and Dear Prof. Symmetry condition for group velocity Supercell construction Band connectivity Theme by (phonopy. (TDISP) A new tag WRITEDM and an option --writedm are See phonopy PRIMITIVE_AXES tag (--pa option) at primitive-axis is the group velocity and \(L\) is the boundary mean free path. phonopy-bandplot can convert the data in the YAML format to that in the gnuplot-style format using the --gnuplot option. , 2008) code. yaml has some negative values for Group Velocity. conf # creates the band plot and saves it as a pdf file (requires display) The first argument is that of the perfect supercell to subtract residual forces --fmax FMAX Maximum frequency used for DOS or moment calculation --fmin FMIN Minimum frequency used for DOS or moment calculation --fpitch FPITCH Frequency pitch used for DOS or moment calculation --gc, --gamma-center Set mesh as Gamma center --gv, --group-velocity Calculate Details of kappa-*. conf # generates band. > > The concern is, if someone want to calcualte the group velocity at an > arbitrary point in the BZ, how can he make sure it is calculated correctly - > no via the Fourier Transform of the velocity-velocity autocorrelation function f(ω) = 1 √ 2π Z ∞ −∞ e−iωt X I hv I(t)·v I(0)i hv I(0)·v I(0)i dt, (1) Function f(ω) has peaks at the vibrational frequencies. > > One more question please, How can I use larger q_length ( default is 1e-4) > to calculate group velocity. \[\begin{split} g f_{\mu}(\kappa; \mathbf{q}\omega_{\mathbf{q}}\nu) &= \sum_{\mu'\nu'} f_{\mu'}(\kappa'; \mathbf{q}\omega_{\mathbf{q}}\nu') \Gamma^{ (\mathbf{q In particular, Phoebe interfaces with phonopy/phono3py and Quantum ESPRESSO However if is a degenerate eigenvalue, we cannot readily identify the velocity matrix element with the group velocity: in this case, we select the degenerate subspace of the matrix and diagonalize it. (TDISP) A new tag WRITEDM and an option --writedm are 3. cells. 10 Phonon group velocity Inside the phonopy workflow, the VASP workflows 100) are called to run the first-principles calculations to obtain forces of atoms in supercells for supercell force constants calculation and Born effective charges and dielectric constant tensor required for NAC. When spatially averaged, the group velocity is numerically equivalent to energy velocity, defined as the ratio of energy flux to energy density of modal fields. hdf5 file #. ----- thermal displacementphonopy --help Mean Thanks Prof. from The velocity of a phonon is determined as the group velocity of the corresponding classical waves and has the form: (2. Files name, e. , phonopy-load --mesh 30 --gv --hdf5 Then you will get mesh. To obtain the group velocity of the acoustic branch and optical branch at different frequencies, the squared group velocity is plotted in Fig. DIM = 2 2 2. For example, the following physical values are obtained: phonopy band. This problem only occurs in some cases when the phonon mode is degenerate at zone boundary. yaml file, but it's rather messy because it requires to interpolate if the q point does not belong to the mesh. Since the integral is taken from 0 Dear Prof. units import VaspToTHz. group_velocity_delta_q: Optional[float] = None, symprec: float = 1e-5, is_symmetry: bool = True, store_dense_svecs: bool = True, Group velocity can be calculated using GROUP_VELOCITY tag or --gv option (GROUP_VELOCITY). Can sound velocity be extracted from group velocities of phonons? في الثلاثاء، 4 جانفي 2022 06:40 Atsushi Togo <atz@gm> كتب: > Hi The harmonic interatomic force constants (IFCs) and phonon dispersion are obtained from the PHONOPY package by the finite displacement method with a 7 × 7 × Due to the comparable phonon group velocity and degree of anharmonicity between the stable graphene-like borophene and graphene, there must be another mechanism responsible for the Dear Prof. We used Phonopy [25], a package implemented with the finite displacement method (FDM), to calculate the phonon dispersion and extract second-order interaction force constants (2nd-order Extremely helpful and detailed answer Togo! A follow-up question regarding the issue of small imaginary modes near gamma for acoustic modes. Modulation (primitive_symmetry, supercell, dynamical_matrix, qpoint, nac_q_direction = None, factor = 15. *Best Regards * *ขอแสดงความนับถือ* *Meena Riitiruam* *มีนา ฤทธิร่วม* The comparison of (a) group velocity, (b) the group velocity of twelfth optical branch ZO 3, (c) the scattering channel-resolved phonon phase space and (d) the summarized absorption and emission Group velocity calculation with the finite difference method is still able to be activated using GV_DELTA_Q tag or --gv_delta_q option. I am attaching a MS word document showing > the group velocity using non-shifted, shifted meshes, and calculated from > the dispersion relations directly along high symmetry directions. Could someone please give a script for QE+Phonopy so that I can plot Group Velocity for different phonon modes (LA/TA/ZA. Phonon group velocity. In analogy with the refractive index, the group index (see the equation above) can be defined as the ratio of the group The following features of phonopy are highlighted: - {ref}`Phonon band structure `, {ref}`phonon DOS and partial-DOS ` - {ref}`Phonon thermal properties `: Free energy, heat capacity (Cv), and entropy - {ref}`Phonon group velocity ` - {ref}`Thermal ellipsoids ` / {ref}`Mean square displacements ` - {ref}`Irreducible representations of normal modes ` - {ref}`Dynamic structure Please note: the files containing the forces can be prefixed with the PROJECT_NAME as specified in the original CP2K input file. 10 Phonon group velocity 8 3. Description. So in my case, what will be the unit THz. 1 Mode Grüneisen parameter 9 4. The Phonopy package can be used to compute harmonic force constants (FC2), dynamical spgrep-modulation#. . S5, Phonon group velocity of 2H-MoA2Z4 monolayers predicted using the PHONOPY with MTP. py). The following features of phonopy are highlighted: - {ref}`Phonon band structure `, {ref}`phonon DOS and partial-DOS ` - {ref}`Phonon thermal properties `: Free energy, heat capacity (Cv), and entropy - {ref}`Phonon group velocity ` - {ref}`Thermal ellipsoids ` / {ref}`Mean square displacements ` - {ref}`Irreducible representations of normal modes ` - {ref}`Dynamic structure The workflow of API Phonons is illustrated in Fig. Please send your questions to the I have two inquiries: 1- Calculating the group velocity in phonopy and the one obtained by phono3py seem to be different not only shape wise but magnitude wise! For example, in the former , the maximum value of the velocity is around 41000 m/s whereas in phono3py , I am getting values of ~ 21000 m/s. py. I have two inquiries: 1- Calculating the group velocity in phonopy and the one obtained by phono3py seem to be different not only shape wise but magnitude wise! For example, in the former , the maximum value of the velocity is around 41000 m/s whereas in phono3py , I am getting values of ~ 21000 m/s. The group velocity of the mode n=5 tends monotonically to the bulk velocity v TA 2 (AlN). The following is the list of the force constants calculator currently possible to be invoked from phonopy. I think the data structure may be obvious, which is like In [5]: f['group_velocity']. 0 - CP2K interface is provided by Tiziano Müller. > > > > I compute with Si-PBEsol example by > > % phono3py --dim="2 2 2" --pa="0 1/2 1/2 1/2 0 1/2 1/2 1/2 0" -c > > POSCAR Phono-Group-velocity-from-band. 1%, due to the higher phonon group velocity [41], as shown in Fig. vasp import write_vasp from pymatgen. modulation. Direction of q-vector perturbation used for NAC at q->0, and group velocity for degenerate phonon mode in q-points mode -q, --quiet Print out smallest information --random-seed RANDOM_SEED Random seed by a 32 bit unsigned integer --rd RANDOM_DISPLACEMENTS, --random-displacements RANDOM_DISPLACEMENTS Number of supercells with random In this file, phonon frequency, group velocity, and anharmonic phonon linewidths are printed. I haven't performed the non-analytical correction and I don't have a BORN file. Here the residual forces mean that the forces calculated for the perfect supercell for which the (formulations)= # Formulations ## Second-order force constants Potential energy of phonon system is represented as functions of atomic positions: ```{math} V[\mathbf{r}(j_1 l_1),\ldots,\mathbf{r}(j_n l_N)], ``` where {math}`\mathbf{r}(jl)` is the point of the {math}`j`-th atom in the {math}`l`-th unit cell and {math}`n` and {math}`N` are the number of atoms in a unit cell and I am confused about the > 2pi factor for phonon group velocity. 633302300230191, degeneracy_tolerance = 0. This software calculates phonon-phonon interaction and related properties using the supercell approach. Using the command option of -o, the file name can ## Dec-22-2019: Version 2. property supercell: phonopy. it is very messy as it contains info of band 1 to 24 whereas including the primitive_matrix only band 1 to 6 are present. In particular it has branches, three of which are acoustic ones. Secondly, how can i get group velocity from phono3py? I tried to use "phono3py-kaccum --pa="0 1/2 1/2 1/2 0 1/2 1/2 1/2 0" -c POSCAR-unitcell kappa-m111111. band. Dynamic structure factor for INS and IXS. Dear users, Does anybody know how to calculate the group velocity at an arbitrary q-point with Phonopy? I've been doing it by using the output contained in the mesh. from __future__ import annotations from pathlib import Path import warnings from itertools import product from dataclasses import dataclass import matplotlib. dat". Q_DIRECTION = 1 0 0 ``` ## Group velocity (group_velocity_tag)= ### `GROUP_VELOCITY` Group velocities at q-points are calculated by using this tag. mxxx, show the numbers of sampling mesh. 13. Generate modulated cells based on dynamical matrix of phonon. io. The phonopy's default force constants calculator is based on finite difference method ShengBTE accepts two different formats for second-order IFCs: that generated by Phonopy [34] (typically using a supercell and a variety of DFT back-ends) or the one created by Quantum Espresso [33] but in contrast with v λ τ λ 0 it does not have to be parallel to the group velocity of the mode. 2 - Collection of minor updates: adding docstrings, refactoring group velocity code, and updating examples. Using the command option of -o, the file name can Thank you. dtype [numpy. float64]] # Return translations of little group at qpoint. Kindly Click Here: https://bit. 2 Phonon lifetime 12 5. Asked 4 March 2017; M. respectively, where \(\alpha\), \(\beta\), , are the Cartesian indices, \(j\), \(j'\), , are the indices of atoms in a unit cell, and \(l\), \(l'\), , are 3. group_velocity. au to km/s, do we need to multiply it with 2. Dear Phono3py users, I am using VASP and phono3py to determine the thermal conductivity of GaN. core import Structure from pymatgen. Togo, How can I calculate phonon group velocity and plot it using phonopy. Muzaffar; Dear all, I used the tags in "mesh. Group velocity at each phonon mode in the Cartesian coordinates defined in the unit cell. --fz #. Using these intermediate data, phonon properties are The LDA phonon dispersions and polarization vectors were computed with Phonopy 21, from which we computed Table 2 Group velocity of acoustic phonons along the high-symmetry directions from ```bash % phonopy -f disp-001/FORCES disp-002/FORCES ``` (cp2k_force_sets_option)= #### CP2K interface `FORCE_SETS` file is created from `phonopy_disp. pi? The properties such as phonon dispersion relation, phonon group velocity and Grüneisen parameter are calculated by using the PHONOPY code combined with Vienna ab-initio simulation Package (VASP The phonon band structure is calculated using the finite displacement method as implemented in the phonopy (Togo et al. 101) All the properties of the classical wave spectrum are valid for the energy spectrum of phonons. py script [53] For ε = 0. kl. Attributes-----xscale : float. phonopy-load - manual page for phonopy-load 2. How to calculate the group velocity using Phonopy? Question. symmetry. I also observed this in a material I am studying in Phonopy, yet Phonopy (qpoints. So I'm sorry that I can't answer. yaml and gruneisen. and above all the band. To run this command, phonopy_disp. xyz ``` Please note: the files containing the forces can be prefixed with the `PROJECT_NAME` as specified The phonopy and phono3py codes employ a linear tetrahedron method where several techniques are picked and mixed from the various reports, notably, by MacDonald et al and Blöchl et al . property primitive: phonopy. Angstrom. For me, your sound velocity was not clear. yaml file) is still able to calculate various properties such as group velocity, mode Gruneisen parameter, and heat capacity. yaml are used to Download scientific diagram | , (a) Phonons' group velocities calculated with PHONOPY code (b) and phonons' life time acquired with ShengBTE package for BeO to MgO and CaO monolayers. 4. 3 c, P-B scattering was relatively severe, resulting in a higher total scattering rate. I will try and let you know. Contribute to phonopy/phonopy development by creating an account on GitHub. g. Suppose I created primitive cell PPOSCAR by command "phonopy --symmetry" , then how to know the primitive axis which is used in band plot as well as group velocity plot (NaCl-gv. 1 - Fix a bug on Phonopy. 6. Primitive # Return Phonopy’s primitive cell. Phonon group velocity; Thermal ellipsoids / Mean square displacements; Irreducible representations of normal modes; Quasi-harmonic approximation: Thermal expansion, The following features of phonopy are highlighted: Phonon band structure, phonon DOS and partial-DOS. hdf5. I am confused about the 2pi factor for phonon group velocity. yaml produced by Phonopy Usage: Use "phonopy band. Summary Files Reviews Does it mean that the final unit for frequency and group velocity in band. yaml is necessary to be located under the current directory to read the crystal structure. The implementation in the phonopy and phono3py codes is structured as schematically illustrated in figure 10. Togo On Sunday, August 23, 2015 The lattice thermal conductivity of these four materials are anisotropic, with the value of a a x i s larger than that of b a x i s, besides, GeX exhibits larger value of κ L compared with SnX, which can be attributed to the higher phonon group velocity of GeX, and reflects that the phonon group velocity has a greater influence on the lattice thermal conductivity than the Dear Phonopy users, I would like to request for a command used to extract or plot group velocity from phonopy or phono3py using VASP output. phonopy-load doesn’t have this option. q点处的 群速度 用这个标签计算。群速度被写入一个yaml文件，该文件对应于 笛卡尔坐标 下的运行模式。物理单位取决于输入文 Above 15 THz, the variation trend of group velocity at different temperatures is not obvious, so the accurate value of group velocity only can be obtained by ShengBTE software. Using these intermediate data, phonon properties are For example, the group velocity for the mode with n=1 at moderate k is v TA 2 (AlN), while at large k the group velocity is v TA 2 (GaN), although the total width of the cladding AlN layers is five times larger than the width of the core GaN layer. When we doubt it is good to check acoustic mode next to the Gamma point. phonopy version 1. from phonopy. (TDISP) A new tag WRITEDM and an option --writedm are Group velocity# GROUP_VELOCITY # The phonopy’s default force constants calculator is based on finite difference method, for which atomic displacements are made systematically. 4 With non-analytical term correction, the PDOS may not change very much because it mainly affects to the density of where κ λ are the modal thermal conductivities, C λ are the (volumetric) heat capacities, v λ ⊗ v λ are the tensor products of the group velocities, τ λ are the lifetimes, V is the volume of the unit cell and N is the number of phonon Dear Prof. and then used the command "phonopy -p --gv mesh. I am using quantum espresso. io/phono3py/hdf5_howto. yaml it is also clearly mentioned that the units are in a. 2 (b). We have provided a series of Python modules for interfacing atomistic simulation programs such as LAMMPS and Quippy with force constants (FCs) calculators, including Phonopy [44], Thirdorder. Work flow of phonopy is shown schematically. Direction of q-vector perturbation used for NAC at q->0, and group velocity for degenerate phonon mode in q-points mode -q, --quiet Print out smallest information --random-seed RANDOM_SEED Random seed by a 32 bit unsigned integer --rd RANDOM_DISPLACEMENTS, --random-displacements RANDOM_DISPLACEMENTS Number of supercells with random where l is the phonon MFP, v is the phonon group velocity, C MFP is the volumetric heat capacity per unit phonon MFP and s indexes the polarization of phonons. yaml` and CP2K output files, with: ```bash % phonopy -f supercell-001-forces-1_0. conf file and what is the command to determine the group velocity? Got a Learn how to use phonopy to calculate and plot these quantities that describe the vibrational dynamics and thermal conductivity of materials. group_velocity = . conf file and what is the command to determine the group velocity? Thanks Hi, Please read https://phonopy. Download scientific diagram | Fig. py" command to get gv. Details of kappa-*. I see in the example directory that there are some python scripts but that are for VASP+Phonopy. The first derivative of this expression, which is for example used for group velocity calculation, is described in the following paper: Atsushi Togo, Laurent Chaput, and Dear Experts I have found in the manual that the unit of the group velocity is THz. html https://phonopy. Yes, actually in phonopy. Dear Prof. get_group_velocity()` is deprecated Phonopy is an open source package for phonon calculations at harmonic and quasi-harmonic levels. As shown above, group velocity > calculation is implemented to output in [distance x > ordinary-frequency] = [angular-frequency / (reciprocal distance with > 2pi)], where the definition is briefly explained at wikipedia, > Bose–Einstein distribution function, frequency, and group velocity of the corresponding phonon mode. 3# Arbitral projection direction is allowed for thermal displacements calculation. I output the frequencies, group velocities, etc. 1 Phonon coordinate transformation 11 5. 1 --group-velocity Calculate group velocities at q-points --gv-delta-q GV_DELTA_Q Delta-q distance used for group velocity calculation --hdf5 Use hdf5 for force constants --hdf5-compression HDF5_COMPRESSION hdf5 compression filter (default: gzip) --hiphive Use hiPhive In phonopy, force constants are generated using the supercell method with finite displacements. Return rotations of little group at qpoint. u. Thermal ellipsoids / Mean In phonopy, the group velocity is calculated from dynamical matrices at finitely displaced q-points, which is very similar to that of mode Gruneisen parameters. shape Out[5]: (35, 6, 3) In [6]: f['frequency']. set_nac_params(nac_params)* I think the structural information Dear Prof. Yes, this is not well written in the documentation. com/phonopy/spgrep-modulation Document Symmetry condition for group velocity Supercell construction Band connectivity Theme by the Executable from pathlib import Path import numpy as np import phonopy from phonopy import Phonopy from phonopy. The phonon group velocity, total (v) and mode resolved (vi), Gru¨neisen parameter total (γ) and mode resolved (γi), have been extracted from the harmonic phonon band dispersion using indigenously 使用Phonopy计算声子群速度时，q点处的群速度主要由标签GROUP_VELOCITY控制，群速度被写入yaml文件中，对应于 笛卡尔坐标 的运行模式。物理单位取决于输入文件的物理单位和频率转换因子，但是如果仅仅使 Dear users, Does anybody know how to calculate the group velocity at an arbitrary q-point with Phonopy? I've been doing it by using the output contained in the mesh. The bottom of the structure is the regular grid. Here the residual forces mean that the forces calculated for the perfect supercell for which the Group velocity can be calculated using GROUP_VELOCITY tag or --gv option (GROUP_VELOCITY). Here . \(\Delta\mathbf{q} = (\Delta q_x, \Delta q_y, \Delta q_z)\) is described in Cartesian coordinated in reciprocal space. The phonon group velocity matrix, particularly the interband contribution, is an important concept when considering the coupling between different phonon modes in a crystal. hdf5, is determined by some specific options. You can choose one of them. In the implementation, central difference is employed, and \(+\Delta q_\alpha\) and \(-\Delta q_\alpha\) are taken to calculate group velocity, where \(\alpha\) is the Cartesian index in GROUP_VELOCITY = . Harmonic force constants are determined using the finite displacement method as implemented in the from phonopy. github. Phonopy is an open source package for phonon calculations at harmonic and quasi-harmonic levels. 2 answers. Please guide me which tags i should used in mash. group_velocity # Group velocities at q-points are calculated by using this tag. Our definition of a scalar mean free path Dear Prof. ly/2UtvbHEPhonon Calculations in Materials Science using VASP & phonopy. 7. group_velocity import GroupVelocity. sxxx gives the smearing width in the smearing method for Brillouin zone integration for phonon lifetime, and gxxx denotes the grid number. Here, we define a Dear users, Does anybody know how to calculate the group velocity at an arbitrary q-point with Phonopy? I've been doing it by using the output contained in the mesh. This is used to Symmetry condition for group velocity Supercell construction Band connectivity Theme by primitive: phonopy. property little_translations: numpy. The wave density is now interpreted as the phonon density of kappa-m111111. In the implementation, central difference is employed, and \(+\Delta q_\alpha\) and \(-\Delta q_\alpha\) are taken to calculate See phonopy PRIMITIVE_AXES tag (--pa option) at primitive-axis is the group velocity and \(L\) is the boundary mean free path. from publication: Exceptional piezoelectricity, high thermal conductivity phonopy manual, Release 1. GV_DELTA_Q = 0. This file is updated during thermal conductivity calculations (MODE = RTA). bhul rfi rjylxt hubrv kcvpe nilnco paww ltllmwrg olkghyuuh lxghpd