Kpar cores time s speedup 1 64 293 64 2 128 159 118. I do this by varying the k points number n x n x 1 and getting the energy. The first brillouin zone is the locus of points in reciprocal space that are closer to the origin of the reciprocal lattice than they are to any other reciprocal lattice points see the derivation of the wignerseitz cell. The kpoints at which the brillouin zone is to be sampled during a self consistent calculation to find the electronic ground state may be defined either by specifying a list of kpoints or a monkhorstpack grid in terms of the dimensions of the kpoint mesh or a minimum kpoint density. Previously, i tested the k point parallelization scheme in vasp 5. The number of k points in the returned grid will scale roughly as mindistance d, where d is the number of periodic dimension e. Software codes here is a list of software codes that may be used to perform the sort of research of interest to the psik community. The term monkhorstpack kpoint set is used to describe a regular grid of kpoints.
For fccbcc and sc a containing 31 k points is reduced to 56 k points in the irbz. Kpoint parallelization in vasp, part 2 peter larsson. For some software packages this is an important remark, for other. Quastion about kpoints and energy cutoff physics forums. Indeed, in most cases, parallelising over kpoints can introduce a very poor loadbalance, unless the number of individual kpoints far exceeds the number of. The origin of the monkhorstpack grid may be offset by a. I already have the poscar and sposcar and so am not worried about it. Everybody is welcome to have a look, but posting questions and. Any dft algorithm should aim to reach only the ground state and no excited state. Another definition is as the set of points in kspace that can be reached from the origin without crossing any bragg plane. Of course you can always use more k points to test k point convergence. It does not work as well for metals, for example, you cannot expect to run a small metallic cell with thousands of k points efficiently on compute nodes. Probably others have run periodic dft calculations on water you could find out in. The approach implemented in vasp is based on a finitetemperature localdensity approximation with the free energy as variational quantity and an exact evaluation of the instantaneous electronic ground state at each mdstep using efficient matrix.
User notes for vasp laboratory computing resource center. Use of symmetries allows treatment of only symmetry inequivalent k points and reduces computation. You can refer to the vasp manual to find more information 2 energy cutoff has nothing to do with k point. An mp grid is thus specified by just three numbers, the number of points along each. Vasp is a complex package for performing abinitio quantummechanical molecular dynamics simulations using ultrasoft vanderbilt pseudopotentials uspp or the projectoraugmented wave method paw and a plane wave basis set. The path is unique for each of the 14 bravais lattice types and, as such, will depend on the symmetry of the unitcell. It can also expand a regular grid specification generally misnamed a monkhorstpack grid to an explicit list of k. Vasp or an external tool called k points can calculate regular k meshes automatically see next section generating an output file ibzkpt which has a valid. Wavefunction of co molecule 1 check the band structure or ibzkpt file to check which k point do you want to plot. Everybody is welcome to have a look, but posting questions and answers is reserved for licensed user only. Kpoints automatic generation mp scheme 0 monkhorstpack 8 8 6 0 0 0 define the path of kpoints along which band structures are calculated.
It works best with mediumsized hybrid calculations, where you have a few k points and a lot of computational work per k point. Vasp performs ab initio quantum mechanical molecular dynamics md using pseudopotentials and a plane wave basis set current release 5. It can read kpoints from a check or cell file, and output them into a new cell file. If the second line equals zero, kpoints are generated automatically using the monkhorst. Type silicon in the filter field at the top and select silicon alpha in the list. The selection of mindistance r min in our paper determines the density of the k point grid generated. One of the best known and widely used software for performing this type of calculation is the vienna ab initio simulation package, vasp, which currently offers a. Vasp is a package for performing abinitio quantummechanical molecular dynamics md using pseudopotentials and a plane wave basis set. The selection of mindistance r min in our paper determines the density of the kpoint grid generated. In vasp, how do we determine the best number of k points for. For bandstructure calculations, provide a list of kpoints, see example kpoints for bandstructure lgxu kg 10 line reciprocal 0. Nevertheless this method for providing all k point coordinates and weights and possibly the connection lists is also important if the mesh contains a very large number of k points. What is the kpoints in electronic structure calculations.
For fccbcc and sc a containing 31 kpoints is reduced to 56 kpoints in the irbz. If you are interested in inspecting the actual python script, you can now send the scipt to the editor. Introducing kpoint parallelism into vasp sciencedirect. Im a vasp beginner and not really sure how to fix this.
Define the points vasp uses to sample the first brillouin zone in reciprocal space. New features and releases, bugfixes, highlighted papers, and more. Amarnathhvaspa the worlds leading software development. Iidft and vasp software input files kpoints several methods according to the expected property kpoints along high symmetry lines 10 linemode rec 0 0 0. In the quantumatk main window, click on the icon to open the builder go to the stash, click add. The number of k points in the irreducible part of the brillouin zone irbz might be much smaller. Vasp or an external tool called kpoints can calculate regular kmeshes automatically see next section generating an output file ibzkpt which has a valid.
In solidstate theory kspace is often used to mean reciprocalspace in general, but in electronicstructure theory kpoints have a much more specific meaning. To get the best performance, we recommend you select a value of mindistance carefully. In vasp, how do we determine the best number of k points for dos. Bash scripts for automating scf calculations, optimizing encut, kpoints and lattice parameters required for carrying out vasp calculations. Optimised lattice geometry is located in contcar file and generated kpoints grid is in ibzkpt file. In other words, the kpoint pattern of a smaller brillouin zone which would correspond to a larger unit cell in real space is unfolded in the brillouin zone of your. The k points at which the brillouin zone is to be sampled during a self consistent calculation to find the electronic ground state may be defined either by specifying a list of k points or a monkhorstpack grid in terms of the dimensions of the k point mesh or a minimum k point density. For bandstructure calculations, provide a list of k points, see example k points for bandstructure lgxu k g 10 line reciprocal 0. Check2xsf can perform some manipulations of kpoint data.
December 2016 the delocalized physicist danny vanpoucke. For vasp and insulator calculation, 444 might be good enough. Vaspkit is a pre and postprocessing program for the vasp vienna ab initio simulation package code. The file kpoints must contain the kpoint coordinates and weights or the mesh size for creating the kpoint grid. Calculate the band structure of a crystal quantumatk q. There are three vasp binaries for each architecture vaspgam gammapoint only, vaspstd multiple kpoints and vaspncl noncollinear spins.
Now, vaspkit can only output wavefunction for specified one k points and one band at one time. Indeed, in most cases, parallelising over k points can introduce a very poor loadbalance, unless the number of individual k points far exceeds the number of. Another definition is as the set of points in k space that can be reached from the origin without crossing any bragg plane. In vasp, how do we determine the best number of k points. Vaspkit is written by fortran and also call some python scripts, used under linux environment. Paul kent who implemented the scheme in vasp suggested that it would be more instructive to benchmark medium to large hybrid calculations with just a few kpoints, since this was the original use case, and consequently where you. Previously, i tested the kpoint parallelization scheme in vasp 5. I read in the vasp manual that it should require more k points, but how should i know how many is enough. The latter calculation was performed over 360 processors on the hector phase 2b system, with a speedup factor of approximately compared to the standard version running on 24 processors ideal. I still dont really understand kpoints all too well, i understand fourier transforms and get theyre kinda related to fourier transform of the space and therefore periodicity. May 02, 2014 1 if using pseodupotential, then less k points can be used as compared with allelectron calculations. An mp grid is thus specified by just three numbers, the number of points along each axis, although conventionally there is also an.
In this paper, the program irvsp is developed based on the crts on the bcs for the vasp package 42. Vasp is subject to license conditions that restrict its use. The term monkhorstpack k point set is used to describe a regular grid of k points. When the shift of monkhorstpack kpoints method in qe or. Nevertheless this method for providing all kpoint coordinates and weights and possibly the connection lists is also important if the mesh contains a very large number of kpoints. One of the software packages that uses dft to solve the. Due to our strong engineering domain expertise, we have better understanding of requirements of engineering industry, and are best suited to craft custom software solutions to effectively address those. If the second line equals zero, k points are generated automatically using the monkhorstpacks technique first character in third line equals m. To sum several k points or seting the energy range, vasp partial charge calculation can do it. This is a relatively modest value compared with the values used in conjunction with lmto packages using linear tetrahedron method.
The number of kpoints in the irreducible part of the brillouin zone irbz might be much smaller. Links to home pages are given where possible, together with a short description and some details about licensing. It does not work as well for metals, for example, you cannot expect to run a small metallic cell with thousands of kpoints efficiently on. If i am wrong, can anyone please send me the correct link. Calculate the band structure of a crystal quantumatk q2019. A second question also may seem trivial, sorry about that. As there are several definitions and nomenclatures used in the literature, sumokgen. I also know i only need one in my z direction, however im unsure about the xy planes. Bash scripts for automating scf calculations, optimizing encut, k points and lattice parameters required for carrying out vasp calculations. In solidstate theory k space is often used to mean reciprocalspace in general, but in electronicstructure theory k points have a much more specific meaning. It works best with mediumsized hybrid calculations, where you have a few kpoints and a lot of computational work per kpoint. I have read the paper of monkhorstpack method and the cc method,and in my understanding the shift of kpoints in monkhorstpack method with the parameter ni which chose to be even, is to avoid the gamma point or the kpoints on the boundary,and the point of gamma and the points on the boundary is high symmetry point,so there is degeneracy,and the degeneracy means extreme points,and the mp. Vasp solutions is promoted by us graduates with vision to deliver quality software solutions at competitive price to the engineering world.
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