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Questions tagged [solid-state-physics]

Questions about solid state physics.

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5 votes
1 answer
74 views

Can conventional unit cell have higher symmetry than primitive cell for the same crystal?

This question arises from the last sentence of the first paragraph (see here) of the section "Formalism". If primitive cell can have lower symmetry, why don't the DFT results using these two ...
3 votes
1 answer
78 views

How to interpret defect formation energy diagram?

Why are formation energy diagrams typically plotted as a function of Fermi energy, and how should one interpret the changes in the x-axis before the charge state changes in these diagrams? Figure ...
4 votes
1 answer
80 views

Introducing a vacuum space in z direction for 2D monolayer calculations

Is the introduction of a vacuum in the z-axis necessary when utilizing a 2D monolayer material for Density Functional Theory (DFT) calculations in Quantum Espresso? (This is due to the fact that only ...
4 votes
0 answers
21 views

bandstructure calculation of two-dimensional ferrovalley (RuClBr) in quantum espresso

We try to calculate bandstructure of single layer RuClBr reported in fig.4 of 'https://pubs.rsc.org/en/content/articlelanding/2016/pq/d3nr00346a/unauth'. But our obtained bandstructure is not similar ...
3 votes
0 answers
50 views

convergence not achieved after 80 iterations [closed]

I am trying to run a scf calculations to obtain the band structure. However, in the output file, it is show that the convergence is not achieved after 80 iterations. ...
3 votes
0 answers
76 views

How did they calculate the indirect radiative recombination rate in this paper?

In this paper they calculated radiative recombination rates for Germanium using an effective mass model and I am trying to calculate the indirect spontaneous radiative recombination rate related to ...
2 votes
0 answers
61 views

Temperature effect on electronic properties

I'm particularly interested in studying how temperature affects electronic properties. However, I've been working with Quantum Espresso and its DFT + U functionality, and I'm struggling to understand ...
2 votes
0 answers
34 views

Symmetries and Permutation in the Slater-Koster matrix elements

In Wikipedia there is a list of Slater-Koster matrix elements, but not all of them are listed because "matrix elements that are not listed in this table can be constructed by permutation of ...
2 votes
1 answer
85 views

What is the Herman-Skillman method?

In the paper Norm-Conserving Pseudopotentials (1979), they refer to the authors' book for the all-electron(AE) calculation: ...
3 votes
0 answers
27 views

Compare transition matrix elements in molecules and solids

Is there a general trend such that transition matrix elements for electronic/excitonic transitions are larger/smaller in molecules than in inorganic solids or vice versa?
5 votes
0 answers
76 views

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 ...
14 votes
1 answer
6k views

Labeling of high symmetry points in Brillouin zone

A Brillouin zone is defined as a Wigner~Secitz primitive cell in the reciprocal lattice [1,2]. The construction of the first Brillouin zone for two different 2D lattices are shown below: The ...
7 votes
1 answer
128 views

In solids physics, how are Van Der Waals forces modelled?

I'd like to know how to treat VdW interactions among layers. Specifically I'm using Quantum Espresso and I'd like to know how VdW forces are implemented in the Kohn-Sham equation. Does it insert a $V \...
17 votes
12 answers
15k views

Is it better for me to study chemistry or physics?

I might decide to pursue material science. Aptitude and background I am from the UK, and for A-levels, I am studying Maths, Further Maths, Physics and Chemistry, and I am predicted decent grades in ...
6 votes
1 answer
286 views

Negative band gap in DFT calculations

I am performing DFT simulation (with Quantum Espresso) for a large number of crystalline materials to estimate their band gap energies. I am getting negative band gap values for many of them (...
3 votes
0 answers
62 views

Hilbert transform on the Bethe Lattice

In order to compute the local Green's function on the Bethe lattice, it is necessary to perform a Hilbert transform $$G_{loc}(\omega) = \int \frac{DOS(\varepsilon)}{\omega-\varepsilon} \text{d}\...
2 votes
3 answers
336 views

The "Tetrahedron method does not include variations of the Fermi occupations" Problem

I am doing computation of tetragonal CsPbBr3 perovskites. When I set ISMEAR = -5 I found such a problem: This problem is absent at ISMEAR = 0. What is the cause of the problem and how do I solve it?
8 votes
1 answer
522 views

Screened Coulomb interaction and its direct Fourier transform

I have a question concerning the screened Coulomb interaction in periodic systems. Many first-principle DFT codes provide the possibility to compute linear response functions, such as the irreducible ...
6 votes
1 answer
149 views

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?
10 votes
1 answer
634 views

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 ...
2 votes
0 answers
55 views

Antibonding, non-bonding or bonding hybridization [closed]

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), ...
8 votes
1 answer
823 views

Simulated STM Image with Quantum-ESPRESSO's pp.x

Context: I am an undergraduate "self-taught" noob when it comes to QE. (I've just been using online resources and textbooks thus far.) There are no QE or DFT experts at my university (I have ...
5 votes
1 answer
155 views

Can specifications of a second-order phase transition of a solid be obtained with the Hartree-Fock (or DFT) calculation?

At some temperature a crystal lattice of a solid can be rearranged or to say it more precise - got new positions of its cores. This phenomenon is well-known to be called a second-order phase ...
7 votes
1 answer
739 views

Why do we not get DOS by summing over all the PDOS?

If we sum over all the PDOS (Projected/Partial Density of States), will we have the total DOS or simply the DOS? This was not the case in my DOS and PDOS results for a simple Al atom. I am wondering ...
6 votes
2 answers
180 views

What makes the inhomogeneous electron gas more interesting than its homogeneous counterpart?

This question is asked in the context of the famous paper on DFT by Hohenberg and Kohn. What makes the inhomogeneous electron gas more interesting than its homogeneous counterpart?
13 votes
1 answer
2k views

What does a density of states (DOS) plot show?

I have plotted the density of states using GGA-PBE exchange correlation functional for magnesium silcide but I really do not know what the equations involved are in this process, and how they relate ...
3 votes
0 answers
66 views

Kohn anomaly and avoided crossing (or anticrossing/level repulsion) [closed]

Kohn Anomaly and Avoided Crossing (Anticrossing/Level Repulsion) are terms that are found to be used when discussing phonon dispersion. The former (see last paragraph, page 198) is related to electron-...
3 votes
1 answer
225 views

I'm considering to take an introduction course with textbook "Materials Science and Engineering: An Introduction", as a beginner QE user. Is it okay?

People, I am a beginner in material modeling (I am studing solid state in Quantum ESPRESSO) and I am having a lot of difficulty with basic terms like "k-points", "Miller Indices", &...
4 votes
1 answer
326 views

Optimzation for Large supercell

I am trying to optimize a copper supercell for the study of chalcones adsorption using Quantum ESPRESSO, however, the size of my supercell is large (>200 atoms) and QE can not handle it. What is an ...
2 votes
0 answers
53 views

Excited state frequency for periodic systems [closed]

Is there any way to calculate the excited state frequencies of a period system using DFT?
2 votes
0 answers
42 views

Can we create a phonon with a specific wavenumber that persists in the system for a long time? [closed]

The phonon number is not a conserved quantity, they add up as dictated by the dispersion relation until the Planck distribution is reached. However, I would need the k=PI/a phonons not to disappear ...
4 votes
2 answers
237 views

Which properties would you study to evaluate spatial confinement of a molecule

I'm modelling molecules confined within porous materials and I was wondering which molecular properties would you consider to access the confinement. Í'm thinking about looking into long-range ...
5 votes
1 answer
228 views

How to download METADISE code?

I have a (possibly trivial) question regarding the METADISE code. I can find the documentation related to this code, but I cannot find the download page or tarball anywhere. Can someone kindly share ...
5 votes
1 answer
168 views

How to find which atoms/bonds contribute to the particular section of band structure?

In this paper, in the first sentence of page no.6723, the authors attribute a particular section of band structure (in momentum space) to the bonds/ atoms in real space. I would like to know methods ...
9 votes
0 answers
140 views

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 ...
3 votes
2 answers
71 views

What happens to the position coordinates of the nearest neighbors in supercell studies?

Can anyone tell what happens to the position coordinates of the nearest neighbors when we choose to study supercell of the same material. That remains intact or any changes will be there? For example ...
5 votes
0 answers
55 views

The polarization lattice of a non-polar one dimensional chain [closed]

I have been trying to understand the concept of dielectric polarization in material science mostly by following Nicola Spaldin's lecture notes I am confused by the claim that the polarization of a non-...
4 votes
1 answer
293 views

How to map high symmetry points from primitive cell to conventional cell?

We usually plot electronic bands with the help of high symmetry points of the irreducible zone of primitive cell of particular material. But if we want to plot bands with conventional cell, we have to ...
6 votes
0 answers
582 views

How to get a Wannier function for a tight-binding model numerically? [closed]

I have a question about construction of a Wannier function for a tight-binding model. Let's say we consider the tight-binding model of a 1D chain with two atoms (site A and B in a unit cell). In k-...
11 votes
1 answer
202 views

Methods to determine the vacuum level in 2D compounds in the presence of dipoles

When 2D compounds have a dipole, the potential distribution becomes linear (the left panel of the figure). After considering the dipole correction, the potential has two plateau regions in the vacuum (...
8 votes
1 answer
341 views

Can deformation potential theory be applied to 2D and 1D systems?

I was pointed towards the use of the Deformation Potential (DP) theory to calculate the electron relaxation time in a previous question. However, I still have a doubt regarding its applicability to 2D ...
3 votes
0 answers
52 views

Cutoff energy in Quantum ESPRESSO calculation [duplicate]

What is cutoff energy in solid state calculations? I would just like a detailed explanation and the applicable formulas!
9 votes
1 answer
229 views

How to find the Cauchy stress tensor in solids using ab-initio methods?

I want to find the Cauchy stress tensor in certain materials with ab initio methods. I already have the analytical form of my own definition of "energy" and "forces" (not from DFT),...
11 votes
1 answer
324 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 $$ \...
6 votes
1 answer
343 views

What Wyckoff position to put in Input file of Unit Cell of TiCoSb?

$\ce{TiCoSb}$ has Wyckoff position as ...
6 votes
0 answers
252 views

How to define ferrimagnetism in Quantum ESPRESSO [closed]

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 ...
8 votes
0 answers
108 views

Constructing an anisotropic crystal in WulffPack [closed]

I am trying to create an $\ce{LiFePO4}$ crystal in WulffPack. I have the surface energies of seven different surfaces from the paper [1]. When I input the same to WulffPack, it creates a structure ...
8 votes
2 answers
640 views

Mobility and chemical potential

I have been studying the Boltztrap2 software to calculate the thermoelectric properties of materials. However when following the tutorial given, the Seebeck coefficient is plotted against ...
11 votes
2 answers
1k views

Why the band structure of a slab is not smooth?

I am trying to calculate the band structure of a TiO2-Rutile slab, but the result I got is not very smooth, and the result shows it is an indirect gap material, but the bulk phase of TiO2-Rutile is a ...
4 votes
0 answers
31 views

Do the VBM and CBM have to be on the high symmetry point? [duplicate]

I am trying to generate the band structure of a slab, a lot of tutorials tell me that I need to generate the high symmetry K point path, but I am wondering that if the VBM and CBM have to be on the ...