Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

Filter by
Sorted by
Tagged with
6
votes
1answer
95 views

Lattice Thermal conductivity calculation error

I have been trying to calculate Lattice Thermal Conductivity on my system using QuantumEspresso. I used phonopy and phono3py. I was successful to run these codes on Si system for practice. Now when I ...
4
votes
1answer
44 views

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 ...
4
votes
0answers
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 ...
5
votes
0answers
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 ...
6
votes
0answers
81 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?
9
votes
0answers
108 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 ...
6
votes
1answer
111 views

How does electronic iteration work in a VASP relaxation calculation?

I am a beginner using VASP to do material modeling, and I'm confused about the following questions: How does the electronic iteration work in VASP relaxation calculation? Is the electronic iteration ...
6
votes
2answers
80 views

Relation between lattice parameter and energy for relaxations

We have been wanting to do relaxation of lattice parameters as a function of the energy. I want to know the mathematical expression for this, and also the theoretical background related to this method....
8
votes
1answer
264 views

Study of supercell after creating vacuum

For studying a bulk supercell, after creating some vacuum in it, I'm confused about how to relax it. With VASP, I can do relaxation using NSW = 0 and ...
8
votes
1answer
76 views

what do I need to change about typical VASP input file to calculate the energy of a single atom?

I'm a little confused how to make a VASP input file to calculate the energy for the isolated atom: Do I need to change the lattice parameter of my unit cell or can keep the value for the whole system?...
6
votes
0answers
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 ...
9
votes
1answer
65 views

How to confirm whether a system is mott-insulator or not from DFT calculations?

I am using Quantum-Espresso and I need to study mott-insulator. Being a beginner, I am not sure, how do I confirm whether my system is a mott-insulator or not?
5
votes
0answers
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 ...
9
votes
1answer
56 views

How to identify localized surface states in the band structure

After calculating the band diagram of a structure, is there a way to identify localized surface states? I am working with Si nanowires with different cross sections. I want to determine the band gap ...
5
votes
2answers
63 views

SIESTA output wavefunctions: all vs selected?

Using SIESTA, I want to plot the wavefunctions around the Fermi level (similar to HOMO/LUMO). Also, I want to do COOP analysis. From the SIESTA manual, I can setup to write the wavefunctions ...
12
votes
0answers
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 ...
5
votes
1answer
31 views

How to fix local magnetic moment of each ions in VASP?

In spin-polarized calculation,total magnetic moment can be fixed to a specific value using NUPDOWN tag. In non-colinear spin calculation, tag ...
4
votes
0answers
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
6
votes
1answer
91 views

How to evaluate the electron relaxation time of nanostructures computationally

I am working with Si nanowires using the SIESTA ab initio code and the BoltzTraP2 Boltzmann transport equation solver. However, the output of the BoltzTraP2 code comes per relaxation time (...
4
votes
1answer
62 views

How can I build an MoS2 nanoribbon?

Are there any codes available? What is the easiest way?
6
votes
0answers
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
votes
0answers
101 views

Equations related to the first-order derivative of the wavefunction [closed]

I have two brakets (the angular momentum matrix elements) that are $$ \langle \partial_\mathbf{k} \psi_{n \mathbf{k}} | \times \mathbf{p} | \psi_{m \mathbf{k}} \rangle \tag{1} $$ $$ \langle \psi_{n \...
5
votes
0answers
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. ...
8
votes
1answer
113 views

Geometry optimization using DFT

I have been attempting to optimize the structure of a Si nanowire using SIESTA. The original structure fed into the optimization is as follows. Once it is optimized, the structure would change to ...
10
votes
1answer
158 views

Using "soft" constraints / bias in geometry optimization?

I study molecules weakly bound to nanoclusters and surfaces. During geometry optimization, I often run into problems like for example a small metal cluster behave nicely and has a given, stable ...
8
votes
1answer
443 views

Kramer's Degeneracy and Antiferromagnetism

How can one understand the concept of Kramer's Degeneracy for an antiferromagnetic system where spin-up and spin-down bands overlap due to net zero magnetic moment?
5
votes
1answer
48 views

How do I relax only the in-plane component of the unit cell?

I know that &CONTROL='vc-relax' option calculation performs a unit cell relaxation, and that the ATOMIC_POSITIONS can be ...
15
votes
5answers
442 views

What are some open-source all-electron DFT alternatives to Wien2K?

Since the beginning of the century, Wien2K has proven to be a very powerful player in computational condensed matter and materials physics. Wien2K is an all-electron periodic DFT code based on the ...
7
votes
1answer
85 views

Different band gap observed in unitcell and in the supercell

I calculated the bandgap for one system in the unit cell and in the supercell of 2x2x1 and 3x1x1. Although 3x1x1 gives the same bandgap as I got from the unit cell (1.79 eV) but 2x2x1 is giving 1.75 ...
9
votes
1answer
165 views

What is the source of error in this mBJ-LDA calculation?

I am trying to do MBJLDA calculation for bandstructure for WS2 monolayer unit cell using VASP and following the method provided here : Band Structure mBJ-LDA using Vasp, but I am getting an error ...
3
votes
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 ...
5
votes
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 ...
8
votes
2answers
107 views

Can the NCI (noncovalent interaction) index be generated starting with psi4?

Can NCI[1] index plots be generated starting from psi4? I'd be happy to just generate the NCI index values and mesh the isosurface myself. With a long-term goal to visualise various medicinal-...
10
votes
0answers
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
votes
0answers
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 ...
7
votes
0answers
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
votes
0answers
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 ...
11
votes
0answers
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 ...
9
votes
1answer
84 views

Calculating lattice thermal conductivity using Quantum ESPRESSO and phonopy

How should I calculate lattice thermal conductivity in Quantum ESPRESSO? I have installed phonopy. My Linux distribution is Ubuntu.
6
votes
1answer
56 views

Interpreting Critic2 charge analysis in metallic systems

I'm using Critic2 software to perform post-processing of the charge density of metallic alloys. With the charge density obtained from the Self-Consistent-Field calculation (for that I'm using Quantum ...
8
votes
0answers
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 (...
10
votes
2answers
83 views

Doubt about K point selection for 2x2x1 supercell

I have one doubt about K points selection for a supercell. I construct one 2X2X1 supercell with 64 atoms having a=11.19, b=11.19, c=5.59. For checking K points convergence test with energy should I ...
9
votes
0answers
72 views

How to implement a toy DFT [duplicate]

I want to learn DFT for research purposes and I need to implement a toy DFT for pedagogical reasons. I would like some recommendations regarding resources like books, articles, or any other thing that ...
18
votes
1answer
142 views

How to evaluate spin exchange parameters of a magnetic material using DFT?

I think we have to calculate total energies using different FM, AFM configurations and solve a set of linear equations. How to arrive at the set of equations for any given structure? An example from ...
6
votes
0answers
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 ...
7
votes
1answer
65 views

Eigen-values not converged, warning in Quantum espresso

I am running a simple example of vc-relax/scf for aluminum using PBE pseudo-potential.Setting are given below ...
7
votes
1answer
67 views

How to perform linear response theory calculation of U Hubbard parameter in VASP?

Following to this post, I would like to know how to perform linear response theory for calculation of U Hubbard parameter in VASP?
10
votes
2answers
191 views

Non-Convergence of the XC functional in the sense of a Taylor series

When it comes to improving the accuracy of DFT calculations, there is a well known hierarchy: starting from LDA using $E_{xc}[n]$, proceeding with GGA and its $E_{xc}[ n, \nabla n]$ dependency and ...
11
votes
0answers
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 ...
8
votes
0answers
47 views

Effect of temperature on density of states effective mass [closed]

The experimental study shows that Density of state effective mass is calculated at 300K while in theoretical study DFT yield Density of state effective mass at 0K. Why there is so much temperature ...

1
2 3 4 5
12