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27 votes

Quantum ESPRESSO vs VASP

I will try my best to delineate the differences between VASP and Quantum Espresso, specifically, how one has an edge over the other in certain aspects. I will not try to explain the similarities ...
Xivi76's user avatar
  • 2,352
27 votes
Accepted

How to master Fortran with minimal effort?

"How to master Fortran programing with minimal effort?" The concept of "mastering" a programming language is a bit subjective, and people typically don't "master" a ...
Nike Dattani's user avatar
  • 34.7k
26 votes
Accepted

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

There isn't a single correct answer to this question, and it depends on what is slow, what kind of material you are modeling, and what you are trying to calculate. This answer is mostly going to be ...
Andrew Rosen's user avatar
  • 7,301
25 votes

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

This is a good question. In general, it often may not matter too much, but as with all aspects of numerical convergence, the only way for you to know for sure is to investigate. The concise answer is ...
Andrew Rosen's user avatar
  • 7,301
22 votes

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

Here is an excellent answer by Andrew on pre/post processing tools available for VASP. I will introduce another tool I have used for plotting bandstructure and DOS. PyProcar is an open-source Python ...
Thomas's user avatar
  • 8,952
20 votes
Accepted

Quantum ESPRESSO vs VASP

There is another (good) answer, and since I can't comment yet I will add a few things, possibly from a different perspective as someone who uses QE more often. In general, QE is a free (GPL 2.0), ...
Kevin J. May's user avatar
  • 3,121
20 votes

How to master Fortran with minimal effort?

Fortran is a language that evolved strongly and a programmer just maintain very old legacy codes will have very different needs from a programmer maintaining codes written in Fortran 95 and different ...
Vladimir F Героям слава's user avatar
18 votes
Accepted

Is LDA better than GGA for elastic constants?

I don't think you will find a reference showing that LDAs are better than GGAs for computing elastic constants. More specifically, I don't think a paper could reasonably offer an explanation of why ...
Tyberius's user avatar
  • 15.4k
18 votes
Accepted

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

Another option is Sumo, which is a Python toolkit for plotting and analysis of ab initio solid-state calculation data. It supports VASP, CASTEP and Questaal. Plotting is mostly done through a command-...
bzbzbz's user avatar
  • 701
16 votes
Accepted

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

I can't answer in the context of DFT/VASP, where these terms might have specific uses, but I can offer some general comments. These terms are not necessarily mutually exclusive: Total energy probably ...
taciteloquence's user avatar
16 votes

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

Pseudopotentials (PPs) describe the effective interaction between the valence electrons and a nuclei screened by frozen core electrons. This approximation makes DFT calculations less computationally ...
benshi97's user avatar
  • 408
15 votes
Accepted

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

The Atomic Simulation Environment (ASE) is a pretty big name missing from your list. It can read in a variety of VASP-generated output files and do several post-processing analyses. More importantly, ...
Andrew Rosen's user avatar
  • 7,301
15 votes

How do I search for a particular string in Linux?

The OUTCAR is a text file. Therefore, you can use the grep command to grab what you want to search for. Print the current line: ...
Jack's user avatar
  • 14.9k
15 votes

Doubt about energy convergence with different k points

Let's just remind ourselves what k point sampling is. It is used to approximate the integral of a function over the Brillouin zone by replacing the integral with a sum over a finite number of points: $...
Ian Bush's user avatar
  • 775
15 votes
Accepted

How can I use a GUI on a supercomputer?

I prefer to just download the data from the remote disks and then do the plots on my own local machine, which has all of my favorite tools for post-processing my data. I understand that this can be ...
Nike Dattani's user avatar
  • 34.7k
14 votes
Accepted

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

The reason why graphene has Dirac points at K and $-$K is because of a combination of time reversal and inversion symmetries. Therefore, if you impose these symmetries in your VASP calculation, there ...
ProfM's user avatar
  • 11k
14 votes

How can I visualize the trajectory of a VASP simulation?

ASE You can use ASE environment to visualize, it has different options as well. e.g., you can use this command: ase gui vasprun.xml
Shahid Sattar's user avatar
14 votes

How to carry out HSE06+SOC band structure calculation using VASP?

I assume that your structure is fully relaxed. (I) Self-consistent field calculation at DFT-PBE level with spin-orbit coupling (SOC) to obtain the converged charge density. ...
Jack's user avatar
  • 14.9k
14 votes

How do I search for a particular string in Linux?

Use rg If you have a significant size file or file(s) to search, do yourself a favor and choose one of the many significantly faster alternatives to ...
Johannes Pille's user avatar
14 votes

How to master Fortran with minimal effort?

The answers provided by others are excellent and rather comprehensive. I would only introduce a few other resources that could help you down the road to find answers to problems more efficiently. ...
Scientist's user avatar
  • 241
14 votes

How to master Fortran with minimal effort?

I've done that professionally. In the early '90's, I worked at IBM and spent some time porting FORTRAN "codes" to work on the new RISC SYSTEM / 6000. I found that FORTRAN was such a simple ...
JDługosz's user avatar
  • 241
14 votes

How can we calculate the Gibbs free energy from first principles?

To extend your 0K energies to finite temperature, you essentially need to add up the different sources of entropy. Some examples as reviewed by Hickel et al. [1]: Vibrational entropy (usually split ...
Brandon Bocklund's user avatar
13 votes

Semi-infinite surfaces for adsorption: a valid approach?

Is it worth performing a series of convergence tests on the number of layers frozen, as well as the number of layers themselves? I can imagine this would become quite time consuming. Yes, it is ...
Andrew Rosen's user avatar
  • 7,301
13 votes
Accepted

Ab initio molecular dynamics to check material stability at finite temperature

This is a description of some methods available to study dynamical and chemical stability, not limited to MD: Dynamical stability. The question here is: given a compound in a particular structure, is ...
ProfM's user avatar
  • 11k
13 votes
Accepted

mBJ-LDA band structure calculation using VASP

Here I will take Mg3Sb2 from Materials Project as an example to demonstrate the bandstructure calculation flow with the MBJ method. (I) structure relaxation (II) PBE band calculation based on the ...
Jack's user avatar
  • 14.9k
13 votes
Accepted

Geometry optimization for n-layers in VASP

What is the best way to optimize monolayer geometry in VASP? For the geometric optimization of the monolayer in VASP, you should use the following key tags: ...
Jack's user avatar
  • 14.9k
13 votes
Accepted

Parallelization in VASP

As someone that has done a lot of benchmarking for VASP, I would suggest you try the experimental approach. I do believe VASP will add additional bands for you if need be for parallelization, so I ...
Tristan Maxson's user avatar
13 votes

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

Due to the enhanced coulomb interaction and the quantum confinement effect in the two-dimensional limit, the optical properties should be investigated with the GW+BSE method. The practical calculation ...
Jack's user avatar
  • 14.9k
13 votes
Accepted

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

Here I provide an example with my own python scripts to realize your purpose rather than using Pymatgen (You can save data firstly with Pymatgen and plot with python). I assume that you can perform ...
Jack's user avatar
  • 14.9k
13 votes
Accepted

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

Changing ALGO should make no difference in an ideal world. However, when you invoke spin polarization, you may find a different magnetic state from both algorithms. The best practice would be to ...
Tristan Maxson's user avatar

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