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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
  • 7,897
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
  • 7,897
6 votes

Should alat value be used as it is in calculation or multiplied with CELL_PARAMETERS value?

alat works like a scale factor. So, as pointed out by naturallyInconsistent, you can use A=5.95*1.07708030 because in QE, ...
Abdul Muhaymin -Free Palestine's user avatar
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
  • 7,897
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
  • 7,897
4 votes
Accepted

Which data files need to be stored after publishing a DFT study?

Gregor Michalicek noted above in a comment, "I suggest you store everything that is needed to reproduce your results. If a file is just temporarily needed by the calculation and not needed in ...
Susi Lehtola's user avatar
  • 19.7k
3 votes

How to make Quantum espresso input file from Vesta?

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

How to calculate the effective mass from DFT band calculations?

Just wanted to mention that the effmass package mentioned above now supports Castep, VASP and FHI-aims. If someone wants to add support for Quantum ESPRESSO via ASE, I suspect it's not too difficult. ...
leopold.talirz's user avatar
2 votes

Has anyone used Critic2 with Quantum ESPRESSO? Need help to determine non-nuclear charge determination

From the Quick Start Guide at Critic2 site: Critic2 reads the user commands from a single input file (the .cri file). A simple input is: ...
Camps's user avatar
  • 23.4k
2 votes

Quantum ESPRESSO: how to calculate mobility?

A simple equation for the electron mobility is $\mu=e\tau/m^*$. Here, $e$ is the electron charge, and the effective mass $m^*$ can be obtained by fitting a parabola to a band minimum/maximum as ...
leopold.talirz's user avatar
2 votes

Phonon calculations related problems

Replying to your comment above: of course you have to converge wrt. q-points! To answer your original question, of course you can calculate at Gamma only with DFPT as long as you only care about ...
Tyler Sterling's user avatar
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
2 votes

Why do certain atoms remain fixed during relaxation?

Usually this happens when the forces on atoms are fixed by symmetry. Consider e.g. the CO2 molecule. If you change the bond-length on both sides of the C atom so that the molecule is still symmetric, ...
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
  • 995
1 vote
Accepted

Unit cell size for phonon modes

can I compare the phonon modes by using unit cells of different sizes? Sort of. The easiest thing to compare is densities of states. You can project it onto atoms to get even more detailed results. ...
Tyler Sterling's user avatar
1 vote

How to plot absorbance from a Quantum ESPRESSO optical calculation using ε1, ε2, and energy data?

What you have done so far is that you now have calculated the real and the imaginary parts of the dielectric functions, which is a function of $\omega$, i.e., $Re(\varepsilon(\omega)) = \varepsilon_1(...
Abdul Muhaymin -Free Palestine's user avatar

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