Questions tagged [k-points]
Questions regarding k-points in crystal geometric settings.
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BZ grid and susceptibility for numerical Pauli limit calculation
I am trying to calculate the Pauli limit for a superconducting material with Hamiltonian $H_0$ and an external magnetic field contribution $H_p$. I find the matsubara greens function as $\hat{G} = [i\...
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supercell nscf kpoints for optical properties
I am calculating the optical properties of 200 atoms supercell with quantum espresso. What is the approximate number of the nscf kpoints (nk nk nk)should I start with, to avoid lengthy kpoints ...
- 161
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About high-symmetry points in the first Brillouin zone of space group R-3m
I want to figure out the high-symmetry points in the first Brillouin zone of space group R-3m (166). For example, there are points K and M just like the bandstructure in this paper.
But I can't figure ...
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Number of k-points for unit and super cell
I am just new with solid state calculation and would like to know one thing.
Why is plane wave basis set is good for 1s and 2s orbitals, but for higher convergence is poor? Why is it better to use ...
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Inconsistent band structure of bilayer graphene
Context
I am performing band structure calculations for bilayer graphene using QE codes. I used X-crysden for the k-point mesh ...
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Graphene Band Structure with SIESTA
I am struggling with getting a correct band structure for even pristine graphene using SIESTA. The issue is almost certainly the K point path. My graphene sheet (128C atoms) isn't the traditional ...
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What are the general principles of setting parellelization options in VASP?
I am doing the computation of a perovskite system of 20 atoms in a supercell.
I know that options like NPAR and KPAR, and the numbers of cores used for computations can greatly affect the efficiency, ...
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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 ...
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1
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PyProcar bands plot error
I am new to using PyProcar and am getting the following error when trying to plot band-structure using it:
Here is my input:
...
4
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2
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What's the meaning of k-points with weight zero?
In a post from the Quantum Espresso mailing list, a user suggests adding k-points with weight zero to an SCF calculation as a workaround to allow bandstructure to be computed using a hybrid functional....
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Can someone guide me on how to get the k-point file for a VASP simulation?
I have a system with box dimensions of 21.0 * 21.0 * 80.0 for x,y and z directions. How may I generate the KPOINTs mesh for this system for VASP simulation? Any reference on this is hugely appreciated....
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How to add a break into CASTEP k-point path
I am trying to produce a band structure for TiO2, with the cell file shown below:
...
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Confusion regarding specifying a k-point path for phonon dispersions/bandstructure plots
I have been trying to obtain a plot of the phonon dispersion of a BCC metal using Quantum Espresso. In the literature it seems that a commonly reported path is ...
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Gamma-only error for electrode in a device calculation
I am using SIESTA 4.1.5 version,
I have done electrode Calculation using K-grid values 3X3X100 for both the electrodes, and
currently i am doing transmission calculation, I tried different K-grid ...
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How to generate k-point grid using Quantum ESPRESSO?
I am doing an exercise to calculate silicon crystal mobility using quantum ESPRESSO.
I'm in a step where i should do a non self-consistent calculation on a 6x6x6 uniform and Γ-centered k-point grid ...
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I'm considering to take an introduction course with textbook "Materials Science and Engineering: An Introduction", as a beginner QE user. Is it okay?
People, I am a beginner in material modeling (I am studing solid state in Quantum ESPRESSO) and I am having a lot of difficulty with basic terms like "k-points", "Miller Indices", &...
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k-path for phonon band structure
I have observed in research papers that the k-path chosen for electronic band structure and for phonon band structure to be different. I am currently using VASPKIT in order to obtain the path for ...
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How to transform the k coordinate into the k path used in the band structure?
When drawing the band structure, I need to transform the coordinate of k-points into a k-path, but I am not sure what the formula is.
I checked the result of siesta,...
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How do I find out the subdivisions N_1, N_2 and N_3 in BAND STRUCTURE? [closed]
I want to find out how to get subdivisions from vasprun.xml of Brillouin zone. Does anyone know how to do this?
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How to choose K point for a super cell
I have been told to use VASPKIT in order to obtain the KPOINTS, but VASPKIT only works for Primitive cell and I am currently using a super cell. The super cell has a repeated primitive cell about one ...
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Reciprocal lattice and k-lattice belong to different groups in VASP
I am trying to do geometry optimization of TiO2 with VASP.
Here is the POSCAR file, which I get from the Materials Project.
...
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How to find the reduced coordinates of reciprocal lattice vector which defines the kslice plane in first brillouin zone? [closed]
I am trying to get the Fermi contour lines of an FCC crystal system. For this, I am trying to use the wannier90 program. I have already done the wannierzation part successfully. Now I am trying to get ...
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Minimum number of kpoints for calculation of properties of nanoparticles in vasp
I am a little confused about what should be the correct number of kpoints that I wanna use. I am currently working on a small cluster so picking a high value(even around 10) gives me a memory fault. ...
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Why do we need to use fake k-points when doing HSE band structure in VASP?
I want to know why we need fake k-points in HSE band structure calculation? I mean why we can't take a simple high symmetric path like we do in PBE calculation?
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How could I fold a specific high symmetry point to the Gamma point?
How could I get the Brillouin Zone of 2*2 supercell? I tried to use see k-path website, but when I upload a supercell, it still generates the Brillouin Zone of the unit cell.
What I want to do is to ...
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Do the VBM and CBM have to be on the high symmetry point? [duplicate]
I am trying to generate the band structure of a slab, a lot of tutorials tell me that I need to generate the high symmetry K point path, but I am wondering that if the VBM and CBM have to be on the ...
- 1,977
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Physical interpretation of k-points
What is the Physical interpretation of the k-points used in ab initio calculations? Why must the number of k-points be optimized rather than just using some large fixed number of them?
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Doubt about K point selection for 2x2x1 supercell
I have one doubt about K points selection for a supercell. I construct one 2X2X1 supercell with 64 atoms having a=11.19, b=11.19, c=5.59. For checking K points convergence test with energy should I ...
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Generating a Gamma centered uniform k mesh in SIESTA DFT
The SIESTA DFT software provides to incorporate a Monkhorst-Pack k grid in DFT calculations. However to use the results with the BoltzTraP2 software, a Gamma centered k-grid with uniform distribution ...
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Monkhorst – Pack sampling: How many k points one should take
Reference: Density Functional Theory: A Practical Introduction, David Sholl, Janice A. Steckel, Chapter 3, Page No. 59
A useful rule of thumb is that calculations that have similar
densities of k ...
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Doubt about energy convergence with different k points
During the convergence test of k points, I observed my energy start increasing instead of decreasing. I am doubtful is this correct or I am doing something wrong. can I take the appropriate K point in ...
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How to do lattice optimization, encut optimization and Kpoint optimization in VASP?
What is the procedure to do lattice optimization, encut optimization and kpoint optimization in VASP?
Thank you in advance.
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What is the M-point of an orthorhombic crystal structure?
In this paper, they have plotted the band structure of orthorhombic $\ce{CsPbI3}$ using Wein2k. The k-path given here is Γ—X—R—Z—Γ—X—R—A—M—X, but I cannot find the M point in the orthorhombic crystal ...
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Valleys and time reversal symmetry (Zeeman effect)
Right now I'm focused on transition metal dichalcogenides. These compounds in the Brillouin zone have valleys in the valence band and in the conduction band at points K and -K. From what I've seen of ...
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What does occupations='tetrahedra' mean in Quantum ESPRESSO?
I am trying to understand Quantum ESPRESSO input file, line by line. So far everything seems pretty easy to understand. However, I do not know what ...
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How to generate the high symmetry paths for band structure calculations?
Suppose I want to calculate the band structure of a material system along a specific high symmetry path in the Brillouin Zone. If the point group of the system is given, how can I easily compute the ...
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Why is Energy Cut-off and K-Point Convergence necessary in LCAO-based codes like SIESTA?
I am new to DFT-simulation and I wish to understand how it works behind the scene. As the title suggests I don't understand why LCAO-based codes have to define K-points and cut-off energies. I ...
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"A dense k mesh of 40,000 k points was used in the Brillouin zone". How is this number obtained?
In publications, I usually see the statement "A dense k-mesh of 40,000 k-points was used in the Brillouin zone". An example of this is in this paper. But in the paper they have ...
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Number of KPOINTS in irreducible part of Brillouin zone
I want to investigate the comparison of Total Energy per cell with respect to the number of KPOINTS in the irreducible part of the Brillouin zone but I do not know ...
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Does SOC band structure calculations require higher number of k-grids?
In so many papers I see that they carry out soc band structure calculations with much higher kgrid than used for the geometry optimization. Whats the logic behind that?
user1263
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Energy per unit cell in NWChem differs for different supercells despite the same k-points density
I try to compute the unit cell energy of the $\ce{Ti2CO2}$ MXene with NWchem.
Computing the 1x1 supercell with 4x4x1 K-points grid I got -1875 Ha.
Computing the 2x2 supercell with 2x2x1 K-points grid ...
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How to analyze the band symmetry with Quantum ESPRESSO?
This question is related to this paper: J. Phys. Chem. Lett. 2017, 8, 13, 2999–3007
The above figure shows symmetry analysis for the band structure. The author writes:
The band symmetry and parity ...
- 14.9k
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Validity of interpolation for density of states?
A density of states (DoS) curve seems like an example of a curve for which curve fitting doesn't seem to make sense, or does it? How could we interpolate on such a curve, given that we got the curve ...
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Is total energy difference lower than 1 meV/atom good enough for k-point convergence?
How much energy difference could be considered as tight convergence? Is total energy difference lower than 1 meV/atom good enough for kpoint convergence for total energy calculation?
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k-points: Odd vs. Even
As mysterious as k-points are, why is there a cut-off for an odd and even k-mesh preference?
On the VASP wiki page titled, "Number of k points and method for smearing", they say results when ...
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How to know optimal K-points grid values for good DFT calculation?
I am doing DFT calculations with pw.x executable in Quantum Espresso. For this we have to choose right K-points grid in order to perform error-less calculation. But I have no idea about how can I ...
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Monkhorst-Pack, Gamma-centred and gamma only
Sorry if this question is too simple for this community but I still couldn't find an answer to it.
Do gamma-centred and gamma only grid mean the same thing?
If not, what's the difference?
How do they ...
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adaptive k-mesh
Are there any known codes or scripts to generate an adaptive k-mesh for DFT calculations? For example, I'd like to make the k-mesh near the $\Gamma$ point (e.g., half the zone) more denser ($20\...
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Input constraints while comparing different DFT calculated properties for the same material but different atomic arrangement
Let's consider a fictitious AB type binary alloy. AB is known to exist in a B2 type ordered ...
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Increasing supercell size to increase K-points sampling
Suppose I have a system with a property that is highly dependent on the density of k-points, namely the dielectric function. Using a small supercell, say with 4 atoms, I've reached the maximum allowed ...
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