Questions tagged [from-phys-se]

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11
votes
3answers
180 views

How does a beginner condensed matter theorist working on real materials, get up to speed?

I asked this on Physics.SE and got recommended here. More precisely, as a condensed matter theory PhD student, I am often overwhelmed by the wide variety of chemical formulas that experimentalists ...
3
votes
1answer
98 views

Simplifying double integrals of isotropic functions

Cross-posted from physics SE. I am studying statistical mechanics, and I am studying ideas surrounding potential of mean force and n-body density functions. In a derivation, they mention that $$-\left\...
10
votes
0answers
52 views

How to generate a complete set of doped (substituted) structures?

I'm trying to analyse doping in a certain material in low concentrations. I'm approaching the problem by taking crystallographic unit cell of that material, then expanding that to a 2x2x2 supercell ...
8
votes
0answers
73 views

Wavefunction magnitudes being degenerate everywhere on parameter space even though energy degeneracies occur at isolated points?

Cross-posted here. Consider the usual simple 2-level gapless graphene Hamiltonian in momentum-space where the energy dispersion is degenerate/gapless at a Dirac point: \begin{equation}\tag{1} {\small ...
10
votes
1answer
208 views

What is the right way to calculate <A><A>?

We asked a similar question somewhere else and someone advised trying here instead. How should we calculate $\langle A\rangle \langle A\rangle$ from data on dipole moments? It is a term in an ...
16
votes
6answers
2k views

How do I simulate the interaction between two atoms?

I want to build a rough atom interaction simulator, where pushes two (or more) atoms toward each other and they should behave physically correctly: attract, bond or repel with some force. So that is ...
8
votes
1answer
85 views

How are molecular rotational states modeled within the Born Oppenheimer Approximation for polyatomic molecules?

Molecular vibrational states associated with an adiabatic electronic state within the Born-Oppenheimer Approximation are typically defined by doing the harmonic approximation for the potential at an ...
11
votes
0answers
80 views

How to solve general wave equation and dispersion relation using Fourier series?

In this paper (open access), the authors used Fourier series with most general wave equation to find the dispersion relation. I am presenting some main equations as snippets to depict their solution. ...
7
votes
1answer
106 views

How is the error in a wavefunction related to the error in energy?

While studying the variational method in McQuarrie's Quantum Chemistry, I came across the following problem: to relate the difference between an approximation $\phi$ and the exact ground-state wave ...
12
votes
1answer
113 views

What does it mean to assign group operations to distinct sets for space groups?

I am trying to understand space groups in crystallography. In International tables for crystallography, for a nonsymmorphic space group, they list some symmetry operations. 8 of them are listed under ...
16
votes
1answer
1k views

Does the Schrödinger equation have unique solutions?

I am learning DFT and the Hohenberg Kohn Theorem of Existence. It says that there is a one-to-one correspondence between the external potential and the density. However the proofs that I have seen ...
7
votes
2answers
70 views

Combined effects of strain and doping on the electronic structure of semiconductors

I've read papers in DFT studies on band gap tuning in semiconductors and the usually studied methods are either through doping or application of external strain. But it is always just one or the other....
14
votes
5answers
522 views

DFT software package for a beginner?

I would like to do start doing some basic calculations using DFT. I am interested in solid state physics of strongly correlated materials in 3D (for example high temperature superconductors) or 2D (...
10
votes
0answers
95 views

How can I draw the energy bands for the first and second zones of Brillouin? Is it conductor or insulator? [closed]

I want to draw the energy ($E$) diagrams for a simple cubic cell of parameter $a$, where each atom provides two electrons for the almost free electron levels for planes [100], [110] and [111]. I ...
8
votes
1answer
351 views

Inversion symmetry in 2D materials

Transition metal dichalcogenides (TMDs) are composed of three atomic planes and often two atomic species: a metal and two chalcogens. The honeycomb, hexagonal lattice has three fold symmetry and can ...
8
votes
0answers
47 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 ...
11
votes
2answers
162 views

Separation of valence bands in transition metal dichalcogenides (TMDs)

The image below refers to a phenomenon that occurs in TMDCs (transition metal dichalcogenides) monolayers that allowed the development of valleytronics. Why are there separate bands of different ...
15
votes
2answers
326 views

Electron density arising from Slater determinant wave function

My textbook "Density Functional Theory of Atoms and Molecules" by Parr and Yang says that any N-representable density is derivable from a single determinantal wavefunction. A density $\rho$ ...
9
votes
1answer
83 views

Is there an anisotropy factor (g factor) for TDDFT absorption and circular dichroism calculations?

Experimentally, anisotropy factor is calculated by dividing the CD (circular dichroism) spectra by the absorbance spectra and multiplying by a factor of 32980 (in order to get a dimensionless quantity)...
13
votes
1answer
160 views

Can we "invert" Density Functional Theory through sufficiently accurate experiment?

The famous Hohenberg-Kohn theorems say that there is a one-to-one mapping between the many-body Hamiltonian, $\mathcal{H}$, of a solid and its ground-state electron density $\rho(\mathbf{r})$. As far ...
11
votes
1answer
196 views

Is there any software that can generate the electronic DOS of GaAs?

I want to calculate the density of states of GaAs conduction band (preferably each valley like Gamma, L and X). Is there any software available where I can easily generate DOS? Has the DOS of GaAs ...
16
votes
1answer
263 views

The Hund's J - Why can this be quantified?

I was reading on the implementation of Hubbard 'U' in Density Functional Theory. The Hubbard 'U' can be thought of as a parameter that accounts for the on-site electron-electron interactions in ...
17
votes
1answer
91 views

Converging the potential of a dilute binary alloy system using the Coherent Potential Approximation. What troubleshooting options could I take?

I'm trying to converge a dilute fcc alloy consisting of Cu and U, with the Uranium concentration at 0.01% and the lattice parameter of Cu, using Hubert Ebert's Spin Polarized Relativistic Korringa-...
24
votes
1answer
236 views

How do you calculate the "true" chemical potential in classical density functional theory?

In classical density functional theory, one traditionally calculates the chemical potential by taking the variational derivative, \begin{equation} \mu_{i} = \frac{\delta F}{\delta \rho_{i}}\tag{1} \...