Questions tagged [plane-waves]

Questions about plane-wave basis sets.

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In plane-wave DFT, what needs to be converged and in what order?

Even though I use some Quantum ESPRESSO specific terminology here, this question applies to any plane-wave based pseudopotential DFT code. We know that before running an actual DFT calculation, a few ...
Abdul Muhaymin's user avatar
4 votes
1 answer
94 views

Plane wave basis functions

When using plane wave basis functions, what is the phase of each plane wave? Should a one-electron wavefunction looks like $\Phi^k_{\beta}(r) = \sum_{G} c^k_{\beta,G}e^{i((k+G) r + \varphi_G)}$ ...
mle's user avatar
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2 votes
1 answer
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Plane-wave basis expansion for periodic material modelling: cutoff energy inequality and number of atoms in the simulation

The calculation of electronic structure of infinite periodic material using Plane-waves is the object of study here. The cutoff energy $E_{cutoff}$ provides information about the accuracy of the ...
mle's user avatar
  • 989
5 votes
1 answer
54 views

Kpt boundaries for cubic supercell

I have a question on how to make a supercell in abinit. I am trying to calculate the EBS of a cubic perovskite supercell (2x2x2 cubic STO). The geometry information can be found on the MP here. I need ...
Marco Di Gennaro's user avatar
3 votes
0 answers
25 views

total spin (J-resolved) projected band structure with SOC

I have been asked by a colleague if it is possible to calculate the spin-projected band structure (with SOC) for a material he is studying. He referenced a paper Boschini et al. Sci. Reports 2015 - ...
Paul Fons's user avatar
1 vote
1 answer
263 views

MPI error in Quantum ESPRESSO during optimization of particularly large molecules

I have been recently trying to optimize a particularly large system Mo2C in QE using the pw.x executable and encountering the following MPI errors: ...
Avrana's user avatar
  • 79
2 votes
0 answers
161 views

Running out of RAM memory in relax calculation using Quantum Espresso [closed]

I am doing a relax calculations of a 160 gold atom cubic cell using 126GB of RAM space on one node using quantum espresso. but the calculations fails with out-of-memory error. I have tried using ...
Pradeep pal's user avatar
3 votes
1 answer
125 views

In a plane-wave code, does the Fermi energy depend on the pseudopotentials used?

I am planning to do some work using grand-canonical DFT, I believe that the Fermi energy depends on the pseudo-potentials used (like the total energy). My understanding is that the Fermi energy has to ...
Okano's user avatar
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7 votes
1 answer
169 views

Mixing pseudopotentials with gaussian and plane wave basis

I am somewhat of a novice in computational chemistry of materials, and have been tasked to replicate simulations from a relevant paper. The paper is a bit scant on details so I am trying to recreate ...
ipcamit's user avatar
  • 535
1 vote
0 answers
239 views

how to choose a basis set when calculating COHP? [closed]

I am trying to use the lobster program to calculate COHP, according to the explanation in the literature, it is better to add unoccupied atom orbitals into the basis set. The initial step in ...
Jack's user avatar
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4 votes
1 answer
263 views

Compute solvation energies with (ESM) RISM-SCF

I want to use the 3D-RISM-SCF and ESM-RISM implementation in Quantum Espresso to compute solvated adsorption energies and absolute solvation energies. Before starting I read the main paper by S. ...
Okano's user avatar
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2 votes
0 answers
130 views

Force convergence in Wannier orbitals based DFT code [closed]

I am working on Pt(111) / nanoparticles with various ligands, I am mainly using two softwares: A well known general purpose plane-wave code (Quantum Espresso). A less known software that is also ...
Okano's user avatar
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9 votes
1 answer
581 views

Simulation of charged species with plane-waves in Quantum Espresso

I am using Quantum Espresso to simulate a platinum surface with ligands, so far everything is working ok. I now need to introduce a solvated hydronium $\ce{H_3O^+(H_2O)_2}$. Is there something I ...
Okano's user avatar
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10 votes
1 answer
1k views

Energy cut-off test meaning in atomic-like basis functions' DFT

I have been using SIESTA code to perform some practicals in my college and I have run energy cut-off tests before calculating properties of semi-conductors or insulator. As far as I am concerned, ...
Paul Logan's user avatar
17 votes
1 answer
459 views

Linearized Augmented Plane Wave Method vs. Pseudopotential Methods

While reviewing some DFT literature, I have come across a few papers utilizing the LAPW (Linearized Augmented Plane Wave) method, but I am interested in understanding why exactly one would use these ...
Tristan Maxson's user avatar
11 votes
0 answers
141 views

How to solve general wave equation and dispersion relation using Fourier series? [closed]

In this paper (open access), the authors used Fourier series with most general wave equation to find the dispersion relation. I am presenting some main equations as snippets to depict their solution. ...
Siddhant Singh's user avatar
14 votes
1 answer
303 views

Is basis set superposition error reduced when using the GAPW method?

CP2K implements the Gaussian and Augmented Planewaves (GAPW) approach for all-electron calculations. My understanding is that the GAPW method involves using atom-centered Gaussian type orbitals to ...
Hayden S's user avatar
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9 votes
2 answers
606 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 ...
Alfred's user avatar
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12 votes
2 answers
1k views

Are meta-GGA functionals SCAN (and its variants) ok to use in planewave DFT with the PBE pseudopotentials?

The meta-GGA SCAN functional has been there for a while. Despite the lack of SCAN (ultrasoft/PAW) pseudopotentials, various works used it in plane-wave pseudopotential calculations with ...
bzbzbz's user avatar
  • 701
14 votes
2 answers
769 views

When are atomic-orbital-basis (rather than plane-wave) methods appropriate in periodic DFT?

For example, GPAW supports both plane-wave and atomic-orbital basis methods. I know that atomic-orbital basis methods can have difficulty with electrons occupying vacancies for example, but what ...
Tristan Maxson's user avatar
23 votes
3 answers
930 views

How to do periodic DFT calculations using Quantum ESPRESSO?

I have only done quantum mechanical computations using non-periodic wavefunctions. I'd like to try to periodic-wavefunction density functional theory. Quantum ESPRESSO seems like a good package ...
Cody Aldaz's user avatar
  • 7,997