Questions tagged [density-functional-theory]
For questions about simulations using Density Functional Theory.
102
questions with no upvoted or accepted answers
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Orbital magnetization in periodic solids
The orbital magnetization in periodic solids has been nicely described by the so-called modern theory of magnetization [1,2,3,4].
$$\tag{1}
\mathcal{M}_{orb} = -\frac{1}{2} \Im \sum_{n,\mathbf{k}} f_{...
- 2,048
11
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241
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Calculating Core-Level Binding Energies (XPS) using DFT
I'm pretty new to DFT calculations but I'm trying to learn how to do X-ray photoelectron spectroscopy (XPS) calculations, particularly for open-shell molecular systems in common non-periodic DFT codes....
- 111
11
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129
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Handling multiple self-consistent solutions with DFT+U
It is well-established that within the DFT+U framework, one can achieve several self-consistent solutions with greatly varying energies for the same exact magnetic ordering. In 2010, Meredig et al. ...
- 7,281
8
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84
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How to use the HNC approximation to find the change in grand potential
I am reading Hansen and MacDonald's Theory of Simple Liquids, and I am going through Integral Equation theories.
In section 4.3, they put forward the equation (4.3.14),
$${\small \Omega _{\phi} = \...
- 4,141
7
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90
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Calculation of charge transport with the non-orthogonal basis Hamiltonian based on the non-equilibrium Green's function method
I am thinking about one question. If the Hamiltonian matrix is based on the non-orthogonal basis, how to compute the charge conductance with the Non-Equilibrium Green's Function (NEGF) method.
Suppose ...
- 193
7
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113
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How to do parity analysis of band extrema?
To check whether electronic transitions are allowed between valence band maximum (VBM) and conduction band minimum (CBM) as per Laporte's rule, the parity of VBM/CBM is needed to be known. This paper ...
- 395
7
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144
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Scaling and speed-up of real-space DFT calculations using finite elements approach
I have recently encountered this paper in which the authors have formulated Kohn-Sham equations using the finite elements package deal.II, leading to an open-source software called DFT-FE.
It stated ...
- 3,921
6
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58
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Variation of Conduction band minimum and valence band maximum with applied strain in semconductors
I have been using the Deformation Potential theory to evaluate the electron scattering rates in nanomaterials. In each case, I was under the impression that the Conduction Band Minimum (CBM) and the ...
- 2,603
6
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130
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5
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67
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Can the electron charge density of two material systems be similar?
Broadly given two electron charge density (ECD) fields, is it possible to distinguish between the elements present in both the systems?
Since the ECD does not explicitly present any information on the ...
- 1,481
5
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38
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How to calculate anisotropic exchange J $J_{xy}, J_{xz}, J_{yz}, J_{yx}, ...$ using 4-state mapping and DFT?
In this review, the authors present several schemes to calculate various quantities like single-ion anisotropy, DMI, and anisotropic exchange J using DFT. For instance, the DMI term in the y-direction ...
- 2,281
5
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62
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VESTA using command line
Can anyone please show me how to make a supercell with VESTA
using a single command line without opening a GUI.
- 161
5
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107
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SCF calculations for new materials with unknown properties (e.g. charge, spin, magnetization) using Quantum Espresso
Performing SCF calculations for crystal structures using Quantum Espresso sometimes gives me this error.
...
5
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68
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d-d transitions in materials with transition metals in DFT
While reading the literature on the absorption spectra of materials from the MPX3 group (M= Mn,Ni,Co, Fe; layered antiferromagnets) I come across expressions such as d-d transitions, which are visible ...
- 601
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141
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Actual calculation of Coulomb energy in DFT softwares
I have a question about the actual calculation of classical Coulomb interaction term in density functional theory (DFT) softwares.
Of course I understand the form Coulomb energy as:
$\int\int \frac{\...
- 1,779
5
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42
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Benchmarking DFT vs Experimental Gaps - Confusion over Fundamental and Optical Gaps
Recently, I've come across discussions about the differences between fundamental (or electronic) bandgaps and optical bandgaps, with the two quantities differing mainly by the electron-hole binding ...
- 1,034
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114
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How to calculate the number of interstital electrons from Quantum Espresso charge density outputs?
I have calculated the charge densities (in 1D, 2D and 3D formats) with the help of Quantum Espresso DFT.
The system (/material) is simple, two atoms in an unit cell.
However, I want to determine the ...
- 859
5
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83
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How to find the most stable facet for a crystal?
I am trying to find the most stable facet for a crystal, but since there are many possible choices, like (1 0 0),(1 1 0),(1 1 1),(2 1 0), etc. My questions is:
I am wondering how should I determine ...
- 1,977
5
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78
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Does a TD-DFT excitation from a closed-shell determinant only include the alpha electron part?
From an input in ORCA 5.0.3
! PBE 6-31G*
%TDDFT NROOTS
3
END
* xyz 0 1
H 0. 0. 0.
H 0. 0. 0.7414
*
the output includes
...
- 51
4
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53
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DFT+U: localizing electrons on combination of atomic orbitals
TLDR: DFT+U is a cheap scheme to help localize electrons on atomic orbitals by penalizing fractional occupancies of such orbitals. However, when one tries to localize an electron/hole on an atomic ...
- 809
4
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33
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supercell nscf kpoints for optical properties
I am calculating the optical properties of 200 atoms supercell with quantum espresso. What is the approximate number of the nscf kpoints (nk nk nk)should I start with, to avoid lengthy kpoints ...
- 161
4
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47
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How to Install GIPAW on Ubuntu with QE installation from Ubuntu Repositories
I've just installed Quantum Espresso on Ubuntu using the command:
sudo apt install quantum-espresso
everything went well and I can run calculations on QE normally. ...
- 61
4
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47
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How to calculate the distortion of molecule?
I have a set of molecules that are generated from a regular cyclohexane and have varying amounts of substitutions and double bonds. I need to compute the amount of distortion that each of these ...
- 2,742
4
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122
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Quantum ESPRESSO "Error in routine do_projwfc (5010): reading projwfc namelist"
I'm running a PDOS calculation in QE but the file has an output and has an error.
Input:
...
- 301
4
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0
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138
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Interpretation of total energy in SCF calculation using Quantum Espresso
I am performing SCF calculations using Quantum Espresso for crystalline materials to determine the band gaps and energies. A sample output for one of the crystals is shown below.
...
4
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0
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55
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How can I improve the visualization of a band structure plot for a dense supercell?
I computed the band structure of my material's supercell using Quantum ESPRESSO,but the resulting plot appears to be densely populated with bands, like in the picture bellow:
Could someone provide ...
- 1,957
4
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81
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Why my scf calculation with 30*30*30 k-points grid is stuck in the same line for more than 6 hours?
I'm running a scf Quantum ESPRESSO calculation on a cluster to get the optical properties of my material. I noticed that the output file is stuck in the same line for more than 6 hours even though ...
- 1,957
4
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0
answers
48
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Compare FCC structure's DFT band result with ARPES data
FCC structure's crystal primitive cell is not cubic.
However, when we use ARPES to measure a FCC crystal, we usually choose a cubic Brillouin zone, and the experiment's path is not the FCC primitive ...
- 41
4
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144
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Which researchers in electrical engineering do work related to DFT?
I would like to gain knowledge about how DFT calculations can be specifically used in the subject of electrical engineering. It would really help if people in the community can direct me towards ...
- 1,117
4
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44
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Modified Poisson-Boltzmann confusion about chemical potential and electrostatic potential
Within the Poisson-Boltzmann formalism the boundary conditions are often chosen such as $\phi^{S}$, the electrostatic potential in bulk solution far away from the interface (Galvani potential) is ...
- 1,222
4
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52
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q-points weighting factor in QE
When using Quantum Espresso to perform phonon calculations, one can specify a grid of q-point using ldisp=.true. (Monkhorst-Pack grid)
If I ask for a AxBxC grid, the code will reduce this grid taking ...
- 1,222
4
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answers
39
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Predicting the band gap or some other properties of materials before running any calculations
Can we some how predict what sort of modulation will doping do to a material without actually running any calculations. Like perhaps we use the already known DOS of Zn in order to predict whether the ...
- 1,641
4
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87
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Why can't DFT calculate the energy of magnetic diatomic molecules accurately?
I am trying to calculate the reaction enthalpy change of $\ce{2H2 + O2->2H2O}$, my plan is to calculate the energy of $\ce{H2, O2 \text{and} H2O}$, respectively, then do the simple math.
But I find ...
- 1,977
3
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27
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Constrained geometry optmization: Molecule interacts with its surroundings
I have a water cluster(suppose) generated from MD run. Now, I want to optimize the geometry of only one water molecule of interest using QC methods (e.g. B3LYP/6-31+G(d,p)). I intend that the water ...
- 810
3
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24
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How to perform atomistic spin dynamics (ASD) Ab Initio Molecular Dynamics (AIMD) using VASP?
I have tried normal AIMD simulation using VASP for Non magnetic materials. Now, I am interested to perform the molecular dynamics simulations for the finite temperature for Magnetic materials to ...
- 31
3
votes
1
answer
46
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How to read UPF pseudopotential for ultrasoft pseudopotential simple in a fortran program
I'm currently working on calculating semiempirical local and nonlocal matrix elements for Ga. To proceed with my calculations, I need to extract specific parameters from the UPF (Unified ...
- 371
3
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0
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25
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Discrepancy between Force Convergence in Geometrical Optimization and SCF Calculation in VASP: Reasons and Troubleshooting Suggestions
During a geometrical optimization of ions and lattice parameters in VASP, the forces acting on atoms were minimized to less than 0.01 eV/Å. However, when performing the subsequent self-consistent ...
- 849
3
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28
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How do I calculate XPS spectra for molecules to match experimental spectra?
I am trying to calculate the XPS spectra using the ICORELEVEL method in VASP, both using initial and final state approaches, for C1s and F1s electrons. My systems are single molecules.
However, my ...
3
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0
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44
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My INCAR file, POSCAR, and KPOINTS are same for GGA, however after the PBE calculation, I found that the bandgap is Changing. Why is that happened?
INCAR, POSCAR, and KPOINTS are the same but for the same calculation, the bandgap is changing.
First, I relaxed the structure then did the self-consistent calculation, and bandstructure calculation. ...
- 31
3
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0
answers
19
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How to calculate kslice_b2 and kslice_b1 in wannierization?
How is reduced coordinates calculated in wannier90? examples 17- 18 , 29
- 31
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Are then any material property solvers (from Charge Density) available in python?
I am looking to predict properties like the Bulk Modulus, total energy, etc., all from the charge density I have as input (CHGCAR file)
- 1,481
3
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25
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Convex hull calculations with WIEN2k
How does one do the calculation of a convex hull with the WIEN2k code for the formation energy of alloys?
- 31
3
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51
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Which is better? Rashba effect or Dresselhaus effect?
My current research focus is on the band splitting observed in 2D perovskite. Existing literature suggests that site inversion asymmetry (SIA) may lead to the Rashba effect, while bulk inversion ...
- 405
3
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24
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Kslice in brillioun zone
Can anyone help me about the same issue. How to find reduced coordinate of reciprocal lattice vector which defines kslice in brillioun zone?
- 31
3
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23
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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 - ...
- 31
3
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52
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Are the Lagrange multipliers used in Kohn-Sham DFT/HF-based quantum molecular dynamics real valued?
I have seen it written in several places that the matrix of Lagrange multipliers used to impose orthonormality in quantum molecular dynamics schemes based on Kohn-Sham DFT or Hartree-Fock for instance,...
- 141
3
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0
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140
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Noncollinear band structure calculation with VASP
I am trying to do a band structure calculation of a noncollinear magnetic system. I am getting results that are nowhere close to what I'm expecting. I need help checking if I am following the right ...
3
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142
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Electronic Structure Calculation with External Field
There are various programs for calculating energy states for molecules (ORCA, Gaussian, ...). Is there also software that allows the same simulations with an additional external potential (e.g. ...
- 31
3
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144
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Help with Mathematica for optimizing a Gaussian basis set for a hydrogen atom in a magnetic field
This is a follow-up to my previous question: Optimal Gaussian basis set for hydrogen atom in magnetic field
Brief description of the problem
I would like to find the ground and excited states of the ...
- 233
3
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0
answers
65
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The electrode down-folding region is 0 in the device region
When I run transiesta calculation, the scf converges, and the tbtrans output shows the following error,
...
- 359