Questions tagged [condensed-matter]
For all matters related to condensed matter physics.
108
questions
8
votes
1
answer
81
views
How to predict new Half Metallic materials with higher degree of spin polarization?
Using DFT calculations, how one can predict the new half metallic materials with higher degree of spin polarization. I want to know the steps which have to be followed in prediction of new materials. ...
- 2,481
8
votes
0
answers
102
views
What are some types of topologically-relevant band degeneracies in contemporary 2D condensed matter research? [closed]
In the study of 2D condensed matter systems, I have seen several kinds of band degeneracies. I call 'bands' the eigenvalues to the time-independent Schrodinger equation, solved over 2D k-space. By '...
- 2,131
8
votes
0
answers
110
views
Example of a standard/archetypal/simple 4-band gapped condensed matter model with analytic results? [closed]
I am looking to study Berry phase-like phenomena in a gapped 4-band material model. In particular, I want to numerically and analytically calculate the Abelian Berry curvature integral of each band ...
- 2,131
8
votes
0
answers
55
views
Symmetry of glide planes [closed]
I am trying to understand the symmetry elements of space group number 194 (P$6_3$/mmc), which is hexagonal and has 24 symmetry operations.
In the table of symmetry operations it says that it has three ...
- 1,733
7
votes
2
answers
130
views
How to get the directives of a slurm for my Quantum ESPRESSO calculations?
Context
I saw some examples of SLURM scripts on the internet like the one below:
...
- 1,451
7
votes
1
answer
227
views
Help with Definitions in Numerical Calculation of Multiband Berry Phase
In the third chapter of Vanderbilt's book, they discuss the so-called multiband parallel transport and provide a scheme for numerical calculations that is similar to the single band case (where the ...
- 2,131
7
votes
0
answers
43
views
The quantum spin Hall phase with Z2 = 0? [closed]
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 ...
- 2,763
7
votes
0
answers
192
views
How to fix gauge in Quantum ESPRESSO? [closed]
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 ...
- 2,131
6
votes
2
answers
996
views
POSCAR data file for a 2D system
I would like to understand how to calculate the band structure of the Graphene monolayer system using DFT. I am using VASP for material simulation. My question is how to write the crystal structure ...
- 61
6
votes
1
answer
132
views
About LaCrO3 space group stability
I found two space groups of $\ce{LaCrO3}$ material Pnma and Pm-3m. If someone is familiar with this material, please help to understand which phase is more stable. what are the factors that determine ...
- 643
6
votes
1
answer
280
views
Thermo-calc: Calculate precipitation driving force by parallel tangent construction
I want to calculate the difference in Gibbs free energies between a
Zr-Cu-Al liquid (composition - Zr 65 Cu 27.5 Al 7.5 at%) and the CuZr2
solid phase as a function of temperature (300 - 1000 K). In ...
- 61
6
votes
1
answer
75
views
Where is this extra plane coming from?
Why are there solid lines drawn connecting the solid circles after twinning has taken place? Ideally, that explains a real plane, isn't it? But why are we going to get a plane out of nothing if we ...
- 415
6
votes
1
answer
74
views
Imaginary time dependent operators: (anti)commutation relations
If I know trivial (anti)commutation relation for some operators (let's say Fermi operators), I can only use it if they are in the same moment of time. If I have their time dependence and they don't ...
- 161
6
votes
1
answer
220
views
How to formulate the second quantization of Dzyaloshinskii-Moriya interaction?
The Dzyaloshinskii-Moriya interaction (DMI) existing in the interface of the ferromagnetic insulator and the metal with strong spin-orbit coupling (SOC) is shown below.
Mathematically, it can be ...
- 14.7k
6
votes
1
answer
66
views
Example of a standard/archetypal/simple 4-band un-gapped condensed matter model with analytic results?
I am looking to study Berry phase-like phenomena in an un-gapped material model. However, I am having trouble finding a widely-used 4-band model with analytic expressions for wavefunctions and ...
- 2,131
6
votes
1
answer
123
views
Help with definitions in k-space twisted bilayer graphene model
I am trying to numerically do calculations using Eq. 8 of MacDonald's simple model for twisted Bilayer graphene. I only want to calculate the Berry phase. However, I don't think I have my definitions ...
- 2,131
6
votes
1
answer
57
views
Confusions in interpreting Dirac strings (wormholes) in Haldane's Hilbert space picture ft. two tori joined by strings at gapless points
I had a question about Haldane's wormhole interpretation (picture below). I believe he first proposed it in his paper Berry Curvature on the Fermi Surface: Anomalous Hall Effect as a Topological Fermi-...
- 2,131
6
votes
0
answers
45
views
Is it possible to evaluate rotational and vibrational partition functions for diffusion in the Eyring Theory of Absolute Rates?
Let us consider the usual expression for Diffusion processes and diffusion coefficients in the Eyring's theory:
$$D=\lambda^2k = \lambda^2 \frac{k_BT}{h}\frac{\Omega_\ddagger}{\Omega}e^{-\frac{\...
6
votes
0
answers
318
views
How to get a Wannier function for a tight-binding model numerically? [closed]
I have a question about construction of a Wannier function for a tight-binding model. Let's say we consider the tight-binding model of a 1D chain with two atoms (site A and B in a unit cell). In k-...
- 161
6
votes
0
answers
94
views
Constructing the symmetry operator from k.p Hamiltonian [closed]
I have a question regarding to how to construct an operator from k.p Hamiltonian. Maybe there are some problems in my understanding, I hope you can point me out and correct my description if I made ...
- 2,763
6
votes
0
answers
40
views
Example of 2D k-space models allowing interband transitions after a closed-loop trajectory? [closed]
I have been mainly exposed to 2D momentum-space condensed matter models in the context of Berry-related topology. I now want to study models where, if I take a closed loop in momentum space, I will ...
- 2,131
6
votes
0
answers
68
views
Value of density of state effective mass and transport effective mass to calculate conductivity [closed]
How can density of state effective mass and transport effective mass can be defined to calculate conductivity for a cubic system with parabolic but anisotropic dispersion relation? What will be the ...
- 1,575
5
votes
2
answers
102
views
What's the completeness relation of Bloch band?
Bloch's theorem can be stated as:
$$
|\Psi_{n\vec{k}}\rangle=e^{i\vec{k}\cdot\vec{r}}|u_{n\vec{k}}(\vec{r})\rangle \tag{1}
$$
where $|\Psi_{n\vec{k}}\rangle$ is the solution of single electron ...
- 14.7k
5
votes
2
answers
965
views
How to increase the number of CPUs in my computer?
I'm running my calculations using Quantum ESPRESSO on a 10th generation i7 computer (Dell) with Ubuntu.
When I run any calculation using the command ...
- 1,451
5
votes
1
answer
89
views
Property related with Berry curvature: $\Omega_{n,\mu\nu}=-\Omega_{n,\nu\mu}$
I read in David Vanderbilt's book named "Berry Phases in Electronic Structure Theory - Electric Polarization, Orbital Magnetization and Topological Insulators" the definition of Berry ...
- 1,733
5
votes
1
answer
183
views
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
5
votes
1
answer
120
views
Optimal Gaussian basis set for hydrogen atom in magnetic field
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 ...
- 183
5
votes
0
answers
47
views
Presence/absence of topologically protected edge states on the boundary of two topological insulators
A normal insulator is the same as vacuum because one can change the band structure from one to another without closing the gap, but for topological insulators (talking about 2D TI) like 1T'-TMDs or ...
- 51
5
votes
0
answers
99
views
About the mechanism of opening of the band gap in topological insulator with the inclusion of SOC [closed]
When we work on the topological insulator (protected by time reversal symmetry ), it is often said that the SOC is the main ingredient because it is a way to open a gap when the band inversion present....
- 2,763
5
votes
0
answers
99
views
Z2 topological index: Is this unconventional formula summed over just filled bands, or all bands? [closed]
The $\mathbb{Z}_2$ topological index is usually defined in terms of the Pfaffian of the overlap matrix, as defined by eq. 4 of Kane and Mele's paper:
$$
P(k)=\text{Pf}[\langle u_i(k) | \Theta | u_j(k) ...
- 2,131
5
votes
0
answers
272
views
Why does numerical computation of Berry curvature give me a correct Berry phase when it is supposed to diverge? [closed]
I implemented the standard numerical algorithm for calculating the Berry curvature in MATLAB. For a given 2D system, I can visualize the Berry curvature over parameter space. If I sum the Berry ...
- 2,131
5
votes
0
answers
50
views
What's the difference between dynamic and static strain aging? [closed]
I do understand how static strain aging occurs and why the yield point comes back if ample time is allotted after a loading and unloading cycles primarily due to diffusion of substitutional and ...
- 415
5
votes
0
answers
46
views
A doubt about extended dislocation [closed]
I wonder why this phenomenon occurs:
"Unlike unextended screw dislocations, the extended screw dislocations
define a specific slip plane, the {111} plane of the fault and it
will be constrained ...
- 415
4
votes
1
answer
149
views
How to restart an interrupted Quantum ESPRESSO calculation?
I was doing a vc-relax calculation and after 1 day the calculation suddenly stopped. Is there a way to restart it from previous interrupted calculation of do I have to restart from the beginning?
- 1,451
4
votes
1
answer
157
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 ...
- 113
4
votes
1
answer
122
views
Hubbard model SU(2) symmetry: manifest invariance
Could someone explain, is it possible to make Hubbard Hamiltonian manifestly SU(2) invariant? I know about the interaction term, but how would kinetic (hopping effect) term have to look like?
Here I'm ...
- 161
4
votes
1
answer
56
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?
- 93
4
votes
1
answer
82
views
Is there any useful application to estimating the expectation value for an Ising model without magnetic field?
In the same line of thoughts as this post, I am trying to understand better in which cases quantum computers could be useful to simulate materials under some constraints on what the quantum computer ...
4
votes
0
answers
55
views
When the T-even and T-odd conductivity tensor indicates the dissipationless transport?
In this paper, the authors discuss the three response relations or Ohm's law for spin/charge transport. The first one is the spin Hall effect described by:
$$J_j^i=\sigma_{s}\epsilon_{ijk}E_k \tag{1},$...
- 14.7k
4
votes
0
answers
58
views
How to plot downfolded bands from DFT bands?
Once you mapped the high symmetry points from primitive cell to the super cell, you need to plot the downfolded bands.
As we know in DFT output of band structure calculation we get a set of E vs k ...
- 113
4
votes
0
answers
44
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-...
- 543
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 ...
- 1,928
3
votes
1
answer
80
views
How to simulate a furnace computationally
I am trying to synthesize MoSe$_2$ crystals in a furnace with two temperature zones.
The problem is that the oven is not very wide, so the temperature of the hottest zone influences the temperature of ...
- 1,733
3
votes
2
answers
62
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 ...
- 113
3
votes
1
answer
70
views
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 ...
- 1,451
3
votes
0
answers
94
views
Help with Mathematica for optimizing a Gaussian basis set for a hydrogen atom in a magnetic field
This is a follow-up to my previous question: Optimal Gaussian basis set for hydrogen atom in magnetic field
Brief description of the problem
I would like to find the ground and excited states of the ...
- 183
3
votes
0
answers
45
views
Kohn anomaly and avoided crossing (or anticrossing/level repulsion)
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-...
- 395
3
votes
0
answers
34
views
Original reference for gapped chiral fermion k·p model?
In eq. 1 of this reference, the authors present the following Hamiltonian for the 2-band gapped chiral fermion model that can describe many systems including various semiconductors, N-layer graphene, ...
- 2,131
3
votes
0
answers
67
views
Symmetry for the low-energy effective model of Weyl semimetal
The low-energy effective model for Weyl semimetals (WSM) at a single Weyl point can be written as:
$$H_{w}=\chi \vec{k} \cdot \vec{\sigma}, \tag{1} $$
where $\chi$ is the chirality index, $\vec{k}$ is ...
- 14.7k
3
votes
0
answers
96
views
Why is there a deviation between the experimentally calculated values and theoretical done by DFT calculation? [duplicate]
If there was a deviation between the experimentally calculated values and theoretical determination done by DFT calculation, then what is the reason?
- 717