Questions tagged [solid-state-physics]
Questions about solid state physics.
87 questions
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Quantum espresso pseudopotential convergence test
I generated a pseudopotential using atomic code(Quantum_espresso_6.7/atomic/src/ld1.x) and conducted convergence test. But as below, total energy tends to oscillation as ecut goes up.
(I performed a ...
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Are there existing methods for gamma-point phonon estimation in case of large unit cells?
I'm trying to estimate some crude gamma-point phonon frequencies for a material with a large unit cell (>150 atoms). My goal is to verify some general trends (e.g., redshift) between 3-4 material ...
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Why is it PT symmetry not TP symmetry for Kramer Degeneracy
I understand that, under time reversal symmetry $H_k$ is transformed to $H_{-k}$, and only when we are at the points where k=-k such as in 1D the 0 and $\frac{\pi}{a}$ we would have degeneracy. And if ...
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Understanding Oxidation States and Magnetic Moments in Multivalent Transition Metal Oxides
I’m reading some papers on using density functional theory (DFT) to study oxidation states in multivalent transition metal oxides, but I’m having difficulty interpreting the oxidation-state ...
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Is there a scriptable tool to determine whether two periodic structures are the same?
I'm doing some material search, in which I remove 2-4 atoms from a medium sized (~20 atoms) unit cell. I need to find all different combinations that are unique with respect to the translational, ...
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29
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What is the relationship between electron-phonon coupling and nonadiabatic effects?
We know that under the Born-Oppenheimer (BO) approximation, the motion of nuclei and electrons is decoupled. However, when there is a degeneracy between potential energy surfaces, the nonadiabatic ...
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To what does ibrav correspond?
Compound has cif which is cubic in structure. Upon converting it to scf using input generator, it turns to primtive cell. When it is vc-relaxed it remains cubic with a bit distortion.However, when it ...
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In general: How to calculate effective mass from a bandstructure?
How to calculate the effective mass of silicon for the two cases: valence band maximum and valence band minimum (both at gamma point)? Any general procedure would be great to see.
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How to determine if hybridization takes place between orbitals in an ab initio calculation using Quantum ESPRESSO?
I'm using Quantum ESPRESSO to determine the electronic properties of systems. Now I want to confirm if hybridization takes place between orbitals. I have generated density of states and projected ...
- 453
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287
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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 ...
user10165
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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 ...
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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 ...
- 731
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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 ...
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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.
...
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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 ...
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71
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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 ...
- 101
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40
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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 ...
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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?
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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:
...
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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 ...
- 1,637
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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 \...
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418
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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 (...
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76
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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}\...
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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?
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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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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 ...
- 624
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57
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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), ...
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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 ...
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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 ...
- 1,027
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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-...
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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?
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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 ...
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425
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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 ...
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Excited state frequency for periodic systems [closed]
Is there any way to calculate the excited state frequencies of a period system using DFT?
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286
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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", &...
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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 ...
- 437
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
- 123
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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-...
user5405
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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 ...
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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 ...
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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-...
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398
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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 ...
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54
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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!
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264
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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),...
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What Wyckoff position to put in Input file of Unit Cell of TiCoSb?
$\ce{TiCoSb}$ has Wyckoff position as
...
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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 ...
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