Questions tagged [periodic-system]

Refers to a model which is treated as infinitely repeating, for example so as to use plane-wave basis functions and capture long-range electrostatic interactions.

Filter by
Sorted by
Tagged with
8
votes
0answers
126 views

transition dipole matrix element

When doing DFT calculations of periodic solids, from either $\mathbf{k \cdot p}$ perturbation theory or simply using the trick $\mathbf{r} \rightarrow i\partial_{\mathbf{k}}$, one can obtain $$ \...
10
votes
1answer
78 views

Pattern X-Ray Diffraction Fitting

Assuming I have an experimental powder XRD spectra and I have a number of computational structures without any knowledge of which is correct, how can I simulate the powder XRD spectra? Once I have ...
10
votes
0answers
157 views

Orbital magnetization in periodic solids

The orbital magnetization in periodic solids has been nicely described by the so-called modern theory of magnetization [1,2,3,4]. $$\tag{1} \mathcal{M}_{orb} = -\frac{1}{2} \Im \sum_{n,\mathbf{k}} f_{...
14
votes
3answers
356 views

When do I use the lattice parameters obtained computationally vs experimentally?

I have been trying to simulate the properties of Bi2Se3. But the lattice parameters given in Materials Project (which I believe is obtained computationally) is inconsistent with that of experimental ...
11
votes
2answers
307 views

Moving from VASP to CASTEP for bulk crystal and surface calculations

Can someone that works with CASTEP and VASP explain to me how a workflow might change between the two programs? I am very familiar with VASP but have not used CASTEP before. As an example, assuming ...
17
votes
1answer
527 views

Why is the band structure of a supercell more dense than for simple cell?

In order to do DFT calculations of metallic alloys, the start point is a supercell, whose atoms are changed to match the desired stoichiometry. Gold and Silver, for example, both have FCC structure. ...
19
votes
4answers
409 views

What is the status of graphics processing units in plane-wave DFT?

A few years back, I performed a few calculations of metallic slabs using VASP and the Atomic Simulation Environment (ASE). I'm by no means an expert, but I noticed that the calculations were very CPU ...
26
votes
1answer
421 views

How accurate are the most accurate calculations?

Taking into account the fact that the theory of quantum gravity does not exist and the QED calculations are not possible for most realistic chemical systems, what levels of accuracy can we expect from ...
20
votes
2answers
120 views

How are charge transfer processes modeled in materials?

I'm interested in looking at current flow across a nanoscale junction, specifically a pair of electrodes linked by a molecular bridge. How is this sort of problem typically approached? I'm vaguely ...
30
votes
3answers
501 views

What are the positives and negatives of periodic DFT codes that don't use plane-wave basis sets?

Most periodic density functional theory (DFT) codes use plane-wave basis sets in conjunction with three-dimensional periodic boundary conditions. In contrast, for molecular systems of finite size, ...
20
votes
3answers
358 views

How to do periodic DFT calculations using Quantum ESPRESSO?

I have only done quantum mechanical computations using non-periodic wavefunctions. I'd like to try to periodic-wavefunction density functional theory. Quantum ESPRESSO seems like a good package ...