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Questions tagged [condensed-matter]

For all matters related to condensed matter physics.

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How to numerically calculate quantum state distance using quantum metric?

In Ran Cheng's review of the quantum geometric tensor, eq. (11) gives the tensor as: $$ Q_{\mu\nu}=\sum_{n\neq 0}\frac{\langle\phi_0|\partial_\mu H|\phi_n\rangle\langle\phi_n|\partial_\nu H|\phi_0\...
TribalChief's user avatar
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8 votes
1 answer
87 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. ...
UJM's user avatar
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8 votes
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126 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 '...
TribalChief's user avatar
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8 votes
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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 ...
TribalChief's user avatar
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8 votes
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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 ...
Carmen González's user avatar
7 votes
1 answer
204 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 ...
chemdamned's user avatar
7 votes
1 answer
324 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 ...
TribalChief's user avatar
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7 votes
1 answer
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Force fields for generating **Co3O4 and Fe3O4 structures in LAMMPS

I am working on a project that requires generating a large dataset of Co3O4 and Fe3O4 structures under various temperatures and pressures using LAMMPS. The structures will be used for training machine ...
li jiwei's user avatar
7 votes
1 answer
172 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 ...
Mam Mam's user avatar
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0 answers
45 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 ...
JensenPang's user avatar
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7 votes
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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 ...
TribalChief's user avatar
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6 votes
2 answers
2k 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 ...
phdstudent's user avatar
6 votes
1 answer
137 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 ...
poonam sharma's user avatar
6 votes
1 answer
116 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 ...
Carmen González's user avatar
6 votes
1 answer
438 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 ...
Sachin Muley's user avatar
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 ...
user586228's user avatar
6 votes
1 answer
86 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 ...
Bojan Obradovic's user avatar
6 votes
1 answer
413 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 ...
Jack's user avatar
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6 votes
1 answer
73 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 ...
TribalChief's user avatar
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6 votes
1 answer
156 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?
chemdamned's user avatar
6 votes
1 answer
185 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 ...
TribalChief's user avatar
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6 votes
1 answer
70 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-...
TribalChief's user avatar
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6 votes
0 answers
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Modelling a porphyrin with a metal with just the p_z and d orbitals

We have a porphyrin-like molecule with a transition metal atom in the center, like the one shown in the figure. Consider first the porphyrin without the metal. In such a case, several orbitals around ...
Qwertuy's user avatar
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6 votes
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56 views

Is it possible to evaluate rotational and vibrational partition functions for diffusion in the Eyring Theory of Absolute Rates? [closed]

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{\...
Giuseppe Basile's user avatar
6 votes
0 answers
598 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-...
Ricky Pang's user avatar
6 votes
0 answers
124 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 ...
JensenPang's user avatar
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6 votes
0 answers
41 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 ...
TribalChief's user avatar
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6 votes
0 answers
70 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 ...
Shalini's user avatar
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5 votes
2 answers
1k 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 ...
Camilla's user avatar
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5 votes
2 answers
188 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 ...
Jack's user avatar
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5 votes
1 answer
948 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?
Camilla's user avatar
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5 votes
1 answer
81 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 ...
AbPhys's user avatar
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5 votes
1 answer
104 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 ...
Alpha_Roy's user avatar
  • 123
5 votes
0 answers
40 views

About alignment of 2D monolayer band structures

I need to do the alignment of band structures of one 2D monolayer. I have created some vacancies in the 2D monolayer using VASP and calculated the band gap values (GGA) corresponding to different ...
Poonam Sharma's user avatar
5 votes
0 answers
58 views

Strongly Correlated Materials: Theoretical Frameworks, Computational Techniques, and Machine Learning Breakthroughs in Matter Modeling

This is more of an opened discussion, recommendations, and experts views on the Strongly correlated materials. Exploring the behavior of strongly correlated materials poses significant challenges in ...
Jaafar Mehrez's user avatar
5 votes
0 answers
59 views

Presence/absence of topologically protected edge states on the boundary of two topological insulators [closed]

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 ...
Runnong Zhou's user avatar
5 votes
0 answers
195 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....
JensenPang's user avatar
  • 2,903
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-...
user avatar
5 votes
0 answers
140 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) ...
TribalChief's user avatar
  • 2,361
5 votes
0 answers
412 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 ...
TribalChief's user avatar
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5 votes
0 answers
70 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 ...
user586228's user avatar
5 votes
0 answers
48 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 ...
user586228's user avatar
4 votes
1 answer
116 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 ...
Camilla's user avatar
  • 2,199
4 votes
1 answer
306 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 ...
Alpha_Roy's user avatar
  • 123
4 votes
1 answer
223 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 ...
Bojan Obradovic's user avatar
4 votes
1 answer
58 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, ...
TribalChief's user avatar
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4 votes
1 answer
148 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 ...
Marco Fellous-Asiani's user avatar
4 votes
1 answer
129 views

How to read UPF pseudopotential for ultrasoft pseudopotential simple in a fortran program

I'm currently working on calculating semiempirical local and nonlocal matrix elements for Ga. To proceed with my calculations, I need to extract specific parameters from the UPF (Unified ...
Raj Kumar Paudel's user avatar
4 votes
0 answers
46 views

Phonon dispersion calculation of graphene with ASE

I'm trying to use the package ase.phonons to calculate the dispersion relation bands and the DOS, I followed the example of the documentation for Al and went well for the diamond case. For some reason,...
Rob Lut's user avatar
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4 votes
0 answers
40 views

Where can I read about Valleytronics?

Where can I read about Valleytronics? Are there any good books or review papers or influential papers on this topic? The question was also posted at the Physics site.
Rich Hard Fine Man's user avatar