Questions tagged [pseudopotentials]
Refers to the approximation of core electrons by effective potentials. Used in plane-wave and Gaussian based theories.
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Citing a pseudopotential
I conduct my DFT calculations using the SIESTA DFT package. For this, I obtained the pseudopotentials from this site which says that they have obtained the data from the Abinit database. However I do ...
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Which specific perturbation do we consider applying to the potential when defining the energy derivative of the log derivative?
Norm-conserving pseudopotentials are defined such that the energy derivative of the log derivative of the real and pseudo wavefunctions agree at $r>r_c$. I understand that although valence ...
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How to understand the energy derivative of the logarithmic derivative of a wavefunction when deriving norm-conserving pseudopotentials
The 4th desirable property of a norm-conserving pseudopotential given by Hamann et al is for the 'logarithmic derivatives of the real and pseudo wave function and their first energy derivatives agree ...
6
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1answer
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Quantum Espresso energy cutoff for different pseudopotential
I've been told that I should use the potentials from the Standard Solid-State Pseudopotential (SSSP) library in my simulations. I am interested in $\ce{Pt}$, $\ce{O}$, and $\ce{H}$. Oxygen is ...
10
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1answer
113 views
Error in nscf calculation while considering Spin Orbit Coupling in Quantum ESPRESSO
I am trying to do the band structure calculation considering the Spin Orbit Coupling but getting the following error:
...
8
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1answer
106 views
VASP GW PAW Pseudopotentials
What is the difference between the GW and non-GW potentials in VASP. While it is clear that the GW potentials should be used with GW calculations, the documentation also states that these potentials ...
10
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1answer
160 views
Recommendations to treat 4f electrons (valence) of Yb3+ in magnetic systems in VASP
I need help with: I would like to know what is the most common approach to treat valence 4f electrons of lanthanides (3+ charge) in VASP that circumvents the calculation problems shown below. (or more ...
5
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1answer
41 views
What does the "pn" column mean in this pseudopotential file?
In this SSSP pseudopotential file for Quantum ESPRESSO, what does the "pn" column mean?
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What is a Padé approximant?
I have been looking at using Goedecker-Teter-Hutter (GTH) pseudo-potentials and I came across the abbreviation PADE.
I was wondering what this abbreviation actually stood for and how it is related to ...
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1answer
54 views
Convert PSP8 pseudopotential files to UPF format
Is there a way to convert psp8 pseudopotential files (used for abinit) to UPF format (used for Quantum ESPRESSO)? I noticed there is the upfconv.x utility in ...
15
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1answer
168 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 ...
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What are some of the advantages and disadvantages when using shape consistent pseudopotentials as compared to energy consistent pseduopotentials
From the literature as well as the answer to the question What is the meaning of energy-consistent and shape-consistent in the context of pseudopotentials? I can see that the key difference between ...
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1answer
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Why are Norm-conserving Pseudopotentials considered so important?
So I am aware that a norm-conserving pseudopotential enforces the conditions that:
Inside the cut-off radius, the norm of each pseudo-wavefunction is identical to its corresponding all-electron ...
6
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1answer
105 views
What is the meaning of energy-consistent and shape-consistent in the context of pseudopotentials?
I am trying to use pseudopotentials to model scattering from heavy molecules.
However, I am confused by some of the terminologies of pseudopotentials/ECPs:
Norm-conserving according to Wikipedia and ...
7
votes
3answers
454 views
For which elements should I include spin orbit coupling in Quantum ESPRESSO?
I'm trying to study a Yb-Ge-Sb compound and would like to include spin-orbit coupling (SOC). In Quantum ESPRESSO, this is done by including the following tags in the ...
14
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1answer
104 views
Analytical expression for an atomic lattice "muffin-tin" potential for purposes of illustration and simple scattering calculations
Before taking the deep dive (see linked questions below) into calculating the diffraction of 20 to 200 eV electrons from crystal surfaces, I'd like to generate a simple "muffin-tin potential"...
6
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1answer
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How better is PAW available in VASP when compared to that present in PS Library?
Papers with DFT calculations that use VASP work with PAW pseudopotentials which are also available in PS Library. I assume they are different since VASP is commercial. Given that, how different are ...
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1answer
270 views
The projector augmented wave (PAW) method, pseudopotentials (PP), and exchange correlation functionals
Disclaimer: Assume the questioner is a novice in DFT
Is PAW an improvement over the pseudopotential method? In terms of Perdew, Burke, and Ernzerhof (PBE) parameterization, what is the difference ...
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461 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 ...
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127 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 ...
13
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2answers
365 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 ...
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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 ...
6
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1answer
57 views
Are there properties that can only be calculated with a given set-up?
If you do a bibliography search about the codes used in matter modeling, you will find a large list.
I played with a few of them (both free and commercial) and one of my findings is that the ...
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2answers
324 views
What are the types of pseudopotentials?
I would like to know what are the different types of pseudopotentials, the pro and cons, and what properties can/cannot be calculated with them?
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How do I generate an aluminum force-field for a LAMMPS input file? [closed]
I have been assigned a project on the generation of a force-field of Al (aluminum) for a LAMMPS potential.
I have no idea how to proceed and what to do next. Can anyone please let me know how should I ...
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2answers
371 views
How to convert Unified Pseudopotential Format (UPF) into Ultrasoft Pseudopotential (USPP) format?
I am working on DFT code having plane wave along xy axis and bspline in z direction. For calculating the properties of TMD materials, spin orbit coupling must be included but i did not find fully ...
11
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1answer
63 views
How to generate relativistic pseudo-potential using Vanderbilt USPP that captures spin-orbit coupling?
I have used Vanderbilt USPP for generating a pseudopotential that does not include the spin-orbit term.
But I want to have the spin-orbit coupling term included in the pseudopotential, to do ...
15
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1answer
211 views
Can GW-BSE quasiparticle calculations only be run on norm-conserving pseudopotentials (NCPPs)? If so, why not?
I've read in some texts that GW-BSE quasiparticle calculations have only been implemented on Norm-conserving Pseudopotentials (and not Ultra-soft or PAW PPs). Is there a conceptual reason for this? I ...
15
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1answer
187 views
VASP Dielectric constants: What potential to use?
I've simulated the dielectric constants using the LEPSILON = .TRUE. tag and the PBE GPAW potentials. A collegue mentioned that for accurate results norm conserving pseudo-potentials are the way to go. ...
17
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1answer
527 views
Understanding the GTH Pseudopotential
I'm new to DFT. I want to make use of the GTH pseudopotential.
I am trying to understand how this potential works. I read the article "Separable dual-space Gaussian pseudopotentials" by S. Goedecker, ...
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2answers
232 views
Norm-Conserving or Ultrasoft, which pseudopotential to choose?
Ultrasoft pseudopotential (USPP), in general, requires a lower energy-cutoff to the plane waves when compared to Norm-Conserving ones (NC). On the other hand (at least with Quantum ESPRESSO) the ...
8
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1answer
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How to generate a pseudopotential for a cation/anion?
Many DFT codes use pseudopotentials to represent the electron-ion interaction (as do most plane-wave codes and in contrast to so-called "all-electron" programs).
There are several resources on the ...
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1answer
149 views
When do relativistic effects need to be explicitly included?
For many applications with heavy metals, pseudopotentials can be used to include some amount of relativistic effects. But for what sort of systems does it become necessary to actually use a ...
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3answers
314 views
When should I include semi-core electrons in DFT calculations?
Many DFT codes use pseudopotentials (for the core electrons) and basis set functions (for the valence electrons) in order to solve the Schrodinger equation. This because simulates each electron ...