Questions tagged [density-functional-theory]
For questions about simulations using Density Functional Theory.
905
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Optimal Gaussian basis set for hydrogen atom in magnetic field (Part 2, help with Mathematica)
In my previous question Optimal Gaussian basis set for hydrogen atom in magnetic field (Part 1), I asked about how the authors of the article ("Hydrogen-Like Systems in Arbitrary Magnetic Fields
...
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I didn't find the results of my calculations using an HPC for Quantum ESPRESSO?
I submitted 2 jobs for the first time in a HPC to test it. it's a very light scf calculation that takes almost 5 minutes or less in my desktop. But it's been almost 1 hour that I submitted the job in ...
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51
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DFT calculation for conjugated polymers
I am new to DFT calculation.
I want to know the structure of conjugated polymers (plane angle, etc.) and their electronic and optical properties (such as HOMO-LUMO, IR, etc.).
I am using 6-311+G(d) ...
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I'm calculating the band structure with and without considering spin orbit coupling. why I need to use SOC?
I have been working on electronic properties of ternary alkali Bismuth.
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What is the best method to compute crystal structures?
I am rather new to VASP and I have seen people using different methods to compute crystal structure:
Using Birch-Murnaghan equation to find optimal lattice volume, and then adjust the structure ...
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How to perform carrier doping (hole/electron) for 2D materials by Quantum Espresso?
I tried to set the tot_charge parameter of Quantum Espresso to alter the charge of the system, but the phonon spectrum I obtained was very strange. Could anyone ...
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Question on CPU timings and/or ratio resp. DLPNO-CCSD(T) and wB97X-2-D for protein of ca. 1M Da
Suppose one has a protein of about 1 million Da, and performs a DLPNO-CCSD(T)/def2-TZVPPD/AutoAux/AutoAux calculation, and then performs a wB97X-2-D/def2-TZVPPD/AutoAux/AutoAux calculation, both via ...
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How is magnetization of a solid obtained from electron density in a DFT framework?
What's the theory behind these kind of calculation? What are keywords and concepts I have to search for?
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Geometry optimization: nuclear coordinates vs lattice parameters
I would like to know whether, at least in principle, minimization of energy with respect to nuclear coordinates leads to the same result as minimization of cell energy with respect to lattice ...
- 93
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Electronic structure of s-indacene
Structure shown in (a) is the regular $s$-indacene molecule, and (b) is a structure that i generated such that the central six-member ring remains similar to benzene. It is well-known in literature ...
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Dirac exchange energy and X_alpha LDA methods
I want to make a DFT code (by myself) that works in the RKS LDA H2 configuration. This post is a continuation of here.
Now by adding the Vosko, Wilk, Nusair correlation I have much better results :
...
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What is wrong with my results for H2? I used RKS, LDA (only exchange) and SCF (Roothaan-hall) with STO-3G [closed]
This post is a follow-up from here. The code and the plots can be found in the same folder as the script I executed here.
Now I have implemented the Becke partitionning. And I have the following ...
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Can you calculate fat ("projected") phonon dispersion bands with Quantum Espresso?
I would like to calculate the fat phonon bands for a chosen material (for simplicity, suppose GaAs), similarily as in Fig. 3 of reference [1]:
This is effectively the analogue of projected band ...
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Does it make any sense to run a TD-DFT calculation with Finite-Temperature SCF active?
I recently received the task to investigate what is happening in a fluorescent molecule in different temperatures. How the electronic population is changing and how is this affecting the electronic ...
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calculation of E-K diagram of a charge density wave ground state using DFT VASP
I have a DFT calculation in VASP are done at 0K. And CDW is a temperature dependent phenomena. Therefore for a CDW ground state calculation can I add periodic modulation in atomic position?
If so how ...
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Issues simulating the shape transition of silicon clusters using LAMMPS
I have been trying to write an input file for lammps to simulate the shape transition of a nanoparticle of silicon using multiple potentials to obtain the best structure, which I will compare with a ...
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Optimal Gaussian basis set for hydrogen atom in magnetic field (Part 1)
Copy from here https://mathematica.stackexchange.com/questions/285044/optimal-basis-set-of-gaussian-functions-for-describing-a-quantum-system
This question arose during the discussion of the previous ...
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Does loging out from the server stop my Quantum ESPRESSO calculations?
I'm doing simulation with Quantum ESPRESSO, and it's my first time to run it on a server using ssh. I ran some calculations yesterday then I logout using the command ...
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2
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Becke partitioning : Computing integrals with Lebedev and Gauss-Chebyshev quadrature
Preface:
This question is a follow up post from a previous question on MMSE: Usual way of computing exchange-correlation potential on a simple case H2 (RHF, LDA).
The radial variable substitution and ...
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Request for Transiesta - Tbtrans error: "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,
...
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Can we download DMol3 for free?
I want to try using DMol3 software for my research studies of doing optimisations and DFT calculations. Anyways I was unable to find a download link. Is it available for free? if so can anyone please ...
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Difficulty in interpreting electronic band structures in solid state physics
My background is in ab initio calculations of atoms and molecules, and I consider myself to have a good understanding of the underlying quantum theory of electronic structure and electronic spectra ...
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How the adsorption energies calculated at DFT level, is valid at finite temperatures?
The adsorption energies of atoms or molecules on any surface in a standalone DFT are inherently devoid of any temperature influence. so, let's say an atom/molecule has very weak binding, in ...
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What is the correct method to calculate ELF?
I am trying to calculate the electron localization function (ELF) using Quantum ESPRESSO.
However, I realize that it is not possible to correctly calculate it with either the Ultrasoft or the PAW ...
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Inverse Matrix Calculation
I am working on the charge transport calculation, based on the non-equilibrium green function method, for the Hamiltonian with the non-orthogonal basis. Suppose $H$ and $S$ are the Kohn-Sham ...
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Query about optical data extraction using Vaspkit
Recently I tried to extract the optical absorption data using Vaspkit (vaspkit.1.3.0/vaspkit.1.3.5]). I performed the optical calculations of one 2d system along with SOC using VASP. While extracting ...
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Usual way of computing exchange-correlation potential on a simple case H2 (RKS, LDA)
The python code is here.
I tried to do a DFT calculation for H2 Restricted Hartree-Fock with Local Density Approximation. The optimization is a scf-loop with Lagrange-multiplier only. I use the same ...
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Antibonding, non-bonding or bonding hybridization
In case of CsSnI3 and CsGeI3 perovskites, the strong antibonding hybridization of Sn-s/Ge-s state with I-p state lies near to VBM of these materials. In this informative paper (P.No.13853, 14th line), ...
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Is the pseudopotential designed for GGA also suited for meta-GGA?
VASP provides two sets of pseudopotentials(PP) for LDA and GGA respectively, but as I understand the PP is dependent on the exchange-correlation functional I use, so if I am using meta-GGA, could I ...
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Which DFT code allows 'nonuniform grids for Brillouin zone integration'?
In this Phys. Rev. B article, Chen, Salzbrenner & Monserrat provide a [n]onuniform grids for Brillouin zone integration and interpolation. According to them, they were able to accelerate the ...
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Is the Broyden's algorithm sufficient to obtain the crystal structure of a hypothetical alloy, or should something else be used?
The Broyden (Broyden—Fletcher—Goldfarb—Shanno or BFGS) algorithm can be known in the matter modeling to optimize a crystal lattice geometry — to clarify positions of nodes of a crystal lattice in ...
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could meta-GGA-r2scan descript d electron localization and polaron the same as Hybrid functional?
I notice that r2scan could be more accurate than rscan, but I am unsure if r2scan could describe the d electron localization without Hubbard+U? Or do I still need Hubbard+U with r2scan?
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Calculation of charge transport with the Non-Orthogonal basis Hamiltonian based on the Non-Equilibrium Green 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 function (NEGF) method.
Suppose ...
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Adsorption of Zn2+ on the metallic surface in VASP
I am trying to model the adsorption of charged atom (Zn2+) on the metallic surface using VASP.
Since NELECT assumes total charge (metallic surface + Zn), is it the right flag to use? Or are there any ...
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If total energies differ across different software, how do I decide which software to use?
I posted a question previously about why I got different total energy values when I ran a DFT calculation with quantum espresso compared to VASP (link to the question).
From what I understood from the ...
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PyProcar bands plot error
I am new to using PyProcar and am getting the following error when trying to plot band-structure using it:
Here is my input:
...
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1
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Start a CI calculation from HF/DFT chkfile in PySCF
I am trying to perform a CISD calculation in PySCF using the starting orbitals from an old DFT result.
The DFT result was saved on a chkfile, mf.hdf5. The code that ...
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What is the best way to compute the DFT total energy and atomic forces for given atomic positions?
I am new to DFT calculation and I want to compute DFT total energy and atomic forces of an atomic configuration, given the atomic positions and lattice vectors.
I have an extended xyz with DFT energy ...
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A cubic unit cell in DFT of volume 'V' has 'n' atoms in it, for an extended volume V' how many atoms would be there in the new volume?
We can also assume the lattice parameter of the cubic unit cell to be a and the that of the extended cell to be a', which means that V' = (a')^3
So is the number of atoms n' in the extended volume V' ...
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Eigenvalues of Hubbard occupancy matrix
I am studying Hematite (Fe2O3) Antiferromagnetic configuration using QE 7.0 (EDIT: compiled and tried 7.1) at the PBE+U level (U = 4.5).
I obtained an excellent agreement with experimental data on ...
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where to find the norm-conserving pseudopotential of rare earth metals?
I am trying to find the norm-conserving(NC) pseudopotential of rare earth metals, but all I could find are about Ultrasoft or PAW types. Is there any recommendation for NC type?
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Which component of the dielectric tensor is used in generating EELS in TDDFT?
Electron Energy Loss Spectroscopy (EELS) comes from the imaginary part of the inverse dielectric function $-\text{Im}[\varepsilon^{-1}(q, \omega)]$. If the dielectric function is actually a tensor and ...
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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
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Electric field in QE calculation
I want to apply an electric field pointing in z-direction to a two-dimensional crystal residing in the xy-plane using Quantum Espresso. So far I noticed that there are two distinct ways to do so ...
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Band Structure from EIGENVAL in VASP
So I am trying to plot the band structure from the EIGENVAL file produced by VASP. I wrote this Python code:
...
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Quantum Chemistry software that can calculate nonadiabatic coupling vectors between excited states using DFT/TDDFT
I am looking for software that can calculate the first-order non-adiabatic coupling vector $$\vec \tau_{ij}=\langle \varphi_i|\nabla_R\varphi_j\rangle$$ between excited electronic singlet states using ...
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Why my values of dielectric function don't match litterature (For Yambo with Quantum ESPRESSO)?
I try to reproduce the dielectric function as the picture bellow using Yambo code but the values that I have found in y-axis are so much bigger [-1000,1500] compared to literature. I generated the scf ...
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How to plot the dielectric function calculated with Yambo?
I want to calculate the optical properties using Yambo.
I used Quantum ESPRESSO 7.0 with Yambo 5.1.0, but I'm facing an issue. When I generate the dielectric function (o.eps_q1_ip) for example the o....
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How to plot HOMO-LUMO diagram using python?
I'm trying to create a HOMO-LUMO diagram for a presentation, similar to the below figure from ResearchGate. I would like to learn how to do this with Python if possible, since I know this language (...
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What is the ibrav value of a rhombohedral structure?
I have a rhombohedral structure
The SYSTEM and CELL_PARAMETERS blocks looks like this:
&SYSTEM
ibrav = 0
A = 6.058435171
...
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