39
votes
Accepted
Is there any DFT code or software that has the option to use this exact exchange-correlation energy functional?
Below is a summary of what I have found:
What is meant by "Exact exchange"$\,$?
The question mentions the following (in order of how they were presented in the question):
Exact exchange-correlation ...
15
votes
Why does orbital-free DFT scale linearly with system size?
There is linear scaling DFT, where you use density matrix as your object throughout SCF iterations instead of the wavefunctions. The linear scaling comes from the sparsity assumption/truncation on the ...
- 1,086
13
votes
Difficult cases for converging Kohn-Sham SCF calculations
A few materials/simulation boxes I've had some proper trouble with:
HSE06 + noncollinear magnetism + antiferromagnetism, Vasp noncollinear:
This was a strongly antiferro material (4 Fe atoms, in an ...
- 1,436
12
votes
Accepted
When are atomic-orbital-basis (rather than plane-wave) methods appropriate in periodic DFT?
The clearest example in my mind is if you want to understand the orbital-based contributions to some phenomena (e.g. bonding, a reaction energy), particularly if the periodic material being modeled is ...
- 7,451
12
votes
What is the status of graphics processing units in plane-wave DFT?
I can't say much about the popularity of GPUs in practical calculations.
From a development point of view the speedups that can be expected from GPUs in plane-wave DFT are only moderate, probably ...
- 2,414
11
votes
Is there any DFT code or software that has the option to use this exact exchange-correlation energy functional?
Whenever you see EXX, a warning flag should go up inside your head. It is never clear whether one means just using Hartree-Fock exchange in a DFT calculation, implying a generalized Kohn-Sham scheme ...
- 20.1k
11
votes
Accepted
Why does orbital-free DFT scale linearly with system size?
In orbital-free DFT, the key quantity is the particle density (not the density matrix, the actual density). The particle density is a scalar 3D field; when we increase the particle number in our ...
- 8,567
10
votes
Difficult cases for converging Kohn-Sham SCF calculations
This will be a long answer, so I will divide it in parts.
Woods paper
A significant limitation of the Woods et al paper is that it excludes atomic-basis set calculations where convergence ...
- 20.1k
10
votes
What is the status of graphics processing units in plane-wave DFT?
While I can't comment on concrete speed-ups as I'm not very familiar with GPU programming itself, I would like to point out that most of the computing time is spent in FFT and GEMM (matrix matrix ...
- 928
9
votes
What is the status of graphics processing units in plane-wave DFT?
I experienced[1] about 5-10 times speedup with GPU accelerated Quantum Espresso on Tesla V100 32 Gb compared with Intel Core i7 9700K processor with 8 cores and 32 Gb RAM. The above mentioned system's ...
- 730
8
votes
Accepted
Can GW-BSE quasiparticle calculations only be run on norm-conserving pseudopotentials (NCPPs)? If so, why not?
The GPAW code can do GW/BSE and it uses purely PAW potentials. So it's absolutely possible to do GW/BSE with PAW sets. The involvement for the implementation, however, is another topic. From Kevin J. ...
- 1,436
7
votes
problem using GPAW in Google Colab
I hope it's okay to "self-answer". So I also posted this question in the GPAW mailing list and one of the users in the mailing list who go by the handle mazay0 offered a different means of ...
7
votes
Copper FCC structure using ASE (Atomic Simulation Environment) library in python
First, I want to show a general way of checking the minimum bond length of a structure in ASE. Using your structure as an example, you can get the distance matrix in ASE by ...
- 1,970
6
votes
Accepted
What is the number of bands in GPAW?
The number of bands you set is usually the total number of bands, i.e. the number of valence bands plus the number of conduction bands. For the calculation of the ground state density, you need a ...
- 8,567
6
votes
Why does orbital-free DFT scale linearly with system size?
For linear scaling both Hamiltonian matrix ($H$) and density matrix ($D$) need to be sparse. If either $D$ or $H$ are dense, then the resulting scaling is quadratic $O(N^2)$. When both $H$ and $D$ are ...
6
votes
Difficult cases for converging Kohn-Sham SCF calculations
It is well-established that it can be quite difficult to converge the SCF for certain (hybrid) meta-GGA functionals compared to their (hybrid) GGA counterparts. This is especially true for plane-wave ...
- 7,451
5
votes
Difficult cases for converging Kohn-Sham SCF calculations
Here's some calculations I had some problems with:
LaFeO$_3$ on LaAlO$_3$ with an adsorbed O atom. $\sqrt{2}\times\sqrt{2}$ perovskite cell in the x-y direction. 5 layers of LaAlO$_3$ (alternating ...
- 3,191
5
votes
Accepted
What is the status of graphics processing units in plane-wave DFT?
I recently installed VASP GPU version provided by NVIDIA (here's the installation tutorial) on my machine that has an RTX 2080 Ti GPU. GPU version was announced for ...
- 2,022
5
votes
When are atomic-orbital-basis (rather than plane-wave) methods appropriate in periodic DFT?
The question is related essentially to solve the Kohn-Sham equation with an atomic-like basis set. In fact, different implementations of DFT are distinguished mainly by their basis set and how they ...
- 15.4k
5
votes
Why does increasing the cell size affect the energy of molecules?
The issue was that I used too large of a grid spacing at 0.26 Å. This value I got from a utility tool from GPAW, cutoff2gridspacing. From an old convergence test with VASP on similar systems the ...
- 183
5
votes
Accepted
Is it possible to do a vc-relax calculation using GPAW?
This is more of an ASE question, given that a python script using ASE is employed to set up and run the GPAW calculation. GPAW only is used to compute energies/forces/stresses for a given structure, ...
- 1,526
4
votes
Accepted
What is just "LDA" in GPAW?
According to GPAW's documentation, GPAW would use its own LDA implementation, but if I interpret the table correctly, that should correspond to libxc's LDA_X + LDA_C_PW:
Exchange-Correlation ...
- 4,891
4
votes
Accepted
Placing an atom along the line of the dipole moment of another molecule in ASE/GPAW
It seems to me you simply want to place some molecule/atom at some fixed distance from the closest atom along a given direction?
If the above is correctly understood I would do this instead:
...
- 4,394
3
votes
The projector augmented wave (PAW) method, pseudopotentials (PP), and exchange correlation functionals
PAW is proposed to deal with the interaction between electrons and ions. However, PBE or GGA (PBE just one kind of GGA) is just the exchange-correlation functional. You can think PAW and PBE are ...
- 15.4k
3
votes
How better is PAW available in VASP when compared to that present in PS Library?
This isn't a perfect comparison of what you asked, but I think it can help. I'll refer to PAW datasets as "pseudopotentials" here since that is how they are used in practice.
According to ...
- 3,191
2
votes
How do I find the electric field components from an FDTD simulation using GPAW?
You can get the induced field components from an induced field object. If you call your induced field object ind, then you can get the Fourier transform of the field components by accessing ind....
- 693
2
votes
ASE GPAW variable cell relaxation
After some fiddling around (with the inputs from @kristof bal) I understood that the filters dont quite work with the finite difference mode of GPAW. It works perfectly with the PAW mode (given by ...
2
votes
How to Create a 2D Structure of Boron (Brophene) using ASE?
You could define the formula for a graphene-like structure. For example, ase.build.graphene(formula='B2', a=2.46, thickness=0.0, size=(1, 1, 1), vacuum=None)
- 21
2
votes
How to Create a 2D Structure of Boron (Brophene) using ASE?
As you said, borophene has the same structure as graphene. Then you can first build a graphene structure in ASE, then change every atom to boron, and scale the lattice parameters to be that of a ...
- 1,970
1
vote
Convergence Issue using GPAW for Anatase and Rutile
In terms of cutoff energy, this is not surprising; consider that this is the number of basis functions you need to accurately describe your wavefunction/density. Increasing cutoff increases your ...
- 495
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