# Questions tagged [from-phys-se]

Questions that were first asked on Physics Stack Exchange.

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### 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)...
257 views

### High school student that wants to do DFT calculations

I originally asked this on Physics.SE but was suggested to ask here instead. I'm a high school student interested in material simulation. I want to do a project involving density functional theory to ...
44 views

### How is it possible for amorphous metal to have good magnetic properties with randomly arranged atoms?

Cross-posted on Physics.SE. It makes sense that something like grain-oriented electrical steel would have good magnetic properties (e.g., magnetic permeability). I'm envisioning magnetic field lines ...
82 views

### Why does the 𝛿 (delta) term exist in the density-density correlation for simple liquids?

Cross-posted from the PhysicsSE. I am reading Theory of Simple Liquids by Hansen and McDonald, and they in chapter 3, they describe the density-density correlation for a simple liquid in the grand ...
124 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 ...
1k views

### Mathematical expression of SCAN (Strongly Constrained and Appropriately Normed) constraints in DFT

(This question is originally posted on physics stackexchange, but someone suggested me to post on this site, so there you go) I'm compiling the mathematical expression of SCAN (Strongly Constrained ...
238 views

### What's the role of Berry curvature in quantized Hall effects? [closed]

Cross-posted and answered at Physics.SE. The quantized versions of the Hall effect include (ignoring fractional quantum Hall effect): Quantum Hall effect; Quantum anomalous Hall effect; Quantum spin ...
283 views

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

Cross-posted on Physics.SE. 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 ...
339 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 ...
140 views

### How to solve general wave equation and dispersion relation using Fourier series? [closed]

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. ...
118 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\...
75 views

### How to generate a complete set of doped (substituted) structures? [duplicate]

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 ...
264 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 ...
132 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 ...
3k 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 ...
236 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 ...
401 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 ...
162 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 ,  and . I ...
692 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 ...
135 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 ...
653 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} \...
858 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 $\rho$ ...
2k 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 ...
103 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-...
100 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....
3k 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 (...
66 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 ...