Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

44 questions with no upvoted or accepted answers
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17
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128 views

What are the recent developments of TDDFT to simulate the excited properties of materials?

The time-dependent density functional theory (TDDFT) and the many-body perturbation method (GW@BSE) are considered as the two most popular and successful methods to describe the excited-stated ...
12
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104 views

What are the recent developments of GW@BSE to simulate the excited properties of materials?

A twin question related to the TDDFT method is asked in another post. But any comparisons between both methods in recent developments are welcome. The time-dependent density functional theory (TDDFT) ...
12
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109 views

Orbital-free DFT and Density Functional Tight-Binding: Comparison

There are many flavors of DFT that are alternative to, or go beyond the Kohn-Sham formulation (KS-DFT). Some of these are based on approximations that sacrifice accuracy when compared to KS-DFT, but ...
11
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97 views

Is there an example in which TD-DFT was successful in describing photophysical or photochemical processes?

Time-dependent Density Functional Theory has been around for quite a while now, seeing Density-Functional Theory for Time-Dependent Systems, and so it has been developed extensively, implemented in ...
11
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161 views

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_{...
11
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132 views

Inconsistent data of chemical potential from different papers

I am looking for chemical potential from literature.$^{1,2}$ I compared the method and data they provided. They use the Fitted Elemental Reference Energy method via GGA+U on VASP employing PAW. The U ...
10
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79 views

Single electron transfer periodic DFT in VASP

I have the following question: I am currently studying the electrocatalytic $\ce{CO2}$ reduction reaction (CO2RR) on $\ce{Cu}$ materials using periodic DFT calculations and I am using the ...
9
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65 views

Crystallography: How to sample *unique* structures from configuration space? (binary alloy supercell)

I'm working with a binary alloy system (call it 'AB'), and I'd like to generate a few unique configurations for DFT purposes. My primitive cubic unit cell consists of 4 atoms; i.e. 4 positions. Thus, ...
9
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133 views

How to do a Sampling on the boundary of Brillouin zone in VASP

I use VASP to do my DFT calculation. I have to do a self consistent calculation to generate my CHGCAR. I want to ask is there anyway to write the KPOINTS file to generate K-meshing grid which can ...
9
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48 views

Is it possible to construct a tight binding matrix of high atomic layer thin film from the lower one?

Given a tight binding matrix of a thin film system with a few atomic layers, is it possible to construct a tight binding matrix of higher atomic layers thin film from the lower one? For example, I ...
9
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109 views

How to interpret WannierTools Python code that generates tight-binding model in the wannier90_hr.dat format?

I am getting myself acquainted with Wannier Tools. Wannier Tools requires two inputs, a wt.in file, and a .dat file. This ...
8
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133 views

transition dipole matrix element

When doing DFT calculations of periodic solids, from either $\mathbf{k \cdot p}$ perturbation theory or simply using the trick $\mathbf{r} \rightarrow i\partial_{\mathbf{k}}$, one can obtain $$ \...
8
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72 views

Structural biology vs condensed matter prediction

I have two main modeling research lines: one related to structural biology (including rational drug design, de novo design, polymorphism, etc.) and the other one related to condensed matter (...
7
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57 views

Why do I get negative charge density values in the core of atoms when I perform DFT calculations with PAW?

We are all aware of the fact that negative charge densities in the atomic cores are an artefact of Density Functional theory Calculations using Projector Augmented Wave (PAW) method. But what is the ...
7
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37 views

The quantum spin Hall phase with Z2 = 0?

I used first principle calculations to study the thin film model. An obvious crossing was shown to appear at the gamma point when the edge state was calculated, which was originally predicted to be ...
7
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57 views

Software for calculating the mirror Chern number of 2D systems?

Can anyone please explain to me how can I calculate the mirror Chern number of a 2D system? I will be very thankful if you can refer me to a package or software which can directly perform mirror Chern ...
7
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110 views

How to fix gauge in Quantum ESPRESSO?

I am trying to use Quantum ESPRESSO to manually calculate the Berry phase using the Berry connection, due to evolution along a closed loop in k-space. I want to do this manually instead of using ...
7
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135 views

The gap was open when I was doing an HSE + SOC DFT calculation

I used VASP as my DFT software to do a calculation on an anti-perovskite crystal. I try to reproduce the band structure from literature which was calculated based on HSE + SOC calculation. Their ...
6
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85 views

Physical interpretation of k-points

What is the Physical interpretation of the k-points used in ab initio calculations? Why must the number of k-points be optimized rather than just using some large fixed number of them?
6
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20 views

TIP5P model for water in RISM

I want to use the implementation of ESM-RISM from the Otani laboratory using Quantum Espresso. For my system I ask for $H_2O \; (H^+Cl^- \; 1M \; aq.)$, following the literature the best way to ...
6
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68 views

Why am I getting DOS like this in Quantum ESPRESSO?

I am working on $\ce{GeHfTe}$ and in the case of a non-collinear calculation, I am getting the DOS in the attached photo. I have already relaxed my structure with VC-relax and it is converged with ...
6
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76 views

Calculate FF interaction energy of small molecular dimers

I have a set of molecular dimers (~25 atoms) for which DFT-D3 interaction energies are calculated by Psi4 and Turbomole program. Now I want to compare these values against Force-Field methods like UFF/...
6
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69 views

Two-stage unbinding & binding energies with DFT

I'm trying to calculate the stability of the product of a coordinate bonding process of molecules A and B in the polarizable continuum solvent model (PCM, solvent set to water). I'm getting energies ...
6
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139 views

In VASP, which option is better for monolayer relaxation: ISIF=3 or ISIF=4?

Since I have started working on monolayers I was using the ISIF=3 tag for relaxation, this was after recompiling VASP with the modified "...
6
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52 views

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. ...
6
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27 views

Is it possible to calculate the variation of magnetization M(T) for a diluted magnetic semiconductor?

Is there any simulation program (for example a DFT package) to determine the variation of magnetization M(T) for dilute magnetic semiconductors or doped semiconductors with different concentrations of ...
6
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56 views

Is it necessary to terminate the surface ions in a quantum dot?

I was trying to study quantum dots of ZnO. But I'm pretty new to creating and passivating 0-dimensional particles. Is it always necessary to passivate the free surface of the quantum dot? Regarding ...
6
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179 views

Is there any way to simulate the Polarization vs Electric Field loop of BaTiO3 using Quantum ESPRESSO?

I'm new to the Quantum ESPRESSO package. There are articles outlining the procedure of indirectly simulating the P-E loop of piezo-electric materials via Berry phase calculations.One procedure is ...
5
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50 views

How to identify/treat delocalized pi bonds in DFT

For a structure such benzene, the pi bonds between the carbon atoms are said to be de-localized. Therefore the electrons are expected to be exchanged in between individual C-C bonds. When dealing with ...
5
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33 views

Cutoff length for vdW correction in DFT calculation

In classical MD simulations of lattice structures, whenever we are trying to incorporate vdW corrections to the atomic force calculation, we need to set up cutoff length beyond which the vdW ...
5
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26 views

Case study: KPOINT and band parallelization in Quantum ESPRESSO

I am testing Quantum ESPRESSO with different values for Npool and bands in order to calculate run time. ...
5
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0answers
40 views

Comments on the electronic relaxation time variation between nanowire configurations

I am studying Si nanowires with different cross sections. In my work, I plan to evaluate the thermoelectric performance variation between different configurations. To achieve this, my current approach ...
5
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36 views

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), $$\Omega _{\phi} = \Omega _0 + \...
5
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40 views

Reaction rate estimation for relatively complex reactions

I am looking for a summary of your favorite methods to estimate a reaction rate constant for a “complex” polyatomic reaction (requiring a cell of ~100 atoms) from ab initio methods (the one I have in ...
5
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48 views

Nanowire Band Structure using Siesta DFT

I'm working with the Siesta DFT software, and managed to reproduce the band structure of bulk Si without any issues. However, when trying the same with a Si nanowire, the band structure looks nowhere ...
5
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106 views

What is the relation between enthalpy, ionization potential, internal energy and HOMO/LUMO?

Is there any relation between enthalpy, ionization potential, internal energy and HOMO/LUMO? I am dehydrogenating a molecule and I need to study the enthalpy of dehydrogenation. If I get any relation ...
4
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22 views

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 ...
4
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31 views

What are the challenges in using DFT to study the Hydrogen Evolution Reaction of (111), (110), (100) and (011) planes of Cobalt (III) Phosphide (CoP)

What are the challenges in using DFT (implemented in the VASP code) to study the hydrogen evolution reaction (HER) of the (111), (110), (100) and (011) surface planes of Cobalt (III) Phosphide CoP
4
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36 views

Smearing values for different codes

I am using Quantum Espresso along with a different code, I am performing calculations on Platinum bulk. After choosing the "cold" smearing (which I read is a good choice for metals) with a ...
4
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0answers
37 views

What computational steps needed to characterize the Weyl points?

I am trying to learn the characterization of Weyl nodes computationally. For this, I am using Wannier90 and Z2pack codes in interface with Quantum ESPRESSO. I have done scf, nscf, bands structure, DOS,...
4
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0answers
33 views

How to define ferrimagnetism in quantum Espresso

I would like to pick this problem from my previous post See link. I am clear about how to define antiferromagnetism in QE. Here I am with another issue. I am ...
3
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0answers
48 views

Job stops in between without showing any error

I am trying to calculate the dos of one bulk system. My dos calculation job stops in between without showing any error. Here I am attaching the link of my input dos calculation files. CONTCAR file is ...
3
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22 views

DOS projection in alternate axis for eg and t2g contributions

I am studying doping in 0D and 2D perovskites which present tilted octahedra. It is important for me to analyze the contributions in the PDOS in terms of $e_g$ and $t_{2g}$ levels for d orbital in the ...
3
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20 views

How to get energy eigenstates using plane wave basis wavefunction .hdf5 output from Quantum ESPRESSO?

When compiled with the HDF5 flag on, Quantum ESPRESSO (QE) saves wavefunctions in the .save folder. At each k-point, we have an $m\times n$ matrix, where $m$ are the complex number entries of ...