Questions tagged [vasp]

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

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8
votes
1answer
141 views

Electron Affinity of Semiconductors via DFT

Can we calculate electron affinity of a semiconductor (e.g., for Si) using density functional theory calculations in VASP? Which calculations are needed to compute electron affinity and band offsets?
11
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1answer
97 views

Binding energy calculation for Zn atom on armchair graphene slab?

I am trying to repeat the result of this paper for Zn absorbed on the armchair graphene slab. The relaxed top and side structures are the following: The relaxed structure is almost the same as the ...
9
votes
1answer
175 views

How to set vacuum space for slabs?

Let's say I want to work with the slabs, and I want to add 20 Angstrom vacuum space. Do I need just to set lattice parameter c=20 and k-point 1 in this direction?
9
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2answers
81 views

Suggested cutoff for high level VASP calculations

I am new at VASP, and apparently, cutoff convergence is not something like kpoint convergence. Is using ENCUT=1.5xENMAX can be justified? For RPA, GW and MP2 ...
7
votes
1answer
245 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 ...
8
votes
1answer
109 views

How to create an effective INCAR setting in VASP for a heterostructure calculation?

I am a beginner using VASP to do material modeling. I have made a heterostructure model written in the form of a POSCAR file. But the supercell is too big (it contains 60 atoms) so that the ...
8
votes
1answer
75 views

Why are there some residual magnetic moment on the zigzag graphene nanoribbon passivated with H atom?

I am considering the relaxation for the following zigzag graphene nanoribbon. Here the boundary of the zigzag graphene(C: brown) nanoribbon has been passivated with one H atom. I have performed the ...
11
votes
1answer
191 views

What's the crystal orbital Hamiltonian population?

What's the crystal orbital Hamiltonian population (COHP) or the crystal orbital overlap population (COOP)? What's the relation between the bandstructure or density of states (DOS) and COHP/COOP? Why ...
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'...
10
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0answers
105 views

I have access to 1000 cores across 10 nodes, what would be the best way to prallelize an MP2, GW, or RPA calculation for a periodic system in VASP? [closed]

What's the best way for parallelization in VASP for periodic systems? In the documentation, it mostly explains it for the local computer and molecule calculation. Apparently, these explanations don't ...
11
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0answers
116 views

Inconsistent data of chemical potential from different papers

I am looking for chemical potential from literature.$^{1,2}$ I compared the method and data they provided. They use the Fitted Elemental Reference Energy method via GGA+U on VASP employing PAW. U ...
8
votes
2answers
232 views

acceptable range of stretching of a lattice unit cell when we do the heterostructure

Currently, I have to put two different materials together to form a heterostructure. I've already transformed the unit cell of material A from trigonal to cubic. Now the unit cell has a rectangular ...
7
votes
1answer
56 views

Different energies for two different geometries where only the monolayer c lattice constant is different?

I carried out a simple single-point PBE calculation on two different graphene monolayers (only c is different) using VASP with 12x12x1 k-grid. Geometry 1: ...
10
votes
2answers
85 views

Choosing RAM, CPU time, # of cores, and other parameters for an MD run

I did an AIMD run in VASP using 64 cores (32 cores/node) and 250 GB of memory (125 GB/node) for 5 ps (1 fs time step). The calculation took 12.6 hours to complete. CPU efficiency was 99.7% and memory ...
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 ...
10
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0answers
165 views

Constraining coordination or bond lengths for certain atoms in VASP

I have a structure composed of many MX4 tetrahedral units. When doing MD on this structure I find that just one M atom moves into a trigonal planar coordination (MX3). I was wondering how to set ...
9
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2answers
213 views

Problem related to the calculation of elastic constant with VASP5.4.4

I am using VASP5.4.4 to calculate the mechanical properties of the cubic phase SnTe. The structure can be found in the materials project website. In detail, I use the following INCAR to calculate the ...
8
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2answers
115 views

Evaluate the orbital magnetic dipole moment within the PAW sphere

In general, the orbital magnetic dipole moment operator is defined as: $$- {e\over2} \mathbf{r \times v} \tag{1}$$ $\mathbf{v=p}/m$ is true only for simple Hamiltonian like $-1/2\ \nabla^2+V$, but not ...
5
votes
1answer
216 views

How to implement scissor-correction in VASP to study optical properties?

It is mentioned here that It is possible to correct for the DFT band gap error by introducing an empirical scissors correction, which is effectively a rigid shift of the conduction band with respect ...
7
votes
2answers
166 views

How to start with biaxial tensile strain and compressive strain in TMDCs using VASP?

Good morning! I would like to test the biaxial tensile strain and compressive strain in a hexagonal material from the TMDC group (for example HfS2). How to get it into VASP? What are the best ways to ...
4
votes
1answer
228 views

Best practice(s) for q-points convergence in phonon density of states calculations

The answer can be a complete description of all the things we must be attentive to while converging q-points. A peculiar thing that I feel contradicted about: Generally, we don't take an equal # of k-...
8
votes
1answer
132 views

Should all q-points in the first Brillouin zone be sampled in phonon density of states calculations?

For electronic density of states (DoS) calculations with VASP, it is recommended that VASP's internal symmetry routine is turned ...
12
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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 ...
8
votes
1answer
366 views

How to perform virtual crystal approximation calculations in VASP?

Can someone share appropriate tags and methods to perform virtual crystal approximation calculations in VASP?
9
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2answers
118 views

Incorporation of empty d-electrons of a p-block element in calculations in VASP?

Is it possible to incorporate the empty d-orbitals of a p-block element (suppose it is chlorine) into a VASP calculation? If yes, what is the standard procedure to incorporate these orbitals.
9
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1answer
291 views

AIMD and velocity scaling in VASP

Typically one does velocity scaling to "heat" their sample with MD. How do we do this in VASP? Is it by setting the SMASS=-1 and ...
11
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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
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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 ...
7
votes
2answers
73 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 ...
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 ...
13
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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)?
11
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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 ...
8
votes
2answers
127 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 ...
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 (...
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?
9
votes
2answers
280 views

How to make a good HSE06 bandstructure for TMDC monolayer material (e.g.: WS2) in terms of VASP calculation INPUTS?

I want to perform HSE06 band-structure calculation of a WS2 monolayerwhich has the following POSCAR with ...
9
votes
3answers
674 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 ...
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 ...
10
votes
1answer
174 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? ...
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 ...
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 ...
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 ...
10
votes
1answer
119 views

What resources are available to learn how to do something in VASP?

Apart from what is obvious (from a Google Search), what are the various resources available if I want to learn how to do something in VASP (for example, starting an HSE06 calculation)?
7
votes
1answer
173 views

Why is VASP so popular for 2D materials?

I have seen that in many articles of 2D materials calculations that VASP is the most used one among DFT codes. Could please explain to me why?
6
votes
1answer
155 views

How to create a POSCAR for hexagonal structure for VASP calculations?

The method that I am following in creating a hexagonal lattice POSCAR file is by downloading it from https://materialsproject.org/ website. Now, I want to learn how to create it manually starting from ...
8
votes
1answer
251 views

How to extract lattice constants a and c from relaxed hexagonal structure using VASP?

Taking a bulk WS$_2$ (bilayer) structure and relaxing it with ISIF=3 and IVDW=10 (DFT-D2 method) using the VASP code. Then ...
5
votes
1answer
100 views

Best vdW correction functional for transition metal dichalcogenides

For relaxation of transition metal dichalcogenides (e.g.: WS2) using the VASP code, what is the best choice for vdW correction method (e.g.: DFT-D2, DFT-D3 or optB88-vdW) that can give you good ...
11
votes
1answer
279 views

Simulated low energy electron diffraction (LEED) patterns

What modern software supports the generation of LEED patterns? It seems most LEED simulation packages are quite old and do not work on modern hardware. Is there something that prevents common ...
7
votes
1answer
71 views

Work Function Problem

2D materials (such as graphene) are mostly exfoliated from their 3D bulk counterpart. I am wondering how we can calculate work function for a 2D material? Normally electrostatic potential in the out-...
10
votes
1answer
76 views

Edge states in Topological Semimetals

Does it make any sense to calculate edge states for topological semimetals while they don't have any global gap?