Questions tagged [k-points]

Questions regarding k-points in crystal geometric settings.

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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, ...
蕭力諶's user avatar
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5 votes
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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 ...
Vladislav Gladkikh's user avatar
2 votes
1 answer
79 views

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: ...
DAVID MOROCHO POGO's user avatar
4 votes
2 answers
306 views

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....
Camilla's user avatar
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6 votes
2 answers
326 views

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....
Xdrake's user avatar
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5 votes
1 answer
57 views

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: ...
Rory Ward's user avatar
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6 votes
1 answer
72 views

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 ...
aQuarkyName's user avatar
3 votes
1 answer
156 views

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 ...
Shanmuka Rao's user avatar
2 votes
1 answer
310 views

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 ...
Camilla's user avatar
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3 votes
1 answer
129 views

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", &...
Everson Gomes's user avatar
5 votes
1 answer
135 views

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 ...
Parmeet Singh EP 066's user avatar
6 votes
1 answer
328 views

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,...
Jack's user avatar
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2 votes
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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?
namelessenko's user avatar
7 votes
0 answers
172 views

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 ...
Parmeet Singh EP 066's user avatar
4 votes
1 answer
1k views

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. ...
Jack's user avatar
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5 votes
0 answers
119 views

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 ...
UJM's user avatar
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7 votes
1 answer
289 views

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. ...
Parmeet Singh EP 066's user avatar
9 votes
2 answers
357 views

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?
Himanshu Sharma's user avatar
7 votes
1 answer
345 views

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 ...
Jack's user avatar
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4 votes
0 answers
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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 ...
Jack's user avatar
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15 votes
1 answer
404 views

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?
Maulesh VALA's user avatar
9 votes
2 answers
359 views

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 ...
poonam sharma's user avatar
8 votes
1 answer
179 views

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 ...
PBH's user avatar
  • 2,593
7 votes
1 answer
343 views

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 ...
147875's user avatar
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13 votes
1 answer
689 views

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 ...
poonam sharma's user avatar
3 votes
1 answer
498 views

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.
Maulesh VALA's user avatar
8 votes
1 answer
169 views

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 ...
Wonder's user avatar
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8 votes
1 answer
262 views

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 ...
Carmen González's user avatar
13 votes
1 answer
1k views

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 ...
RedGiant's user avatar
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18 votes
4 answers
3k views

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 ...
beginner's user avatar
  • 181
11 votes
1 answer
1k views

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 ...
Brentdb's user avatar
  • 113
8 votes
1 answer
229 views

"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 ...
Hydrogen's user avatar
  • 159
11 votes
1 answer
564 views

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 ...
Shalini's user avatar
  • 1,575
6 votes
2 answers
103 views

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?
user avatar
4 votes
2 answers
153 views

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 ...
user36313's user avatar
  • 450
11 votes
1 answer
570 views

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 ...
Jack's user avatar
  • 14.7k
10 votes
2 answers
216 views

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 ...
Hitanshu Sachania's user avatar
13 votes
1 answer
453 views

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?
Barix's user avatar
  • 221
8 votes
1 answer
888 views

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 ...
Hitanshu Sachania's user avatar
13 votes
5 answers
7k views

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 ...
UJM's user avatar
  • 2,481
13 votes
1 answer
4k views

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 ...
Bereau's user avatar
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11 votes
1 answer
176 views

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\...
Xiaoming Wang's user avatar
7 votes
2 answers
90 views

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 ...
Hitanshu Sachania's user avatar
12 votes
1 answer
934 views

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 ...
Anibal Bezerra's user avatar
11 votes
2 answers
607 views

Which properties of a material calculated using density functional theory are affected by smearing?

Smearing (smearing width $\sigma$, to be precise) has always been confusing. I understand what it is but can't pin it down when it comes to DFT calculations. Should it be converged like k-points and ...
Hitanshu Sachania's user avatar
9 votes
2 answers
267 views

k-points convergence for spin polarised vs non-polarised DFT calculations

Spin-polarised calculations come at a computational cost and I tend to take ISPIN = 2 only after I'm done with a proper initial relaxation of the structure, so the ...
Hitanshu Sachania's user avatar
7 votes
0 answers
648 views

Calculating band structure with HSE using Open_grid (Quantum ESPRESSO) [closed]

I have executed the SCF calculation and obtained the results. After which I used kmesh.pl to extract k-points. I was able to run wannier calculations but there was an error Checking info from wannier....
Hepsibah Priyadarshini.C's user avatar
13 votes
2 answers
2k views

mBJ-LDA band structure calculation using VASP

I tried to create a band structure with the mBJ-LDA method using VASP. I found information that the KPOINTS file should be created according to the "0-weight (...
Miłosz Rybak's user avatar
11 votes
3 answers
2k views

How to generate KPOINTS file for HSE06 band-structure calculations?

I have had a look at the example of Silicon provided here in the WIKIVASP website, and I noticed that the KPOINTS file used for ...
Chi Kou's user avatar
  • 5,593
10 votes
1 answer
214 views

Is it okay to take a cubic Monkhorst-Pack k-mesh for a non-cubic supercell in a DFT calculation?

Assume that the numbers of k-points in each direction are sufficient. Example - Lengths of lattice vectors: $2\: 2\: 4$ Required k-mesh: $9\times 9\times 5$ Would a $9\times 9\times 9$ k-mesh work? ...
Hitanshu Sachania's user avatar