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11 votes
Accepted

Does the size of atoms influence the speed of DFT calculations when comparing systems with almost the same number of atoms

For local basis set software, the size of the atoms should not affect anything, only the number of electrons; however, I note that your example software tags (VASP and QE) are plane-wave based. In ...
Phil Hasnip's user avatar
  • 7,907
7 votes

What's the temperature of the output electronic properties get from Quantum Espresso/VASP, even if we use 298 K cell info (atom position) as an input?

This is slightly difficult to answer, since temperature has several effects and in DFT these can be accounted for in different ways. Probably the main four direct effects are: Thermal expansion (or ...
Phil Hasnip's user avatar
  • 7,907
6 votes

How to get 192 of CeO2 atoms coordinates using Vesta?

The paper you link to identifies 4 Ce atoms and 8 O atoms per unit cell, which has the correct stoichiometry and seems a reasonable density for CeO2, so what is going wrong? The issue is that you have ...
Phil Hasnip's user avatar
  • 7,907
6 votes
Accepted

Elastic property in Voigt, Reuss and Hill approximations

Voigt and Reuss bounds are considered as limits within which the polycrystalline elastic modulus can exist. Many other bounds have been proposed subsequently to bridge the gap between theoretical ...
Pranav kumar's user avatar
  • 4,243
5 votes

Convergence Issues in VASP Relaxation Calculations

The problem comes up because you are using such a small EDIFFG, first consider if you really need this small of an EDIFFG. If so, you can try the following. Lower POTIM, likely <0.01 Use an ...
Tristan Maxson's user avatar
5 votes
Accepted

Significant external pressure in non-SCF calculation results

The energy, pressure, forces etc are only accurate for a converged K-point grid. When you do a band structure calculation, you are sampling a tiny subset of reciprocal space and e.g. pressure will ...
Tyler Sterling's user avatar
5 votes
Accepted

problem calculating formation energy per atom using vasp

To put it simply, your code has some issues. It doesn't calculate the formation energy per atom. Basically, what you did is: ...
Abdul Muhaymin -Free Palestine's user avatar
5 votes
Accepted

Calculating structural stability of a doped plane

You should always relax your structure fully when calculating stability, which includes lattice parameters; however, for a 2D plane you only want to relax the in-plane lattice parameters. If you relax ...
Phil Hasnip's user avatar
  • 7,907
5 votes
Accepted

How to check whether spin orbit coupling is strong or weak?

In quantum mechanics, energies associated with coupling, just like energies in other settings, are assessed based on how they compare to other energies. For example, inserting a spin-orbit coupling ...
Nike Dattani - No Free Time's user avatar
4 votes
Accepted

Energies from single points vs. AIMD for training Machine Learning Force Fields

In the shortest way possible, temperature cannot be defined for single-point calculations. This is because temperature arises from the kinetic energies of the atoms or ions (nuclei), and a single-...
Andrey Poletayev's user avatar
3 votes

How to make Quantum espresso input file from Vesta?

I exported to POSCAR from VESTA ...
Pranav kumar's user avatar
  • 4,243
3 votes

Finding Octahedral and Tetrahedral sites

In order to obtain the atoms' coordinates from Pd (110) plane, you need to start with an initial crystal structure. XYZ files doesn't have the information for ...
Camps's user avatar
  • 23.4k
2 votes

Can lattice vectors have negative components for DFT calculations?

One should not change lattice vectors based on their signs if they originate from standard programs (here VESTA). We tend to prefer simple and positive lattice vectors, but a simple cubic system with ...
nickpapior's user avatar
  • 3,494
2 votes

Why is the SCF calculation performed after VC-RELAX more energetically stable than the VC-RELAX calculation in QE

Most likely this is because your basis set is different before/after a variable-cell relaxation. The size of your basis set (i.e. number of planewaves) depends on the size of the unitcell: at fixed <...
Tyler Sterling's user avatar
1 vote

How to make Quantum espresso input file from Vesta?

Step1: Save the file as a CIF file: Save as> Choose .cif extension. Step2: Install cif2cell: pip3 install cif2cell Step3: ...
Atom's user avatar
  • 1,005
1 vote

Is it possible to build a force field that suits all elements based on VASP's machine learning result?

Since this question was asked, several all-elements, or "universal", machine-learning force fields have been published. These include M3GNet, CHGNet, and MACE. Several semi-universal force ...
Andrey Poletayev's user avatar

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