Questions tagged [vasp]

For questions about use of the Vienna Ab initio Simulation Package (VASP).

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23
votes
2answers
1k views

Quantum ESPRESSO vs VASP

We know that both Quantum ESPRESSO and VASP can perform lots of different kinds of simulations of materials. But what can VASP do that Quantum ESPRESSO can not, and vice-versa?
23
votes
1answer
331 views

What are good ways to reduce computing time when working with large systems in VASP?

I know that parallelization is an important factor, however, I wanted to know if there are any other methods of reducing computing time when dealing with large systems without sacrificing accuracy. ...
19
votes
4answers
384 views

What is the status of graphics processing units in plane-wave DFT?

A few years back, I performed a few calculations of metallic slabs using VASP and the Atomic Simulation Environment (ASE). I'm by no means an expert, but I noticed that the calculations were very CPU ...
19
votes
3answers
235 views

Hexagonal lattice volume EOS fit

I have a little problem concerning hexagonal volume fitting using VASP. I have followed these steps: Relax the structure from a given volume using ISIF =4 Copy ...
18
votes
9answers
8k views

How to master Fortran with minimal effort?

Fortran language is used in many first-principles matter modeling codes, such as VASP and QE. These codes usually include many ...
18
votes
3answers
1k views

k-points and ENCUT convergence tests before or after relaxation?

Let's say I want to relax a structure using VASP. K-points and ENCUT convergence tests must be conducted before or after relaxation? and which tags should be ...
18
votes
2answers
147 views

Calculating binding energy between two systems

Regarding the calculation of binding energy of molecular absorption on graphene, for which this has been discussed before, the process of calculating $E_{AB}$ is fairly straight forward, i.e., it is ...
18
votes
2answers
221 views

Semi-infinite surfaces for adsorption: a valid approach?

I'm currently trying to surface reaction of small molecules on metal oxides in VASP. Several papers I've read have approached surface energy calculations in a variety of ways. I first began looking at ...
18
votes
1answer
273 views

What are the ways to ensure thermodynamic stability of a DFT modelled new structure?

One way of predicting the thermodynamic stability of a DFT modelled structure is to calculate the energy above convex hull, which was used as the criterion in The Materials Project database. For ...
18
votes
1answer
300 views

In VASP, how is the chemical potential of elements calculated?

I would like to calculate the chemical potential of elements having different environmental condition (rich or poor) using VASP. How is this accomplished?
17
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2answers
1k views

What are some good band-structure/DOS plotting tools/styles?

I am currently using p4vasp for drawing DOS and band-structure plots, but it is not much handy in modifying the OUTPUTS. Could you please suggest any other good software or tools for that?
17
votes
1answer
212 views

Difference between potential energy, free energy and Coulomb energy in solid state physics

I often encounter terms such as (Helmholtz, Gibbs) free energy, potential energy and total energy when describing the energy of a physical system at atomic level. Sometimes I stumble upon Coulomb ...
17
votes
1answer
270 views

How does the mBJ potential give an accurate band gap as compared to LDA and GGA?

I am not able to understand the literature on how the modified Becke-Johnson(MBJ)$^{[1]}$ potential gives an accurate bandgap. Can someone please help? Thank you. The formula for the potential can be ...
17
votes
1answer
444 views

Are there problems with the Tran-Blaha modified Becke-Johnson potential (mBJ, a.k.a. TB09) in Quantum ESPRESSO?

I have used the modified Becke-Johnson (mBJ) exchange potential before, as it was developed and implemented in Wien2K by Fabien Tran and Peter Blaha (1). In 2013, Éric Germaneau et al. implemented mBJ ...
16
votes
1answer
291 views

How to separate the data plot for spin up and spin down band structure into 2 different graphs, in Pymatgen?

I am a beginner user of the Pymatgen package. In order to process the data from VASP DFT calculation software, I use Pymatgen to visualize the output band structure. When I do spin polarised band ...
16
votes
1answer
151 views

How to ensure a smooth band structure?

I performed an HSE06 calculations using VASP and the calculated band gap is in good agreement with experiment. However the band is not smooth, with very sharp, zig-zag like features. How to improve ...
15
votes
4answers
2k views

How can I visualize the trajectory of a VASP simulation?

Which software package(s) can be used to visualize the trajectory of VASP MD simulation? VMD claims that there is a plugin to read the VASP output, while in the last version for Linux, I did not find ...
15
votes
1answer
420 views

Why is the band gap of graphene “opened” in this VASP calculation?

I used VASP to do the band structure calculation on Graphene. Originally I would expect that the Dirac cone can be observed in the K point. If we watched qualitatively, we can see this behavior. But ...
15
votes
2answers
778 views

What is the difference between Ultrasoft, ONCV and PAW Pseudopotentials? Which is better for a spin-orbit coupled calculation?

I am trying to do spin-orbit coupled calculations for various topological insulators. I have found papers using Quantum Espresso with ONCV pseudopotentials and papers using VASP with PAW ...
15
votes
1answer
336 views

Ab initio molecular dynamics to check material stability at finite temperature

I completed an ab initio molecular dynamic (AIMD) simulation in VASP for a hypothetical material. The simulation was done for 5ps with 1fs steps and the temperature was set to 300K using Nosé–Hoover ...
15
votes
1answer
328 views

What are the pre/post processing tools available for VASP?

I am aware of pyPROCAR and VASPKIT. Are there any other tools supporting VASP
15
votes
1answer
173 views

VASP Dielectric constants: What potential to use?

I've simulated the dielectric constants using the LEPSILON = .TRUE. tag and the PBE GPAW potentials. A collegue mentioned that for accurate results norm conserving pseudo-potentials are the way to go. ...
14
votes
2answers
189 views

Quantum Dot properties using VASP

We are working on the excitonic properties of cadmium-based Quantum Dots (QD) and QD heterostructures. We have MedeA-VASP and hence we managed to make QD structure. Are QD calculations different from ...
14
votes
1answer
198 views

Standard values for level of convergence

In matter modelling we use self consistent approaches for calculating different properties. Many DFT codes find the ground state of the system by determining total energy self consistently. Going ...
14
votes
1answer
399 views

How to convert from primitive to conventional after structure relaxation?

I did this in VASP but I guess this would be the case for any program. I have a structure that has a cubic conventional cell (a = 9.86 A). I found the primitive cell (a=b=c=6.97, alpha=90, beta=60, ...
13
votes
3answers
519 views

Geometry optimization for n-layers in VASP

What is the best way to optimize monolayer geometry in VASP? Should the same method be used for an n-layer (n=2,3,4,5)?
13
votes
4answers
415 views

How to analyze the space group of a relaxed structure that has fractional site occupancies

I am using VASP package to model a material that has fractional site occupancies. An appropriate supercell (cif) was generated using supercell package and converted ...
13
votes
2answers
477 views

How to start with the optical properties of 2D materials with the VASP code?

I hope you are doing well. I am new to VASP, and my project is "Optical properties of 2D materials on VASP" but I have no idea how to run a simple calculation with VASP. I will be very ...
12
votes
4answers
570 views

How to make a k-point convergence test for a bulk structure with a lower k-point in the z-direction?

Let's say I want to make k-point convergence test for graphite. And let's say it converges at 12x12x4. Do I first need to do a k-point convergence test for equal k-points on xyz directions then make ...
12
votes
2answers
643 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 (...
12
votes
3answers
506 views

External magnetic field in VASP?

I have never found any tags or documentation regarding external magnetic field in VASP but in different well known published articles$^1$, the implementation of the external magnetic field by VASP has ...
12
votes
1answer
181 views

Structure relaxation of a thin film structure in VASP

I have some general questions about doing the structure relaxation of a thin film structure in VASP. I want to study the how the band structure evolves as we increase the number of layers of the ...
12
votes
1answer
254 views

How to visualize spin density isosurfaces?

What is the package used for visualization of spin density isosurfaces in VASP like the ones shown below? A simple example/tutorial would be very appreciated.
12
votes
1answer
154 views

DFT vs tight-binding solutions for a Dirac cone in graphene: Why is the DFT version squeezed?

I'm a beginner at DFT calculations with VASP software. I use it to calculate the band structure of graphene and I obtain the following result: I used it to calculate the band structure of graphene ...
12
votes
1answer
54 views

What does this temperature & total free energy profile mean (obtained from VASP NVT molecular dynamics simulations)?

In order to obtain molecular dynamics (MD) simulations trajectory for computing phonon dispersion relation at finite temperature, I performed NVT MD simulation using VASP for my target system. Here is ...
12
votes
1answer
293 views

Why is the Nonequilibrium Green’s function (NEGF) method for quantum transport not implemented in plane wave codes like VASP and Quantum Espresso?

DFT codes like Siesta, QuantumATK, Questaal, and Smeagol having localized basis sets have NEGF implementations available. But not in plane wave codes like VASP and Quantum Espresso. Why is it so?
12
votes
1answer
148 views

Band structure and density of states disagreement (mp-19092)

My question is both specific and general. While looking through the materials project database I found this entry. The band structure reported and density of states are dramatically different it ...
12
votes
0answers
108 views

Correlation Functions in the Cluster Variation Method [closed]

I've been referring to Dr Mohri's paper [DOI: 10.1007/s11837-013-0738-5] for the cluster variation method (CVM). I wish to calculate the configurational entropy of a binary FCC system. Cluster ...
11
votes
4answers
351 views

Create doped structures to POSCAR files for vasp

I have a perfect supercell structure Ni fcc. And I would like to dope another element O or N with a ratio of O:Ni=8:100 to the supercell of 3x3x3 and find the most stable ordering structure. The ...
11
votes
2answers
264 views

Moving from VASP to CASTEP for bulk crystal and surface calculations

Can someone that works with CASTEP and VASP explain to me how a workflow might change between the two programs? I am very familiar with VASP but have not used CASTEP before. As an example, assuming ...
11
votes
2answers
477 views

Parallelization in VASP

I have a system that has 1 k-point, 54 atoms, NBANDS=152, and NGZ=80. I'm running an AIMD simulation on VASP version 5.4.4 The ...
11
votes
2answers
836 views

When should spin polarized calculations be done?

Should the presence of a d block element in the unit cell mandate the need for performing spin-polarized calculations? I wanted to find out the DOS, PDOS, and the band structure. I'm new to DFT and I'...
11
votes
2answers
349 views

Effect of ISYM tag on Partial Density of States (VASP version < 6)

This is from the entry for LORBIT in the VASP Wiki. For LORBIT >= 11 and ...
11
votes
2answers
151 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 ...
11
votes
1answer
240 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 ...
11
votes
1answer
250 views

Are different eigensolvers consistent within VASP (Algo=Normal vs Fast)

I tried to relax a 4x4x1 supercell of ferromagnetic monolayer material using the default settings (ALGO = Normal) but it didn't converge. So, I switched to ...
11
votes
1answer
214 views

How to start with structural defects in monolayer?

First of all, thank you for your help! You are so helpful every time. I would like to calculate the influence of the structural defects on the electronic structure in the HfS2 monolayer. With VESTA ...
11
votes
1answer
241 views

How to use coherent-potential approximation (CPA) method in VASP?

I found there are very few tutorials regarding how to use the CPA method in VASP. Are there any nice materials available? Also what are the pros and cons of CPA and VCA? If CPA is more reliable then ...
11
votes
1answer
107 views

Charge density convergence within VASP using spin polarized DFT+U

I am noticing a possible convergence problem in a magnetic $U$ system I am studying. In the OSZICAR file I often see the rms(c) value go to about ...
11
votes
1answer
160 views

How many GB of RAM would be needed for VASP to evaluate optical properties of a material?

Even though it is a powerful tool, Quantum ESPRESSO's hardware requirements are very high. For instance, to evaluate optical properties, even for structures with tens of atoms, Quantum ESPRESSO can ...